My Area Forecast ( May 31-June 2 )

Overnight Into Wednesday Morning

Partly to mostly cloudy.  Small chance of a shower or sprinkle.  Areas of valley fog at lower elevations.  Light and variable winds.  Temperatures varying from the upper 40s to lower 50s in high mountain valleys to the mid-upper 50s.

Wednesday Afternoon

A chance of showers & thunderstorms.  Local downpours.  Winds SW-W at 5-10 mph, with some higher gusts.  Temps varying from 60s upper elevations to the lower-middle 70s.

Wednesday Night Into Thursday Morning

A chance of showers & thunderstorms.  Local downpours possible.  Winds SW-WNW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temperatures mostly in the 50s.

Thursday Afternoon

Partly to mostly cloudy.  Chance of a hit-miss shower or thunderstorm, especially along and south of the High Knob Massif and Tennessee Valley Divide.  Winds W-WNW at 5-10 mph with higher gusts.  Temperatures varying from 60s at upper elevations to the mid-upper 70s.

Thursday Night Into Friday Morning

Partly to mostly cloudy.  Winds becoming light.  Seasonally cool with temperatures varying from 40s to lower 50s in the colder mountain valleys to the middle-upper 50s.  Areas of fog at lower elevations.

*More humid air will feature numerous showers and downpours in thunderstorms during Saturday and Sunday ( June 3-4 ).  Some of the thunderstorms could become strong to locally severe.

Weather Discussion ( SOS Into June )

Although any dry hours this week will be enjoyed, along with brief reductions in humidity, a return of more humid conditions into this weekend means that showers and downpours in thunderstorms will also be roaming the mountain landscape.

Spring 2017 has been wet across the region, with the second month in a row producing a general 8.00″ to 10.00″ of rain within the High Knob Massif ( after 5.00-7.00″ in March ).

May 1-30 Rainfall Totals

City of Norton
7.88″

Clintwood 1 W
8.49″

*Big Cherry Dam
10.05″

*The past 6 months have generated a general 47.00″ to 56.00″ of total precipitation in the High Knob Massif area ( around 52.00″ estimated on average at upper elevations ).  This translates to a general 8.00″ to 9.00″+ per month for the past six months.

There are some model signs that a more prolonged break in this very wet pattern could occur but, and this is a big but, such a break remains uncertain.  It might actually become more likely if a tropical or a tropical-like system develops far to the south and tracks across Florida and off into the western Atlantic Ocean.

Such a track could ideally place the Mountain Empire under a subsidence, or sinking air, regime around the periphery of the system ( especially if it were to strengthen a little ).

A break is uncertain since the European Ensemble MEAN  continues to show a tendency toward showers & storms along and just west of the Appalachians through the next couple of weeks.

The latest European Model is going with a synoptic-scale sinking air regime centered over Canada, but not along the Appalachians.

Perhaps the biggest factor, as often is the case at this time of year, is soil moisture with significant evapotranspiration to supply latent energy for formation of more showers and thunderstorms.  A wet feedback can be hard to overcome at this time of year, and would likely require a synoptic-scale forcing mechanism ( to generate significant subsidence ).

Mountain Area Forecast ( May 28-30 )

ALERT For High Water Levels And Flooding In Low-lying Locations Along The South Fork of the Powell River and Big Stony Creek of the Clinch River

More than 3.00″ of rain fell over the Big Cherry Lake basin and adjacent locations into Saturday evening ( May 27 ).  ROARING water and dangerously high levels will continue into Sunday.

The Storm Prediction Center Has Issued A Marginal Risk For Severe Thunderstorm Development Sunday

Thunderstorm development Sunday will largely be dependent upon cloud coverage and if the stabilizing overnight atmosphere can recover ( become unstable ) during the day.

*Downpours Of Flooding Rain Will Remain Possible Throughout The Memorial Day Holiday Period

Due to a super-saturated surface layer, and high rates of evapo-transpiration ( a positive moisture feedback ), showers and any thunderstorms which develop will remain capable of producing heavy rainfall and possible localized flooding.  

