Mountain Area Forecast ( July 11-15 )

Heavy To Excessive Rainfall Will Be Possible At Times This Week Amid A High Moisture Content Air Mass

The Storm Prediction Center Has Updated For A Slight To Marginal Risk For Severe Thunderstorms Between 8:00 AM Thursday and 8:00 AM Friday ( July 14-15 )

*A Marginal Risk is currently forecast to continue through Friday into early Saturday from the Cumberland Mountains southward.

A heavy to excessive rainfall potential will continue to be a weather concern in coming days, along with the potential for strong-severe thunderstorms by late week ( July 14-15 ).  A front is likely to stall across the area by this weekend to continue the daily chance for showers & thunderstorms.

**Depending upon where the boundary stalls, an increased risk for heavy-excessive rainfall may arise by late Friday into Saturday as very light winds develop aloft for slow storm motion on anything that develops.

Overnight Into Tuesday Morning

Partly to mostly cloudy with a chance of hit-miss showers and thunderstorms.  Areas of dense fog.  SW to WSW winds 5-10 mph on mid-upper elevation mountain ridges.  Temps in the upper 50s to mid-upper 60s ( mildest along exposed middle-upper elevation ridges and plateaus ).

Tuesday Afternoon

Showers & downpours in thunderstorms becoming likely.  SW winds 5-15 mph, with higher gusts.  Temperatures in the 60s to lower 70s in upper elevations to the mid-upper 70s ( warmer south toward the Tri-Cities ).

Tuesday Night Into Wednesday Morning

Chance of a shower or thunderstorm.  Areas of dense fog.  Winds WSW-WNW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges.  Temperatures widespread in the 60s.

Wednesday Afternoon

Chance of showers & downpours in thunderstorms.  Humid.  Winds SW-W at 5-10 mph, with higher gusts.  Temperatures varying from 70s in upper elevations to the low-middle 80s  ( warmer south toward the Tri-Cities ).

Wednesday Night Into Thursday Morning

Chance of showers & thunderstorms.  Humid & hazy with areas of dense fog.  SW-W winds 5-15 mph along mid-upper elevation mountain ridges.  Temps in the 60s to lower 70s.

Thursday Afternoon

Showers & thunderstorms likely.  Some storms may be strong to severe. Winds SW-WSW 5-10 mph, with higher gusts.  Warm & humid with temperatures varying from 70s in upper elevations to the 80s across low-middle elevations.

Thursday Night Into Friday Morning

A chance of showers & thunderstorms, especially during the early evening.  Areas of dense fog.  Winds SW-W 5-10 mph on mid-upper elevation mountain ridges & plateaus.  Mild with temperatures in the 60s to around 70 degrees.

Weather Discussion ( July 9-14 )

Thursday Overnight Notes

For days now models have been showing a very unstable air mass developing across the mountain region on Thursday, with high CAPE and low LI values combined with a bounty of moisture for potential water loading of downdrafts.

Debris clouds from upstream convection or early development of clouds-storms over the mountains could alter this by keeping the air cooler and more stable.  Something that will have to be tracked through Thursday into Friday to see how it unfolds.

It is hard to conceive that at least a few storms will not go severe, or be very strong, amid this type of air mass.  The main thing that is needed will be a trigger to initiate convection, with the terrain plus outflow boundaries from activity to the northwest & north as well as an actual surface boundary all being potential low-level triggers for convective firing.

Although downpours will certainly occur with any storms Thursday into Friday, the late Friday into Saturday period is currently catching my eye as parameters for local areas of heavy-excessive rainfall will increase.

Mean winds aloft drop under 10 knots by later Friday into Saturday within the surface-8 km layer as air remains very moisture ( 1.50″ to 2.00″ of precipitable water ).

Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings that may be needed during the Thursday-Saturday period of July 14-16.

Previous Discussion

Gorgeous weekend conditions graced the Cumberland Mountains with day-time MAXS in the 70s to lower 80s coupled with nights in the 50s and 60s.

I measured 4.10″ of rain at Big Cherry Lake Dam on Saturday, which had fallen during the previous week, amid frequent showers and downpours in thunderstorms.

*The lake level was still below the Dam spillway with 127+ Million gallons of water having been released from the lake during June to augment flow on the Powell River ( allowing room for the lake to still hold back run-off ).

Temperatures at highest elevations barely broke 70 degrees on Saturday & Sunday ( July 9-10 ), with 71.8 degrees being the weekend MAX observed at 4031 feet on Black Mountain.

Although several trees were blown down in the area the damage was spotty in nature and not widespread, as was  the case for folks lee of the mountains in the Great Valley.

Some gully washing downpours have been observed Monday, with a much better coverage of showers & downpours in thunderstorms  expected to develop Tuesday and periodically there-after during the remainder of this week-weekend and likely into next week.

Like last week, models continue to vary from run to run on where and how much rain will fall.  A repetitive pattern in a high moisture content air mass suggests some places will receive heavy to locally excessive rainfall.

The pattern during Summer 2016 ( June-July ) has been very consistent, especially since mid-late June, with a 500 MB air flow pattern very close to what MEAN 51-Member European Ensembles are forecasting during the next 10 days.

This being especially true if combining DAYS 1-5 with DAYS 6-10, such that the MEAN is very close to the Observed Composite MEAN graphic illustrated above for the June 22 to July 9 period.

The notable difference being a vertical expansion of the atmosphere across the nation as we enter what is often, climatologically at least, the hottest part of summer.

The hottest conditions so far during Summer 2016 ( above ) have been centered over the central-western USA, with a general W-WNW-NW flow into this region.

This type of pattern is forecast to continue during the next 10 days, with tendencies for increasing NW flow during the 5-10+ day period.  This implies that more organized clusters of thunderstorms will become likely, some with a damaging wind potential to accompany heavy rainfall during the mid-late July period.

NOTE I use the MEAN of the 51-Member European Ensembles since they are BY FAR ( and have been ) the most stable outward in time, and nothing suggest’s that they will not continue to be.

Part of, or superimposed upon, the above pattern has been developing drought across the southeastern USA into the Tennessee Valley and southern Appalachians.

*Differences being locally exemplified by nearly as much rain in the High Knob Massif since May 1 ( beginning of the convective season ) as observed in the Tri-Cities during the entire year.

The Bottom Line…Although there are always waxes and wanes that force daily weather changes, the big picture or synoptic-scale pattern remains consistent this summer and suggests that more of the same is upcoming for the mountain region during mid-late July.  This being superimposed upon drought that is trying to spread across the Deep South into parts of the Mountain Empire, as much wetter conditions and cooler mean temperatures continue from the local mountains ( High Knob Massif ) northward.

Meso-scale Notes On Monday – July 11, 2016

The High Knob Massif has acted as a cloud generation zone for booming thunderstorms, with gully washing rain, that have been over the adjacent Tennessee Valley Divide ( along the border of Wise and Dickenson counties ).

Note how the clouds in these individual frames can be seen extending back to the summit region and heads of the High Knob Lake, Big Cherry Lake, and Norton Reservoir’s basins.