Overnight Into Sunday Morning

Low clouds.  Areas of fog.  A chance of showers.  Thunder possible.  Winds SW at 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temperatures from mid-upper 50s to the lower 60s.

Sunday Afternoon

Mostly cloudy.  A chance of showers and thunderstorms.  Any storm could become strong-severe.  Local downpours.  SW winds 5-10 mph, with higher gusts.  Temperatures in the 60s to lower 70s.  Dense fog possible at upper elevations ( i.e., orographic clouds ).

Sunday Night Into Memorial Day Morning

Mostly cloudy.  A chance of showers and thunderstorms.  Local downpours possible.  SW-W winds 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temperatures in the 50s to lower-mid 60s ( coolest at the highest elevations ).  Dense fog in upper elevations, with areas of fog at middle-lower elevations.

Memorial Day Afternoon

Mostly cloudy.  A chance of showers and thunderstorms.  Local downpours possible.  SW-WSW winds generally less than 10 mph.  Temperatures varying from 60s in upper elevations to the lower-middle 70s.

Monday Night Into Tuesday Morning

Mostly cloudy.  A chance of showers.  Thunder possible.  SW-W winds 5-10 mph, with higher gusts, along middle to upper elevation mountain ridges-plateaus.  Temperatures varying from 50s to middle 60s ( coolest at highest elevations ).

Weather Discussion ( Saturated )

The mountain landscape is not only saturated, it is super-saturated, in wake of a wet Spring 2017 and torrential rain producing thunderstorms on Saturday ( May 27 ).

Cumulonimbus clouds & orographic mountain waves, as well as low-level orographic clouds ( across Little Stone Mountain Gap and the Powell Valley Overlook area as seen at lower right of below image ), formed as severe thunderstorms with flooding rains, damaging winds, and vivid lightning developed Saturday afternoon-evening.

Rapid convective development occurred during the mid-late afternoon hours of Saturday, with overshooting cloud tops and gravity waves, indicative of vigorous upward motion, clearly seen on new GOES-EAST Imagery ( below ).

Although the amount of convective formation is uncertain during Sunday, the situation is now so saturated that a wet feedback for rain shower development means that it will take little upward motion to trigger new activity ( i.e., even showers without thunder will be capable of downpours ).

Any breaks within the overcast will make showers-storms nearly certain to develop amid this “jungle-like” setting.

It is hoped that Memorial Day afternoon will be dry, but for now I have left a chance of showers-storms in the forecast until it is seen if somewhat drier low-level air can actually reach the Cumberland Mountains ( stay tuned for updates ).

The continuation of mean upper air troughing + wet ground means that this unsettled pattern will continue into early June, with dry periods to be savored in between showers and thunderstorms.

While generally humid, the cooler than average temp regime observed since May 21 will also continue.

Although this pattern can certainly change, wet ground and abundant evaporation + transpiration heading into summer often develops a feedback that helps to maintain a setting which is unsettled via input of abundant moisture into the atmosphere ( latent heat energy for storm formation ).

*Positive and negative feedbacks are an important part of every summer season and are driven largely by soil-vegetative moisture inputs ( or the lack thereof ) into the overlying air.  Seasons with abundant moisture input into the lower atmosphere often trend wetter and cooler than average versus those which feature dry ground and reduced evapotranspiration ( ** ).

**Cooler by day, especially, since drier summer seasons in the mountains can feature anomalous nocturnal coldness at times ( with frost-freezing temperatures having been observed during every month of the year amid high mountain valleys, sometimes this may be due to low dewpoint air behind strong summer fronts…but in seasons like Summer 1988 it was largely due to developing drought conditions ).

Mountain Area Forecast ( May 26-28 )

Severe Thunderstorms Will Impact The Area Saturday Evening & Night – With Severe Thunderstorm Watches And Warnings Likely.  Stay Tuned To NOAA Weather Radio And Favorite Media Sources.

The Storm Prediction Center Has Issued A Slight Risk Of Severe Thunderstorm Development For Saturday Into Sunday ( May 27-28 )

A Potential Derecho, Impacting Areas From Missouri Across Kentucky and Tennessee, Will Become A Major Weather Force Into Saturday Night And Early Sunday As It Moves Toward The Appalachians

**A Risk Of Flooding Rainfall Will Exist Throughout The Memorial Day Holiday Weekend

Overnight Into Friday Morning

Rain showers and areas of drizzle, ending overnight into morning.  Low clouds.  Areas of dense fog ( widespread at upper elevations then cloud bases lifting into morning ).  Winds WSW-W at 5-15 mph, with higher gusts, on ridges and plateaus below 2700 feet.  Winds W-WNW 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures widespread in the 50s, except near steady or slowing rising to around 50 degrees on highest ridges.

Friday Afternoon

Partly cloudy with increasing high clouds by late.  Warmer.  Winds W-SW 5 to 15 mph with higher gusts.  Temperatures varying from 60s in upper elevations to the mid-upper 70s.

Friday Night Into Saturday Morning

Partly to mostly cloudy ( high clouds ).  Areas of dense valley fog.  Winds SSW-WSW at 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges. Temperatures varying from mid-upper 40s to lower 50s within cooler mountain valleys to the lower-middle 60s.

Saturday Afternoon

A chance of showers & downpours in thunderstorms.  Some storms could be strong to severe.  Humid.  Winds SW-WSW at 5-15 mph, with higher gusts.  Temperatures varying from upper 60s to lower 70s at highest elevations to upper 70s to lower 80s.

Saturday Night Into Sunday Morning

A chance of showers & downpours in thunderstorms.  Some storms could be strong to severe.  Humid & hazy.  Areas of fog possible.  Winds SW at 5 to 15 mph with higher gusts.  Temperatures widespread in the 60s.

Sunday Morning Into The Afternoon

A chance of showers & downpours in thunderstorms.  Some storms could be strong to severe.  Winds SW-W at 5-15 mph with higher gusts.  Temperatures varying from 60s within upper elevations to the lower-middle 70s.

Weather Discussion ( Stormy )

Early Overnight of Saturday Update

A beautiful ending to Friday was a nice way to kick off the Memorial Holiday Weekend.  Unfortunately, these pristine conditions will not last with increasingly humid & unstable air poised to build across the mountain landscape ( MCS ).

The Storm Prediction Center continues to be very aggressive with an outbreak of severe thunderstorms Saturday.  While some strong to severe thunderstorms may develop locally over the mountains as afternoon instability increases, the main concern by late Saturday & Saturday Night could be  formation of a Mesoscale Convective System ( MCS ).

The MCS develops initially over the Mississippi Valley then rolls eastward across Kentucky and Tennessee toward the Appalachians with a wind damage threat ( there is some potential for a long-lived wind damage producing MCS to form given the instability gradient that will be developing across the Mississippi and upper Tennessee valleys ).

That is the preliminary scenario.  Stay tuned for updates as the atmosphere responds to actual thunderstorm formation during Saturday ( with luck any such system will weaken by the time it reaches the mountains, but that can not yet be counted on so that everyone should remain alert and have ways to receive watches-warnings that will be issued ).

Previous Discussion

A stormy May 2017 weather pattern will continue through the Memorial Day Holiday period, with very unstable air developing over the mountain region as another frontal boundary stalls across the Mountain Empire.

*Temperatures in the 40s, with wind chills in the 30s, were observed throughout the daylight hours of Thursday at upper elevations in the High Knob Massif which were engulfed in orographic clouds ( dense fog ) and persistent rain showers.

Widespread 50s were observed at lower-middle elevations under an upper level low.  These conditions will change radically into this Memorial Day Holiday Weekend.