An example of how wetness over the massif feeds into the over-lying atmosphere to develop towering clouds that go along with the atmospheric steering flow field to rain upon adjacent locations ( it happens all the time, but this is a nice current example that is visually obvious ).

*Total precipitation for 2016 has now reached around 40.00″ in the High Knob Massif versus less than 20.00″ for portions of the Great Valley only 30-35 or so air miles toward the south.

Any doubts about the massif impacting air flow can be eradicated by noting these nice lenticular mountain waves forming amid the wake zone ( fishtails on some above and stacked below ).

A really nice NASA visible showing clouds literally arising from the crest zone of the High Knob Massif and streaming across the southern portions of Dickenson and Buchanan counties into the extreme southern portion of West Virginia.

Mountain Area Forecast ( July 9-11 )

ALERT For Heavy To Excessive Rainfall At Times Into Next Week Amid A Persistence Pattern

A heavy to excessive rainfall potential with the possibility of dangerous flash flooding will continue to be a weather concern, especially from the Cumberland Mountains north and west, in coming days as waves of showers & downpours in thunderstorms periodically move across the region.

While many dry hours will occur, with a break from active storm clusters for much of this weekend, the storm pattern renews into next week.  Accumulative rain amounts over time will saturate the ground and make later activity more likely to cause water problems ( especially with any training or back-building of convection which occurs ).

*A general 2.00″ to 5.00″ of rain was observed across the mountain area during the July 3-8 period.

These statements are based on recognition of a repetitive synoptic-scale weather pattern and recent ( antecedent ) conditions producing numerous flash floods in the region.

Overnight Into Saturday Morning

A chance of showers & downpours in thunderstorms, especially toward morning.  Areas of dense valley fog.  SW to W winds 5-15 mph on mountain ridges & plateaus below 2700 feet.  WSW to WNW winds 10-20 mph, with higher gusts, on upper elevation mountain ridges.  Humid with temps mainly in the 60s.

Saturday Afternoon

Becoming partly sunny. Chance of a hit-miss shower or thunderstorm.  WNW winds 5-15 mph, with higher gusts.  Temperatures varying from 70s across upper elevations to the low-mid 80s ( hotter south toward the Tri-Cities ).

Saturday Night Into Sunday Morning

Partly to mostly clear ( some high clouds ).  Areas of dense valley fog.  W-NW winds 5-15 mph along upper elevation mountain ridges.  Cooler with temperatures varying from 50s in cooler mountain valleys to the mid-upper 60s.

Sunday Afternoon

Partly-mostly sunny. Chance of a shower or thunderstorm.  Light WSW to WNW winds mainly less than 10 mph.  Temps varying from 70s in upper elevations to the low-middle 80s ( hotter toward the Tri-Cities ).

Sunday Night Into Monday Morning

Partly to mostly clear.  Areas of dense valley fog.  Light winds.  Temepratures varying from mid-upper 50s to the mid-upper 60s ( coolest in mountain valleys ).

Clusters of showers & downpours in thunderstorms are expected to return by Monday into Monday Night and to continue periodically through most of next week.

Weather Discussion ( July 8-11 )

A vigorous storm line spread heavy rain, strong winds, and vivid lightning across the mountains Friday afternoon.

An outflow boundary was accompanied by strong and gusty winds in advance of the main storm line, part of a low-end Derecho that crossed the Ohio Valley, Appalachians-northern Tennessee Valley, producing torrential downpours of rain in Norton-Wise by 5:00 PM ( July 8 ) and local wind damage that increased in coverage lee of the Cumberlands into the Great Valley.

Thunderstorms began exploding across Kentucky into western parts of West Virginia during early afternoon, amid a steamy atmosphere loaded with water.

Over-shooting tops developed on some of the stronger storms, with Severe Thunderstorm Warning’s and Flood Advisories being issued for many counties from eastern Kentucky, western West Virginia and southwestern Virginia into the Great Valley.

Power outages were widespread across the region with numerous counties reporting current outages, on just the AEP Network, as of 11:03 PM Friday ( July 8 ).

Rainfall totals varied from around 0.50″ to between 1.00″-2.00″ as the storm cluster ( MCS ) passed.

*Local rainfall totals during July 3-8 have reached between 4.00″ and 5.00″, thus a concern for flooding will continue as storms increase in coverage into next week with more active clusters expected to rumble across the mountain landscape.

Meanwhile, it is hoped that much of this weekend will remain free of showers & thunderstorms after Saturday morning to mid-day ( behind a frontal passage ).

Mountain Area Forecast ( July 7-9 )

ALERT For Heavy To Excessive Rainfall At Times From This Week Into Next Week Amid A Persistence Pattern

Severe Thunderstorm Watch In Effect Until 9:00 PM

The Storm Prediction Center Has Issued A Enhanced Risk For Severe Thunderstorms Through Friday PM Into Friday Night – Main Severe Risk Is Wind Damage

A heavy to excessive rainfall potential with the possibility of dangerous flash flooding will continue to be a weather concern, especially from the Cumberland Mountains north and west, in coming days as waves of showers & downpours in thunderstorms periodically move across the region.

While many dry hours will occur, with a break from active storm clusters for at least part of this weekend, the storm pattern renews into next week.  Accumulative rain amounts over time will saturate the ground and make later activity more likely to cause water problems ( especially with any training or back-building of convection which occurs ).

These statements are based on recognition of a repetitive synoptic-scale weather pattern and recent ( antecedent ) conditions producing numerous flash floods in the region.  

Remainder Of Thursday Afternoon

Partly to mostly cloudy with scattered showers.  Chance of thunder.  Areas of dense fog across upper elevations.  Winds W-NW 5-15 mph, with higher gusts.  Temperatures varying in the 60s to lower-middle 70s ( warmer to the south into the Great Valley and Tri-Cities ).

Thursday Night Into Friday Morning

A chance of showers & downpours in thunderstorms.  Winds SW-W 5-15 mph on mountain ridges-plateaus below 2700 ft. WSW-WNW winds 10-20 mph, with higher gusts, on upper elevation mountain ridges.  Humid with temperatures in the 60s to around 70 degrees.

Friday Afternoon

A chance of showers & downpours in thunderstorms.  Some storms could be strong to severe with damaging winds and hail.  Winds SW to W 5-15 mph, with higher gusts.  Humid & hazy with temperatures varying from 70s to lower-middle 80s ( warmer south toward the TRI ).

Friday Night Into Saturday Morning

A chance of showers & downpours in thunderstorms.  Some storms could be strong to severe with damaging winds and hail.  SW to W winds 5-15 mph on mountain ridges-plateaus below 2700 feet.  WSW-WNW winds 10-20 mph, with higher gusts, along upper elevation mountain ridges.  Humid with temperatures in the 60s to lower 70s.

Weather Discussion ( July 5-9 )

Early Friday Afternoon

A dangerous severe thunderstorm-heavy rainfall setting is taking shape for the Mountain Area this afternoon into this evening ( Friday July 8 ).

Wind damage and power outages will be a significant threat along with any storms that train or back-build to generate very heavy rainfall ( even weak looking showers on Doppler have had downpours today as the air mass is water loaded ).

Warnings will be likely for some of this activity, so please remain alert to changing weather conditions.

Previous Discussion

Some majestic cloud formations have been observed through Thursday as abundant moisture and W-NW flow have combined to keep low clouds ( dense fog ) and many showers going across the High Knob Massif area.

Rainfall totals during this first week of July ( during the past several days ) have now reached around 3.00″ or more in upper elevations of the High Knob Massif, with widespread 1.50″ to 2.50″ amounts being observed across surrounding locations within Wise and Dickenson counties.

*Southern Kentucky and portions of middle Tennessee being the most recent targets for flooding rains.

Temperatures Thursday have remained in the 60s across mid-upper elevations above 2600 feet, with lower-mid 70s at low-middle elevations along and north of the High Knob Massif and Tennessee Valley Divide.

As of 4:42 PM ( July 7 ) the official MAX had reached 74.6 degrees at Clintwood 1 W in the Russell Fork Basin ( elevation 1560 feet ).

*The official MAX in Clintwood ended up reaching 76.1 degrees ( the July rainfall total climbing to 1.65″ ).

Focus now shifts toward additional storm clusters that are being forecast to develop overnight into Friday in advance of an approaching upper trough and surface front.

While a slight risk for severe thunderstorm development has been issued for the period from 8 AM Friday to 8 AM Saturday, recent runs of the HRRR and RPM models are showing overnight storm development.

Time will soon tell if these models are correct in this overnight storm development, with local 1.00″ to 4.00″+ rainfall amounts predicted.

*Remember is it difficult for models to handle convection, such that placement and timing of storms and MAX rainfall amounts prior to actual storm development is subject to change.

The threat for additional strong-severe thunderstorms in advance of a surface front must be respected by later Friday into Friday evening.

Please stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warning that may be needed.

Mountain Area Forecast ( July 5-7 )

ALERT For Heavy To Excessive Rainfall At Times From This Week Into Next Week Amid A Persistence Pattern

A heavy-excessive rainfall potential, with the possibility of dangerous flash flooding, will be the main weather concern for locations from the Cumberland Mountains northward in coming days as waves of showers and downpours in storms move across the region.  While many dry hours will occur, accumulative amounts will saturate the ground and make subsequent activity more likely to cause water problems.

It might seem unusual to issue a forecast statement as above, but in this case it is based upon recognition of a repetitive synoptic-scale pattern & recent ( antecedent ) conditions producing numerous flash floods across the region.  It is meant to raise awareness-alert levels that conditions favorable for flash flood generation will be present during a prolonged period of time.

Overnight Into Tuesday Morning

Intervals of showers & downpours in thunderstorms.  Areas of fog.  SSW-SW winds 5 to 15 mph, with higher gusts, along mid-upper elevation mountain ridges & plateaus.  Warm and humid with temps varying in the 60s to lower 70s.

Tuesday Afternoon

Periods of showers & downpours in thunderstorms.  Some storms could be strong to locally severe.  Humid  SW-WSW winds 5-15 mph, with higher gusts.  Temperatures varying in the 70s to lower 80s ( hotter south toward the Tri-Cities ).

Tuesday Night Into Wednesday Morning

A chance of showers & thunderstorms; otherwise, mostly cloudy, hazy and mild.  Areas of fog.  Winds SW-W 5-15 mph along mid-upper elevation mountain ridges and plateaus.  Temperatures widespread in the 60s to near 70 degrees.

Wednesday Afternoon

Hazy & humid.  A chance of showers & downpours in thunderstorms.  Winds SSW-SW 5-10 mph, with higher gusts.  Temperatures in the 70s to low-mid 80s ( hotter south toward the Tri-Cities ).

Wednesday Night Into Thursday Morning

Showers & downpours in thunderstorms.  Winds SW-W 10-20 mph, with higher gusts, mid-upper elevation mountain ridges.  Humid.  Temperatures in the 60s to lower 70s.

Weather Discussion ( July 4-7 )

Reference June 2016 Climate Data for rainfall totals ( more data to come soon ) as well as the new May 2016 Climate Data section.

Strong to severe thunderstorms blasted into the mountains late Monday afternoon with wind damage & power outages in numerous places to accompany downpours of rain.

Rainfall totals topped 1.00″ in Big Cherry Lake basin of the High Knob Massif as the storms developed and moved over into the Clinch and Holston river valleys.

More downpours of rain are pounding on roof-tops in Clintwood at 1:30 AM Tuesday as new development is propagating northeast from middle Tennessee and the southern portion of Kentucky.

For days now all models have been predicting heavy to excessive rainfall amounts through coming days, with placement & timing of the heaviest rain being the main uncertainty, with each model run being different with  respect to where the flooding rains occur.

The signal; however, is clear.  Heavy to excessive rains are likely to hit in places across the region this week into next week ( European Ensembles continue the pattern into next week ) as a high precipitable air mass hangs over the region.

*Some may think MAX totals of 8″ to 12″ are bogus; however, such amounts were being shown before the West Virginia flood event!

In the short-term, models suggest overnight into Tuesday and late Wednesday into Thursday as periods to watch for heavy to locally excessive rain amounts ( this does not mean that activity will not occur in between these waves ).

Due to the nature of convection, and the way it can alter the atmosphere, it will be necessary to update the forecast and this potential for heavy-excessive rainfall through coming days.  The big picture pattern; however, is clear with blazing heat to the south & southwest of the mountain area acting to generate and guide frequent clusters of showers and storms around its periphery into the Appalachians.

The Bottom Line…Now is the time, before the next flood, to be aware that another event or events are possible to likely in portions of the region this week into next week.  While there will likely be many dry hours, the accumulative nature of downpours over time will create the problem ( especially in locales having had 5.00″ or more of June rainfall and 10.00″+ of May-June rain ).

*Any place can flood if too much rain falls too fast, but antecedent rainfall amounts are important to look at with respect to where heavy rain could saturate the ground quicker ( i.e., it will take more rain to cause flooding in locations that were dry during June versus locations which were wet ).

Mountain Area Forecast ( July 3-5 )

The Chance For Showers & Downpours In Thunderstorms Will Be Increasing From  Independence Day Through This Week

Some thunderstorms could be strong to locally severe with the Storm Prediction Center issuing a slight risk for severe thunderstorms during Monday into Tuesday.

Severe Thunderstorm Watch In Effect Until 9:00 PM Monday ( Independence Day ) of July 4, 2016

A heavy-excessive rainfall potential, with the possibility of dangerous flash flooding, is increasing for locations along and now south of the Ohio River.  People living and driving along streams, and in flood prone locations, will need to be alert for the possibility of heavy rainfall from Monday PM Through Tuesday ( July 4-5 ) and again later in the medium range period ( into next week ).