Given a saturated landscape this is not good news, with an enhanced risk for flooding rains due to a combination of antecedent conditions ( wet April-May ) and downpours within showers and thunderstorms.

Antecedent Conditions

Clintwood 1 W NWS

April 1 to May 25 Rainfall
6.76 + 7.61 = 14.37″

*April 1 to May 1-25 rainfall totals as great as 16.00″ to 18.00″ have been observed across the southern Appalachians, from western to eastern slope sites ( e.g., High Knob Massif, Grayson Highlands State Park, Grandfather Mountain ).

**Flooding rains in the Town of Clintwood during May 24 were caused by days of significant rainfall prior to the 0.63″ that officially fell into the rain gauge = the importance of antecedent conditions which allowed me to be able to forecast flooding rains before they developed.  The potential for more flooding will have to be respected through the Memorial Day Holiday Weekend.

While forecast models will struggle to pinpoint locations of heaviest rainfall, again the signal and atmospheric setting is clearly indicating showers & flooding downpours within thunderstorms, some of which may be strong-severe.

In addition to another high precipitable water air mass along an west-east stalling boundary, this returning air mass is also forecast to become very unstable.

An axis of very high Convective Available Potential Energy, called CAPE, will extend across much of Kentucky toward the western side of the Appalachians by later Saturday.

The Supercell Composite forecast, formed in part by the amount of cross-over which occurs vertically between the 850 MB and 500 MB levels, is also predicted to reach rather significant values.

These risk regions may be altered as the time for this event gets closer, as well as extended through the remainder of this Holiday Weekend ( check back for updates ).

A plume of rich moisture, with elevated values of 925 MB theta-e ( equivalent potential temperature ) possesses a subtropical connection from the Gulf of Mexico and will continue the potential for flooding rains throughout the Memorial Day Holiday period.

A developing jet streak in upper level wind fields by late in the weekend and Memorial Day will need to be followed for enhancement of showers-thunderstorms over the southern Appalachians and Tennessee Valley.

These parameters, and many more, will need to be closely followed by forecaster’s heading into this weekend.  Stay tuned to NOAA Weather Radio and your favorite media sources for watches and/or warnings which will likely be needed.

Mountain Area Forecast ( May 22-25 )

The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development During Wednesday & Wednesday Night

Waves of showers and downpours in thunderstorms will be observed through Thursday.  Some thunderstorms could be strong to locally severe Wednesday afternoon-evening as colder air begins moving in aloft and a low-level jet forms.  

Damaging winds, hail, and flooding rains are the main dangers Wednesday ( lightning is always a danger ).

*A total of 1.35″ of rain was measured in Clintwood during the 24-hour period ending at 7:00 AM Wednesday.  Streams are running high in locations having significant rains during recent days. 

Remain alert to NOAA Weather Radio and favorite media sources for possible watches and/or warnings that may be issued with this system.

Strong & gusty winds will usher in very chilly air Thursday, with orographic rainfall enhancement possible.  Air temps will drop into the lower-mid 40s at the summit level of the High Knob Massif by Thursday AM, and struggle in the 40s during the day amid dense fog and wind chills in the 30s.  Conditions at middle & lower elevations, below 3000 feet, will also be unseasonably chilly with widespread 50s and wind chills in the upper 30s to middle 40s within locations along and north of the Tennessee Valley Divide.

Overnight Into Monday Morning

A chance of showers and thunderstorms.  Local downpours possible.  Areas of dense fog, widespread upper elevations.  S-SW winds shifting WNW to NNW by morning at 5-15 mph, with higher gusts, on middle to upper elevation mountain ridges.  Temperatures varying from the lower 50s to lower 60s ( coolest at the highest elevations ).

Monday Afternoon

Partly cloudy and less humid.  NW to N winds mostly less than 10 mph.  Temps varying from low-mid 60s in upper elevations to the lower-middle 70s.