Overnight Into Sunday Morning

Partly to mostly cloudy.  Chance of sprinkles or a shower.  Areas of valley fog.  E-SE winds at 5-15 mph, shifting S to W by morning, on middle to upper elevation mountain ridges.  Temperatures mainly in the 60s.

Sunday Afternoon

Partly to mostly cloudy.  Hazy and more humid with a chance for hit-miss showers & thunderstorms.  Light and variable winds.  Temperatures varying from the low-mid 70s in upper elevations to the lower-middle 80s ( warmer south toward the Tennessee Valley ).

Sunday Night Into Monday Morning

Partly to mostly cloudy.  Hazy.  Chance of showers & thunderstorms.  SSE-SW winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges.  Mild with temperatures in the 60s to around 70 degrees.

Monday Afternoon ( Independence Day )

Partly to mostly cloudy with a chance of showers and downpours in thunderstorms.  Some storms could be strong to locally severe.  SSW-SW winds 10-20 mph, with higher gusts.  Temperatures varying from 70s in upper elevations to the 80s across lower-middle elevations ( hotter to the south toward the Tennessee Valley ).

Monday Night Into Tuesday

A chance of showers & downpours in thunderstorms.  Some storms could be strong to locally severe.  SSW-SW winds 10 to 20 mph, with higher gusts, along mid-upper elevation mountain ridges & plateaus.  Warm & humid with temps varying in the 60s to lower 70s.

Weather Discussion ( July 2-5 )

Early Monday ( July 4 ) Discussion

Reference June 2016 Climate Data for a recap of recent rainfall data ( more information will be added in coming days ).

A battle is ongoing amid the atmosphere across the eastern USA as opposing forces clash, with developing drought to the south over the Tennessee Valley and southern portions of the Appalachians being in contrast to recent severe flooding in parts of West Virginia and central Virginia.

This makes the ultimate outcome of the next 1-2 weeks more uncertain than typical, with signals increasing for another major rainfall-flood & flash flood event for somewhere in the surrounding region.

The Storm Prediction Center has expanded the slight risk to now include much of the mountain region between 8 AM on Independence Day ( July 4 ) and 8 AM on Tuesday ( July 5 ).

In addition, the Weather Prediction Center has now issued a risk for excessive rainfall with the axis of heaviest rains in recent hours developing well south of the global models to the west in Kentucky ( with up to 5.00″ of rainfall reported in Murray, Ky., near Land Between The Lakes ).

The latest European Model, just completed at 3:00 AM on Monday, is forecasting the axis of heaviest rains to now be along and southward of the Ohio River across Kentucky into central-southern West Virginia ( impacting or being very close to the Cumberland Mountains in southwest Virginia ).

Rainfall will come in waves, with clusters of storms, during this week into next week along the periphery of blazing heat to the south and southwest of the region.

The Bottom Line…A prolonged period of stormy weather conditions are expected at times during the next 5-10 days, with clusters of showers & downpours in thunderstorms moving across the region.  Some of the storms could be strong to severe.  Ultimately, the greatest danger is likely to be heavy-excessive rainfall amounts.  Dangerous to potentially life threatening flooding could again occur somewhere in the region.

It is not yet possible to tell exactly where dangerous flooding may develop, so please stay tuned to NOAA Weather Radio and your favorite media sources for updates and possible watches and warnings that will be likely through coming days.

The European Model mean rainfall axis is from southern Indiana and northern-central Kentucky to central-southern West Virginia, versus the WPC which has the axis orientation more SSW-NNE.  In both it would again put the recently flood ravaged corridor within West Virginia at an enhanced risk.  Only time will tell where the actual corridor develops, with the entire region needing to remain alert given unseasonably high moisture values forecast through coming days ( always an ominous signal in July ).

Previous Discussion

A relatively nice Independence Day Holiday Weekend is being enjoyed amid the mountains, with MAX temps on Saturday ( July 2 ) only reaching the 70s to lower 80s in locations along and north of the High Knob Massif and Tennessee Valley Divide.

Although showers were only isolated in nature, clouds were abundant and helped to hold temperatures down with specific MAXS on Saturday reaching 76 degrees at Nora 4 SSE and 80.9 degrees in Clintwood.

The MEAN daily MAX temperature during June 1-28 at the official National Weather Service station, relocated again to the campus of the University of Virginia’s College At Wise, was 80.9 degrees     ( around 10 degrees Fahrenheit above average daily MAXS at the summit level of the High Knob Massif ).

So far during 2016 there have been no official 90 degrees days in Wise and no 80 degree days along the highest mountain crestlines amid the High Knob Massif and Black Mountain.

Focus now shifts to another dangerous weather pattern, similar in nature to the one that produced historic flooding in West Virginia during June, with renewed surges of heat and deep, tropical moisture streaming into the Ohio Valley and Appalachians.

SSW-WSW winds will be increasing across mid-upper elevations of the Cumberland Mountains in coming days as a low-level jet again develops to pump in moist, unstable air.

While individual models are varying in rainfall amounts and placement over the short and longer term periods, a trend for heavy to excessive rainfall along and north of the Ohio River is initially being given.

Once again locations from the Cumberland Mountains north are at highest risk for heavy rainfall during the upcoming week; however, this will need to be closely followed as the development of convection will alter the atmosphere over time and could skew amounts ( at least locally ) away from the MEAN corridor shown below.

The pattern continues to feature a notable heat ridge and developing drought to the south versus much cooler air toward the north.

Temperature differences are even showing up locally between the Cumberland Mountains and the much hotter Tennessee Valley, toward TRI-TYS-CHA ( as observed in recent days and weeks ).

Clusters of showers and downpours in thunderstorms will again fire along the periphery of blazing heat to the south and southwest, with movement along the edge of the heat dome during coming days.  Where training occurs, or any back-building, will dictate where dangerous, potentially life threatening flooding once again evolves.

While there will likely be a main corridor of highest flood threat, more localized flash flooding could also occur anywhere in the mountain region where thunderstorms train or back-build.

In addition to the increasing heavy rainfall threat, a chance for some thunderstorms to become strong to locally severe will have to be respected.

Please stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings which may be needed in coming days.

Mountain Area Forecast ( June 28-30 )

Overnight Into Tuesday Morning

Hazy & humid with light rain & drizzle.  Areas of dense fog, most widespread in locations along-north of the High Knob Massif & Tennessee Valley Divide.  Winds NW-NE at 5 to 15 mph along mid-upper elevation mountain ridges.  Temperatures widespread in the 60s.

Tuesday Afternoon

Partly sunny.  Small chance of a localized shower.  Skies becoming blue with decreasing haze late.  NW winds 5 to 15 mph.  Temps varying from low-mid 70s to lower-middle 80s ( coolest at highest elevations ).

Tuesday Night Into Wednesday Morning

Mostly clear.  NNW-NNE winds decreasing to generally less than 10 mph by morning on mountain ridges.  Temps from lower 50s to lower 60s.

Wednesday Afternoon

Partly to mostly sunny.  Beautiful blue skies with northerly winds 5-10 mph.  Temperatures varying from 60s at highest elevations to the middle 70s to around 80 degrees.

Wednesday Night Into Thursday Morning

Mostly clear.  Chilly in mountain valleys.  Light N-NE winds.  Temperatures varying from upper 40s to mid 50s in cooler mountain valleys to the upper 50s to lower 60s.

Thursday Afternoon

Partly cloudy.  Pleasant.  Small chance of a shower or thunderstorm.  Northerly winds generally around 10 mph or less.  Temperatures varying from 60s to lower 70s at highest elevations to the upper 70s to lower 80s.

A stormy weather pattern is likely to develop by the Independence Day Holiday Weekend into next week as heat & humidity increases to establish a temperature-moisture gradient across the region.  A heavy to locally excessive rainfall potential is being monitored for portions of the Mountain Region.  Stay tuned for later updates.

Weather Discussion ( June 27-30 )

Wednesday Evening ( June 29 ) Update

A gorgeous late June air mass graced the Cumberlands during June 29, with 50s to lower 60s in the morning giving way to pleasant 70s to around 80 degree afternoon temps.

Latest model runs are showing a better Holiday weekend for the Mountain Empire than in previous days, but a chance of hit-miss showers and thunderstorms will exist.

The operational European Model has come more in line with the MEAN of it’s 51-Member Ensemble group, with a shift to the north with the heaviest rainfall axis into next week.

While this might have been predicted from feedback of drought developing across the Tennessee Valley and parts of the southern Appalachians, it remains in flux and the Cumberland Mountains remain in play for the potential of heavy to excessive rainfall amounts next week ( along with locations to the north into the Ohio Valley & West Virginia ).

This recent trend does not bode well for flood ravaged West Virginia, with many praying for this current drying period to continue through the extended.

The Updated Bottom Line…While a chance for showers and thunderstorms will return from Thursday-Friday through the Holiday Weekend, recent model runs are not looking as wet as in previous days.

A very stormy period continues to be likely in the extended 5-10+ day interval, with a heavy to excessive rainfall potential looming for portions of the Ohio Valley and Appalachians.  Again, at this time, the precise corridor of main impact can not yet be determined despite a general shift northward by MEAN model guidance away from the Tennessee Valley ( the Cumberland Mountains remain in a potential target zone of training storm clusters ).

Stay tuned for later updates as models continue to work to figure out the pattern into the first week of July 2016.

Previous Discussion

Reference My 062716 Forecast Discussion for recent data on the West Virginia flood disaster.

While the terrible June 22-23 flood is being called a 1000 year event, it is important to note this may be true only in the corridor impacted. Many severe flood events have occurred in the Appalachians, with one of the worst and most widespread events striking during April 1977 ( 40 years from this coming April ).

Reference Flood Of April 1977 In The Appalachian Region for details on a major event that was much more widespread in coverage along the Appalachians, with 47 counties declared Federal Disasters along with 22 fatalities.  Many communities  across Wise, Lee, Dickenson, Buchanan, Scott, Bell, Harlan,  Letcher and Pike counties were devastated in addition to numerous communities in southwestern West Virginia.

Showers and downpours in thunderstorms developed to begin the new work week on June 27, with local rainfall totals topping 1.00″ in places.  Afternoon cloud bases lowered to obscure high ridges amid the high country.

While light rain, drizzle and low cloud bases linger tonight a drier and simply gorgeous stretch of weather conditions is expected to rule the mountain landscape during mid-week.

This period of weather should be enjoyed.

It is becoming clear in the modeling that another stormy period is upcoming as a temperature-moisture gradient again sets up a boundary along which clusters of showers and downpours in thunderstorms will roam.  Since the air mass to the south has not changed, this is worrisome given a high precipitable water air mass will be nearby.

This will be more of a WNW-ESE or W-E setting with thunderstorm clusters moving along the gradient.  What is yet to be determined is exactly where the gradient sets up.

The early trends seem to be ones to focus more on the southern Appalachians and Tennessee Valley versus locations flood ravaged in SE-Central West Virginia.

However, it is just too early to tell for sure.  More should be known in a few more days as initial action begins to form by late in the work week and the weekend.

The Bottom Line…A simply gorgeous mid-week stretch of weather conditions will give way to another stormy period by the Independence Day Holiday & next week.  The threat for heavy to excessive rains could again arise as a gradient sets up across the region with return of a high moisture content air mass, but the location of this can not yet be determined.

Stay tuned for updates in coming days.

Mountain Area Forecast ( June 26-28 )

ALERT For The Potential Of Torrential Local Rainfall Monday Into Monday Evening.  Some Storms Could Be Strong To Locally Severe.

The Storm Prediction Center Has Issued A Marginal Risk For Severe Thunderstorms Across The Mountain Area For The Period Between 8 AM Monday and 8 AM Tuesday ( June 27-28 ).

Overnight Into Sunday Morning

Mostly clear.  SE winds becoming SSW-SW at 5-10 mph, with higher gusts, along upper elevation mountain ridges.  Mild with temperatures from mid-upper 50s in cooler mountain valleys to the mid-upper 60s.

Sunday Afternoon & Early Evening

Partly cloudy.  More humid and hazier.  Chance of afternoon and evening showers or thunderstorms.  Local downpours.  Light S-SW winds generally less than 10 mph outside of any storms.  Temperatures varying from 70s in upper elevations to the lower-middle 80s.

Late Sunday Night Into Monday Morning

Partly to mostly cloudy.  Hazy & humid with areas of fog.  Chance of a hit-miss shower or thunderstorm.  Winds SSW to WSW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges & plateaus.  Warm.  Temps widespread in the 60s to around 70 degrees.

Monday Afternoon

 Showers & downpours in thunderstorms likely.  Some storms could be strong to locally severe.  Light & variable winds outside of storms.  Temperatures varying from the mid-upper 60s to the mid-upper 70s ( coolest at highest elevations ).

Monday Night Into Tuesday Morning

Hazy & humid with a chance of showers & thunderstorms.  Winds becoming WNW to NW at 5-15 mph along mid-upper elevation mountain ridges.  Temps widespread in the 60s.

Weather Discussion ( June 22-28 )

Thoughts, Prayers, and Condolences to families and friends losing loved ones are given to those impacted last week.

A preliminary signal for this larger event was observed in extreme SE Kentucky when flash flooding damaged 75-100 homes in Harlan County during June 21-22.  Rainfall totals up to 6.02″ were hand-measured 3 miles north of Harlan versus only 0.84″ atop Kentucky’s highest peak on Black Mountain ( Harlan 24 E ).

This skewed ( from climatology ) gradient of rainfall ( with less atop Kentucky’s highest and wettest terrain ) was again played out during the second and much larger event during June 23 when rain totals in the Greenbrier Valley ( for example ) were much greater than amid West Virginia’s wettest and highest terrain ( from the Pickens-Kumbrabow State Forest to Snowshoe-Canaan Mountain ).