Monday Night Into Tuesday Morning

Becoming cloudy.  A chance of rain and showers developing by the predawn-morning hours. Light winds.  Temperatures varying from upper 40s to low 50s within cooler mountain valleys, and highest mountain ridges, to the middle-upper 50s.  Areas of fog.

Tuesday Afternoon

Mostly cloudy. A chance of showers & thunderstorms.  Local downpours.  Light SE-S winds.  Temperatures varying from 50s within upper elevations to the middle-upper 60s.

Tuesday Night Into Wednesday Morning

Showers & thunderstorms becoming likely.  Downpours possible.  Winds SE-S at 5-10 mph, with some higher gusts, along mid-upper elevation mountain ridges-plateaus. Fog widespread in upper elevations ( dense ), with areas of fog at other elevations.  Temperatures in the 50s to low 60s.

Wednesday Morning Through The Afternoon

Showers & thunderstorms.  Downpours of heavy rain with local high water issues possible.  Areas of fog, widespread upper elevations in the High Knob Massif.  SE-S winds 5 to 15 mph, with higher gusts, shifting SSW.  Temperatures widespread in the 50s to middle-upper 60s.

Wednesday Night Into Thursday Morning

Periods of showers.  Thunder possible.  Downpours possible.  Winds shifting SSW-SW and increasing to 10-20 mph, with higher gusts.  Temperatures falling into the low-mid 40s to the lower-middle 50s ( coldest at highest elevations ).  Fog widespread and dense at upper elevations.  Wind chills in the 30s and 40s ( coldest at highest elevations ).

Thursday Afternoon

Unseasonably cool with low clouds, fog, and periods of rain and showers.  SW to W winds 10-25 mph, with higher gusts.  Locally heavy rainfall.  Temperatures varying from 40s at upper elevations to the 50s in Norton-Wise.  Colder wind chills, especially on mid-upper elevation ridges-plateaus.

A cool air mass is expected to rule the mountain landscape during Thursday into Friday ( May 25 to 26 ).  MAX temperatures in upper elevations will struggle to break out of the 40s on Thursday, with 50s to around 60 degrees at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide.

Weather Discussion ( Wet Spring )

Monday Afternoon Update ( May 22 )

A general model trend toward the European Ensemble Mean has resulted in my update to increase rainfall, and chances of rainfall, during Tuesday into Wednesday for locations in the Cumberland Mountains ( with more rain into Thursday ).

Monday afternoon temperatures varied from upper 50s to lower 60s at upper elevations in the High Knob Massif to the upper 60s to lower 70s ( 69 degree MAX in Clintwood and 68 degrees in Wise ).

A wetter and cooler than average week ( much cooler than average by Thursday ) is expected to rule the domain of the southern Appalachians.

Models struggle with specific rainfall amounts at this time of year, therefore the general pattern is more important to look at versus any given point forecast of amounts.

Previous Discussion

Spring 2017 has been wet across the Mountain Empire, with more rain upcoming this week.  How much rain; however, is the question as recent model trends have shifted the axis of heavy rains eastward to along and east of the Blue Ridge.

*Widespread rain and generally cool temperatures helped to reduce the convective rainfall potential across the Cumberland Mountains during Sunday ( May 21 ).  MAX temperatures varied from 50s in upper elevations of the High Knob Massif to 60s at middle-lower elevations ( a MAX of 67 degrees in Clintwood ).

Latest runs of the NAM and GFS models are in pretty good agreement with the axis of heaviest rains developing along and east of the Blue Ridge.  The 12z Sunday European Model Ensemble MEAN is a little farther west with the rains.  So possible adjustment could be needed in the local forecast for Tuesday-Wednesday.

This marks the beginning of a cooler than average week for this time of year, with the coolest conditions expected by Thursday-Friday ( May 25-26 ).

Cooler than average conditions are expected this week from the southern Appalachians west and northwest across the central & northern Plains ( along and east of the Rockies ).

MIN temperatures in the 30s will be possible in high mountain valleys, at least, of the High Knob Massif by later this week.