While the pattern leading up to both of these episodes was well forecast, and I was both concerned and very aggressive with the forecasting, it must be understood that a pinpoint of where flash flooding or wind damage will occur is not typically possible in a convective pattern until after the thunderstorms actually develop on radar.

The high-resolution NAM 4 KM Model run at 8 PM on Wednesday, June 22, did the best job of forecasting rainfall with a MAX of up  10.00″+ over West Virginia ( just not over the counties where such amounts actually fell ).  It did have the heaviest rainfall zone, in general, properly placed on this particular model run.  By contrast, the HRRR Model in hours leading up to the main disaster had the heaviest rain forecast over northern West Virginia ( north of the Greenbrier ).  The centroid of actual convection building more to the southwest and south with the initial Mesoscale Convective Complex ( producing high winds ) than the HRRR predicted during hours after the 00z June 23 ( 8 PM June 22 ) initialization.

The 1981-2010 Annual Precipitation MEAN is listed as 39.30″ for White Sulphur Springs ( the above being for 1971-2000 ).

An excellent example of how convection skews settings is that the Covington, Virginia to White Sulphur Springs, West Virginia corridor is typically among the driest in both states over the long-term mean ( average annual precipitation in the 37.20″ to 40.40″ range ).

During the January to May period of 2016 just over 15.00″ of total precipitation had been measured in Covington, with around 16.51″ in White Sulphur Springs ( only around half as much as in wetter portions of the High Knob Massif  ).

During this event, around 3 times as much rain fell on White Sulphur Springs in just 12 to 24 hours as typically falls during an entire June ( 3.51″ ) at that location.

The 1981-2010 Annual Precipitation MEAN is listed as 37.80″ for Covington Filter Plant ( the above is for the 1971-2000 period ).

During the convective ( thunderstorm ) season it becomes important to understand that places which are the wettest  ( climatologically over the longer term ) may not receive the most rainfall, especially during any particular event when any place ( even those typically among the driest ) becomes a potential target for heavy to excessive rain.

An interesting, perhaps ironic, twist to these terrible events being that this excessive rainfall fell amid a large region of developing drought in the eastern USA ( particularly along much of the Appalachian chain ).

A drier air mass and welcomed break from the stormy pattern was observed Friday-Saturday ( June 24-25 ).

Focus now shifts toward the next weather systems which will be impacting the mountain region from late Sunday into the upcoming work week and first week of July.

The Storm Prediction Center has issued a marginal risk for severe thunderstorm development across the mountain region for Monday into early Tuesday.

A threat for heavy rainfall, which may be implicit but not an actual factor in severe thunderstorm criteria, may end up being the most important concern given that another high precipitable water air mass will be in place during Monday-Tuesday ( June 27-28 ).

I may issue an ALERT for this Sunday Night if I think this will be a significant concern for June 27-28 ( with another pre-signal being how convection may or may not form by later Sunday into Sunday evening as a litmus test ).

I will say that the pattern ahead remains a concern, with persistence of a WNW flow across the region and a gradual amplification once again.

This causes a cooling trend across much of the northern half of the nation and a shift to heat dome cores over Texas and the Pacific Northwest and West Coast of the USA.

This once again strengthens a north to south temperature gradient across the eastern USA.

The pattern upcoming, therefore, will feature hot and very humid air to the south and unseasonably cool, drier air to the north with a battle zone in between featuring an array of showers and downpours in thunderstorms.

The job for regional forecasters in days ahead, especially during the extended 5-10+ day period, will be to determine where this battle zone sets up shop ( likely with waxs and wanes in precise positioning ) since it will be the zone that could again feature heavy to excessive rainfall amounts.

Mountain Area Forecast ( June 22-23 )

ALERT For Severe Thunderstorm Development During Wednesday-Thursday.  A Major Wind Damage Event Is Likely Within Or Close To The Cumberland Mountains And Mountain Empire

Wind Damage, Large Hail, Vivid Lightning & Flooding Rainfall Will Be The Main Severe Threats.  This Could Result In Power Outages For Impacted Locations.

Updated at 6:00 PM Thursday – Individual supercell thunderstorms across Kentucky are forming into a squall line that will be the main feature of concern Thursday Evening-Night for counties across the Cumberland Mountains and Mountain Empire

A stormy weather pattern, anchored by a major heat dome to the west, is taking shape with strong-severe storms becoming likely during the Wednesday-Thursday period as part of a major severe weather outbreak.

Mesoscale Convective Systems ( large thunderstorm clusters ) are expected to develop, with potential for Derecho or near-Derecho Formation ( a long-lived wind damage producing system ).

More localized strong-severe thunderstorm development will also exist as dewpoints and instability increase through Wednesday. Please stay tuned to NOAA Weather Radio for possible watches and/or warnings that will be likely.

Tuesday Night Into Wednesday Morning

A chance of showers & thunderstorms.  SW-W winds 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges.  Temperatures widespread in the 60s.

Wednesday Afternoon Into Wednesday Night

Showers & thunderstorms likely.  Some storms could be strong to severe with wind damage and flooding rainfall.  SSW-W winds 10-20 mph, with higher gusts.  Temperatures varying from upper 60s-lower 70s across highest elevations to the upper 70s to lower 80s.  Very humid.

Thursday Morning Into Thursday Night

Showers & thunderstorms likely.  Some storms could be strong to severe with wind damage and flooding rainfall.  SW-W winds 10-20 mph, with higher gusts.  Temperatures varying from 60s to low 70s in the morning to the 70s to lower 80s into the afternoon.  Very humid.

Although details remain to be worked out, I have significant concern that a flash flood setting could also emerge across portions of the mountain area.

*NOTE that high-resolution models change radically due to the nature of convection over short-time periods.  Therefore, it is most important to FORECAST THE PATTERN in a setting like this and not depend upon any given model run.

Weather Discussion ( June 21-23 )

Early Thursday Afternoon Update

A Tornado Watch is now in effect for Dickenson and Buchanan counties until 10:00 PM Thursday ( June 23 ).

Remember that a WATCH means conditions are favorable for tornadoes IN AND CLOSE TO the watch area.

The atmosphere today is so unstable that there has been explosive thunderstorm development during the mid-afternoon, with radar indicating cloud tops soaring to more than 60,000 feet into the steamy atmosphere.

The Storm Prediction Center indicated that a watch would be coming during the early afternoon, which is no surprise given increasing instability ( high CAPE-moisture values to go along with SHEAR ) in presence of outflow boundaries generated by the overnight Thunderstorm Complex that passed just north and northeast of the Cumberlands.

More than 30,000 homes & businesses lost electricity across West Virginia on the AEP Network overnight into Thursday morning.

Meanwhile, a flash flood emergency has been declared in portions of the eastern mountains, from Richwood in Nicholas County into the Greenbrier County area.  Outside of that area at least 1 person has reportedly been swept away by flooding in West Virginia.  In fact, WSAZ-TV reports at least 30 flood rescues in progress across the state at 5:45 PM Thursday.

The updated risk region has the northern end of the Cumberland Mountains touching the Enhanced Risk.