Mountain Area Forecast ( May 18-21 )

ALERT For Showers & Thunderstorms With A Heavy Rainfall Potential Into Sunday And Sunday Night 

A high water content air mass will set the stage for heavy rainfall as a upper air trough & surface cold front approach the mountains Sunday.  Remain alert for strong rises along streams and for possible high water issues.  Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings which may be needed.

The Storm Prediction Center Has Issued A Marginal Risk Of Severe Thunderstorms Into Sunday Morning

( Former Alerts )

The Storm Prediction Center Has Issued A Marginal Risk Of Severe Thunderstorm Development During Friday And Friday Night

Tonight Into Friday Morning

Partly cloudy.  A chance of showers & thunderstorms by overnight into morning.  Downpours possible.  Winds SSW to WSW 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges and plateaus.  Mild with temps dropping into the 50s ( coolest valleys ) to middle 60s.

Friday Morning Through The Afternoon

A chance of showers & downpours in thunderstorms.  Some storms could be strong to locally severe.  Winds SSW-WSW at 5-15 mph with some higher gusts.  Temperatures varying from the 60s to mid-upper 70s ( coolest highest elevations ).

Friday Night Into Saturday Morning

Partly-mostly cloudy.  Areas of fog.  Chance of a hit-miss shower or thunderstorm.  Light winds.  Temperatures from the 50s to lower-middle 60s ( coolest in mountain valleys ).

Saturday Afternoon

Partly sunny.  Unseasonably warm with a chance for hit-miss showers or thunderstorms.  Local downpours possible.  SSE-S winds at 5-10 mph with higher gusts.  Temps varying from 70s in the upper elevations to the mid-upper 80s.

Saturday Night Into Sunday Morning

Partly cloudy.  A chance of showers and downpours in thunderstorms, especially toward morning.  Winds SSE-SSW 5-15 mph, with higher gusts.  Temperatures varying from the upper 50s to lower-middle 60s.

Sunday Morning Through Sunday Afternoon

Periods of showers & downpours in thunderstorms.  Humid.  Winds SSE-SW at 5-15 mph, with higher gusts, along middle to upper elevation mountain ridges, shifting toward the W-WNW by evening.  Areas of fog, widespread across upper elevations.  Temps varying from the 60s to the lower 70s.

Weather Discussion ( Pattern Change )

Mesoscale Discussion – Saturday Evening

Hit-miss storms into Saturday have been productive rain producers, and this trend will continue as the conditions for more widespread activity increases into Sunday ( a total of 1.56″ of rainfall was measured in Clintwood during the 24-hour period ending at 7:00 AM Saturday ).

*As observed Saturday, a severe component has also been present with thunderstorms that form locally.  Although the potential for severe thunderstorms will diminish into Sunday, a locally strong or severe thunderstorm can not be ruled out ( especially by later in the day as drier mid-level air approaches from the west ).

Moisture advection ( transport ) tonight into early Sunday will generate a deep, saturated vertical profile.

Precipitable water values approaching 2.00″ will occur into the day Sunday ( i.e., essentially the amount of water in a vertical column of air that could fall out over a single spot; however, orographics and storm circulations can work to concentrate air locally to generate much higher values ).

A strong cyclone lifting northeast into the upper Midwest will be tapping tropical moisture, as denoted by the theta-e ( potential temperature ) forecasts for Sunday.

Even as mid-level moisture begins to decrease a rich plume of low-level moisture ( high 925 MB theta-e values ) will continue to feed into the area along a frontal boundary.

*In mountainous terrain high values of low-level theta-e air are very important, since this is the air that is lifted by topographic features to help enhance precipitation production.

Folks living along streams and in flood prone, low-lying areas will need to remain alert through Sunday for the possibility of rapid water rises.

*Only a brief break is now expected Monday before moisture values increase again into Tuesday-Wednesday to generate more rounds of significant rains.

Saturday ( Overnight ) Discussion

Thunderstorms with locally heavy rain developed during the overnight-early morning hours of Friday.

Some of the heaviest rain fell across Scott County into portions of the High Knob Massif ( 0.75-1.00″ or more fell from Maple Gap into Big Cherry Lake basin, and from Natural Tunnel State Park across adjacent communities from Jasper & Duffield to Gate City ).

A humid but less “hot” Friday followed with MAX temperatures varying from 60s in upper elevations of the High Knob Massif to the middle-upper 70s ( 74 degrees in Clintwood ).

Another round of strong thunderstorms moved southeast from Kentucky across portions of southwestern Virginia into early overnight hours of Saturday.

While the placement of heaviest rains vary depending upon the model used, the atmospheric setting is clearly one that supports heavy to locally excessive rain.

Although many dry hours are expected through Saturday, wet ground will combine with moisture transport ahead of a slow moving upper trough and front to set the stage for thunderstorms with heavy rainfall into Sunday.

Previous Discussion

A stormy and eventually cooler trend is being highlighted as another pattern flip across the USA produces a notable change into next week.

A few hit or miss showers and thunderstorms, along and northwest of the Virginia-Kentucky stateline, Thursday will give way to a renewed chance for thunderstorms overnight into Friday as a weak disturbance crosses the mountains.

Many dry hours follow ( for places that get hit Friday ) into this weekend before shower-thunderstorm chances ramp up by later Sunday into Monday ( May 21-22 ).  This occurs ahead of large-scale ( synoptic ) changes that will push the pattern back into a cooler and wetter regime.

*A downsloping SSE-S air flow across southwestern Virginia and the eastern portions of Tennessee will tend to reduce chances of showers-thunderstorms during much of this weekend until air flow trajectories begin changing by later Sunday into Monday,  with an upward spike in precipitable water values.

Another unseasonably warm day will occur under this general downsloping pattern during Saturday, with only a chance for localized hit-miss showers-storms triggered by instability and major terrain features. 

A major transition from upper ridging and anomalous warmth to upper troughing and anomalously cool air is being forecast by the ensembles.  This change is looking currently to dominate much of next week.

A heavy rain-thunderstorm potential initially arises during the transition from later Sunday into Monday ( May 21-22 ).

Additional disturbances and unseasonably cool air aloft will then contribute to a wetter than average pattern under the mean upper trough, with European Model Ensemble MEAN basin average rainfall totals of 3.00″ to 5.00″ along the Appalachians through the remaining days of May.

*A similar scenario is currently being shown by the GFS Model Ensemble MEAN.  Confidence in this pattern flip is higher than average, with daily details ( with respect to clouds & chances of showers and thunderstorms ) to be worked out into next week.

Mountain Area Forecast ( May 15-17 )

Overnight Into Monday Morning

Mostly clear.  Areas of dense river valley fog.  Large vertical temperature spread between colder mountain valleys and milder ridges-plateaus.  Winds SW-WNW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges and exposed plateaus.  Temperatures varying from lower-middle 40s in colder mountain valleys to mid-upper 50s.

Monday Afternoon

Partly to mostly sunny.  Winds NW-N at mostly less than 10 mph.  Temperatures varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s.

Monday Night Into Tuesday Morning

Mostly clear.  Large vertical temperature spread between colder mountain valleys and milder ridges.  Light winds.  Temperatures varying from 40 to 45 degrees in the colder mountain valleys to mid-upper 50s.  Areas of dense river valley fog ( widespread along the Clinch & Cumberland ).

Tuesday Afternoon

Partly to mostly sunny.  Unseasonably warm.  Winds SW at 5-10 mph, with some higher gusts.  Temperatures varying from 70s in upper elevations to the middle-upper 80s.

Tuesday Night Into Wednesday Morning

Partly cloudy during the evening with increasing high clouds overnight into morning.  S-SW winds 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges.  Temperatures varying from 50s in cooler valleys to the 60s along exposed mountain ridges-plateaus.