Early Thursday Overnight Update

Counties along the Virginia-Kentucky border once again took the burnt of strong-severe thunderstorms Wednesday, with prolific lightning, heavy rain, and local wind damage.

Wednesday ( June 22 ) MAXS remained in the 70s in Norton-Wise and Clintwood ( 75 degree MAX ) as debris cloudiness coming in from thunderstorms toward the northwest, and subsequent storm development, held air temperatures down versus locations south toward the Tri-Cities ( where 85 to 90 degrees was common ).

A major thunderstorm cluster that is near the Maddox definition for a true Mesoscale Convective Complex or MCC formed Wednesday evening across the Upper Midwest.

Note the dramatic increase in size as denoted by colorized Infrared Satellite Imagery showing the expansion of cold cloud tops which are associated with deep convection ( thunderstorms ).

These are the most prolific lightning producing systems on planet Earth, so a tremendous “light show” is ongoing.  “Heat” lightning will be seen far to the south as the complex drops farther S-SE.

For some reason, perhaps some contamination of sounding data, short-range models like the HRRR resolved the storms better up until the 00z ( evening ) data was ingested.

Recent HRRR future Doppler forecast’s have lost the storm line over Illinois into Indiana.  So it becomes more “interesting” with respect to how far south and southwest the MCS-MCC develops versus a more eastward trend currently forecast by the HRRR.

Climatology shows that such systems typically build farther south and southwest ( toward the inflow side ) and turn more right of the general flow field over time ( as I noted previously, the MesoHigh or cold pool forces system relative low-level convergence to help dictate the propagation over time ).  The important area that HRRR recent runs have missed, over Illinois into Indiana, being the point outward from which there is beautiful upper divergence as seen on above Infrared images.

Numerous tornado and many wind damage reports have been documented from Illinois and Indiana into Ohio.

My thinking remains essentially unchanged, as despite what happens into Thursday morning it is very likely that new development forms during the afternoon-evening to renew the severe threat ( with wind damage and flooding rainfall remaining the primary threats outside of always dangerous lightning and localized hail ).

An outflow boundary from this MCS-MCC ( near Derecho ) system will act as a notable focus for new development Thursday, amid a very unstable air mass with high CAPE and instability.  This will likely, unless the area is very lucky, lead to a more widespread severe event Thursday versus that experienced Wednesday.

Continue to stay tuned to NOAA Weather Radio and your favorite media sources for more watches and/or warnings which will be likely once again Thursday.

Previous Discussion

Reference my 062116 Forecast Discussion for more details.

Strong to severe thunderstorms impacted portions of the mountain region during Tuesday as instability & moisture increased along and ahead of a surface frontal boundary.

Factors conducive to a major severe weather outbreak are now becoming better defined, with a serious threat of one or more clusters of severe thunderstorms.

Potential for a Derecho is increasing, with a major wind damage event coming close ( to the north ) or hitting the Cumberland Mountains by Thursday.

Meanwhile, a lead thunderstorm cluster currently from Iowa into Illinois could drop southeast and trigger strong to severe thunderstorm development Wednesday in advance of the next major storm complex.

One reason I have become very aggressive with this forecast is that even IF the main Derecho complex misses hitting the area directly, a major outflow boundary is likely to act as a focus for new severe thunderstorm development Thursday toward the inflow side ( warm-very unstable ) of the system across eastern Kentucky and southwestern Virginia.

Such a setting also increases the potential for flash flooding to develop, since a tendency for back-building convection is climatologically favored amid a more westerly 850 MB flow field ( beneath WNW flow aloft ) along any boundaries that are present to act as a low-level focusing mechanism ( in combination with terrain features ).

*Some homes were flooded in Harlan County during Tuesday amid an air mass that possessed a lower total water content than that expected Wednesday into Thursday.

The Bottom Line…A serious severe weather outbreak is likely to develop Wednesday into Thursday, impacting locations within or very close to the Mountain Empire.

Please stay tuned to NOAA Weather Radio and your favorite media sources for updates and likely watches and warnings that will be needed.

Mountain Area Forecast ( June 20-22 )

Reference My Latest Forecast Update At This Link

ALERT For Potential Of Severe Thunderstorm Development During Tuesday And Wednesday

Wind Damage, Large Hail, Vivid Lightning and Flooding Rain Will Be The Main Severe Threats ( This Could Result In More Power Outages For Impacted Locations ).  This Threat May Extend Into Thursday ( June 23 ).

A stormy weather pattern, anchored by a major heat dome to the west, is taking shape with the potential for strong-severe storms increasing Tuesday into Wednesday.

One or more Mesoscale Convective Systems ( large thunderstorm clusters ) are expected to develop from Tuesday into Wednesday, with some potential for Derecho Formation ( a long-lived wind damage producing system ).  Exact location and track of these thunderstorm clusters remains uncertain and will need to be predicted once storms develop on Doppler radar.

More localized strong-severe thunderstorm development will also exist as dewpoints and instability increase from Tuesday through Thursday.  Please stay tuned to NOAA Weather Radio for possible watches and/or warnings that may be needed.

Remainder Of Monday Afternoon

Partly cloudy.  Small chance of a shower or thunderstorm.  Winds W-NW at 5-15 mph, with higher gusts along middle to upper elevation mountain ridges.  Temperatures varying from low-mid 70s at highest elevations to the lower-middle 80s ( warmer south toward the Tri-Cities ).

Monday Night Into Tuesday Morning

Partly to mostly clear during the evening, then increasing clouds overnight into morning with a chance of showers & thunderstorms.  Winds SW to W at 5-15 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  WSW-WNW winds 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from middle-upper 50s to the mid-upper 60s ( coolest in mountain valleys with light winds ).

Tuesday Afternoon

Showers & thunderstorms becoming likely.  Some storms could be strong to severe.  SW-WSW winds 10-20 mph, with higher gusts.  Temperatures varying from the upper 60s to the upper 70s to around 80 degrees ( coolest at the highest elevations ).

Tuesday Night Into Wednesday Morning

A chance of showers & thunderstorms.  Some storms could be strong to severe.  SW-W winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temps widespread in the 60s.

Wednesday Morning Into Wednesday Evening

Showers & thunderstorms likely.  Some storms could be strong to severe.  SSW-W winds 10-20 mph, with higher gusts.  Temperatures varying from upper 60s-lower 70s across highest elevations to the upper 70s to lower 80s.

The risk for a large thunderstorm complex will be highest from Tuesday Night into Wednesday, with initial development expected to be upstream of the Appalachians followed by movement toward the mountains from the northwest.  Timing and trajectory ( track followed by the storms ) will have to be determined as the event gets closer.  Stay tuned for updates.

Weather Discussion ( June 18-22 )

A lovely stretch of June weather during the Father’s Day weekend is expected to end abruptly as the risk for showers and powerful thunderstorms increases significantly into Tuesday and Wednesday ( June 21-22 ).

My friend Wayne Riner captured a gorgeous sunrise above Long Ridge, in southern Dickenson County, to begin the work week.

With some vertical cloud development a hit-miss, localized shower or even thunderstorm can not be completely ruled out through this afternoon-early evening.  Chances remain low today and tonight in comparison to Tuesday when odds for shower-thunderstorm development ramp upward.

The entire pattern is being anchored by a heat dome centered over the southwest-central portion of the USA.

The initial increases in the risk for strong-severe storms will develop as a cold front sags southward into the region during Tuesday, providing a low-level focus for convection as the upper level flow diverges and streams across the Mountain Empire from the northwest.

However, what is really catching my eye is a surge of blazing heat that will be developing into Wednesday, setting up a huge temperature-dewpoint gradient from southwest to northeast across the Great Lakes and the Middle Atlantic region ( below ).

By early Wednesday a 20+ degree Celsius ( 38+ Fahrenheit ) temp gradient is being forecast between the Upper Midwest and eastern Great Lakes-Northeastern USA.  The thermal zone being defined well on the above model ( even though exact placement of its axis may vary some from what any given model is currently showing ).

 While thunderstorms Tuesday could become strong to severe amid a general northwest flow setting, and must be respected, the synoptic or large-scale pattern becomes even more favorable for large thundrstorm cluster ( complex ) development by Tuesday Night into Wednesday.

It is during this time that potential for a Derecho or near-Derecho cluster of thunderstorms will increase.  One reason for this is the presence of dry mid-level air ( shown above ) which research has shown to be a KEY factor in supporting wind damage producing bow echoes-Derechos.  The dry air promotes formation of a strong MesoHIGH or cold pool via evaporation aloft.  The cold pool acts to sustain the system by continuous formation and generation of low level convergence relative to the convective system ( evaporation into drier air aloft adding to downdraft momentum by making the air more dense ( heavy ) and aiding its plunge to earth ).  Terrain drag at the surface with downward and outward spreading air forces convergence ( or piling up ) of low-level air to drive and renew upward vertical motion ( lifting moist, unstable air to create condensation and complete a cyclic feedback process ).

The horizontal temperature gradient at the surface being a factor to strengthen winds aloft ( dictated by the thermal wind equation and the isallobaric component of the ageostrophic wind equation ) during any time of year, adding to the potential for downward momentum transfer to the surface in organized downdrafts.

It can not yet be known if the Mountain Empire will take a direct hit from a complex.  While large storm clusters do tend to move along 1000-500 MB thickness lines, and the 850-300 MB MEAN cloud-layer wind field, the ultimate movement is often dictated by the greatest system-relative low-level convergence ( forced by the cold pool ) which may or may not be in the same direction as the low-level jet.

*This may further be modulated by Supercell’s embedded within the MCS which adds additional complexity to propagation as has been suggested by Stephen Corfidi at the Storm Prediction Center.

Since the low-level jet often streams into such a system from the southwest, it is not uncommon for development to focus on the inflow side of the system which is often the southwest-southern, or forward, flank for a cluster embedded in NW-SE ( downshear ) flow.  While this is, of course, very important an assemblage of many MCS’s illustrates that ultimate movement is forced most by the cold pool produced by low-level convergence relative to the system ( and apparently modulated by embedded Supercells ).

Therefore, it may depart from what 1000-500 MB thickness and 850-300 MB MEAN cloud-layer pattern might predict and is best forecast by a Vector approach that takes into account cold pool forced low-level convergence with mean layer fields.

The Bottom Line…while the Mountain Empire is not currently within the slight or enhanced risk regions on Wednesday, it is too soon to know exactly how this will play out and it is likely that this risk graphic will change during the next couple of days as storms form and alter the atmospheric setting over time.

One or more thunderstorm clusters, with potential for a severe weather outbreak, is expected from Tuesday into Wednesday.  Localized strong-severe storms may also develop to impact more limited corridors along their paths.  Please stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings that may be needed from Tuesday into Thursday ( June 21-23 ).

Mountain Area Forecast ( June 17-20 )

Remainder Of Friday Afternoon

Mostly cloudy with a chance of showers and patchy drizzle.  Seasonally cool with temperatures in the 60s to low 70s for locations along & north of the High Knob Massif-Tennessee Valley Divide ( warmer south toward the Tri-Cities ).

Friday Night Into Saturday Morning

Cloudy with a chance of scattered showers during the evening-early overnight.  Becoming partly cloudy into morning.  Winds shifting ENE-SE at 5-15 mph on middle-upper elevation mountain ridges and plateaus.  Temperatures in the 50s to around 60 degrees.

Saturday Afternoon

Any clouds giving way to mostly sunny, blue skies.  Pleasant conditions.  ESE-SSE winds 5 to 10 mph, with higher gusts.  Temperatures varying from upper 60s to lower 70s at the highest elevations into the upper 70s to lower 80s ( warmer toward the southwest and south of the High Knob Massif ).

Saturday Night Into Sunday Morning

Mostly clear.  Winds SE-SSE 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temperatures varying from mid-upper 40s to the mid-upper 50s ( coolest within mountain valleys with calm winds ).

Sunday Afternoon

Mostly sunny ( some high clouds possible ).  Light SE to S winds.  Temperatures varying from the low 70s at highest elevations to the lower-middle 80s.

Sunday Night Into Monday Morning

Mostly clear.  Winds becoming S-SW at 5-10 mph along mid to upper elevation mountain ridges.  Temperatures varying from the 40s in cooler mountain valley to the 50s to near 60 across exposed ridges-plateaus.

Weather Discussion ( June 16-20 )

Beautiful mammatus clouds, forming on the bottom side of a large cumulonimbus anvil, were captured over western Lee County by photographer Harold L. Jerrell Thursday.

Rainfall with storms, as often is the case at this time of year, was not uniform with large variations across southwestern Virginia from nothing up to 1.00″ to 2.00″ .

Locations from central-eastern Dickenson County into Buchanan County and portions of Russell, Tazewell, Washington, Smyth and Grayson counties endured the strongest thunderstorms with power outages still ongoing as of 4:58 PM on Friday ( June 17 ).

A mostly cloudy, cooler air mass has dominated Friday, especially along and north of the High Knob Massif-Tennessee Valley Divide.

Some light showers and drizzle have occurred along with low cloud bases that occasionally obscure the highest ridges.

Friday ( June 17 ) temperatures have been much cooler with afternoon readings only in the 60s to lower 70s in locations along and north of the High Knob Massif & Tennessee Valley Divide.

*The 4:45 PM temperature of 70.7 degrees in Clintwood being down from a PM MAX of 72.8 degrees.  Air temps have hovered around 60 degrees at the summit level of the High Knob Massif during the afternoon.

The hottest air being suppressed to the south and west, with a major heat dome forming during the weekend into next week across southwestern-central portions of the USA.

A pleasant Father’s Day weekend is on tap with beautiful skies ( low dewpoints ) and seasonally cool nights.

A renewed surge of heat-humidity in advance of another cold front will bring the chance for more strong-severe thunderstorms by the Tuesday-Wednesday period of next week ( June 21-22 ).  Stay tuned for updates.