An increasing chance for hit-miss showers and thunderstorms will be observed during late week into the upcoming weekend.  Heavy rainfall will be possible by this weekend into next week ( note that any thunderstorm at this time of year can cause heavy local rain ).  Stay tuned for later forecast updates on this potential.

Weather Discussion ( Warmer )

Although chilly nights will continue for a couple more days in mountain valleys, the pattern is shifting toward much warmer and gradually more humid conditions.  Eventually, by later this week into the upcoming weekend, this will set the stage for showers and downpours in thunderstorms.

Temperatures into Mother’s Day morning dipped into the lower 40s in Clintwood and Norton and well down into the frosty 30s within high mountain valleys in the High Knob Massif ( other locations with 30s included Burkes Garden and Shady Valley ).

Large temperature differences between chilly mountain valleys and milder ridges & exposed plateaus will continue during morning hours of Monday and Tuesday mornings.

Within complex mountain terrain surface dewpoints in valleys with access to the higher terrain are not that important during conditions favorable for drainage.

*Dewpoints and the cooling potential of air at the top of drainage basins are more important under this type of condition.  That is why nocturnal temperatures can drop below dewpoints observed in lower-middle elevation valleys, and how high wetland valleys that may quickly reach near 100% RH can continue to cool during the night as lower dewpoint air aloft drains downward from high mountain ridges ( radiational cooling + lower dewpoint air = lower valley temps amid complex mountain terrain than often forecast ).

The time of year for widespread river valley fog is nearing, as folks living within the Clinch River Valley of Scott and Russell counties and the Powell River Valley, from East Stone Gap-Big Stone Gap into Lee County, know well.  The drainage of cool air downward out of the High Knob Massif and Tennessee Valley Divide working to enhance fog formations ( the latent heat that releases with condensation adds warming to the air, countering some of the cooling to make these river valleys milder than their cold air drainage sources** ).  A similar setting being applicable to the Cumberland and Russell Fork-Levisa Fork river valleys. 

**There also appears to be a compressional warming factor after air vertically drops 1500 to 2000+ feet, even with drainage flows, as noted by valleys beneath the Black mountains in southeastern Kentucky which tend to be significantly milder than those on the Virginia side.  More will be learned as a University Of Virginia’s College At Wise microclimatology field research project continues through coming seasons and years. 

Like water, which gushes out of the high country, air drains into upper elevation valleys ( where it chills most ) and then continues downward through middle into lower elevations under the continuous force of gravity when conditions are favorable for nocturnal temperature inversions and development of cold air drainage flows.

While a digging western USA upper trough will pump up or raise heights across the eastern USA ( warming air expands such that the height of any given isobaric surface is raised upward in the atmosphere ) during the next 5 days, a trend toward an eastward shift of storminess within the “clash” zone between the western trough-eastern ridge will occur.

Hit or miss afternoon showers and thunderstorms will initially become possible due to daytime heating and the increase of instability; however, by this weekend into next week ( especially ) it appears that more widespread and organized showers-thunderstorms will become likely.

At this time of year, as already observed this month, the positioning and potential stalling of any frontal zone will have to be monitored closely.

Check back later this week for a better idea of timing on any potential heavy rainfall setting that may be upcoming.

Mountain Area Forecast ( May 11-14 )

Current Alerts

ALERT For Ponding Of Water Along Roadways And For Dense Fog Development Into Middle Elevations Along And North Of The High Knob Massif Into Saturday AM

Run-off from moderate-heavy Friday rainfall has caused ponding of water along roadways.  Slow down and be extra careful.  In addition, low cloud bases are currently causing widespread dense fog at elevations above 2900 feet.  Expect lowering of cloud bases overnight into Saturday Morning, to around or locally below the elevation of Wise, on rising northerly air flow along & north of the High Knob Massif.

Former Alerts:

The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development Thursday PM Through Thursday Night

Wind damage will be the primary threat with any strong to severe thunderstorms Thursday Afternoon & Thursday Night.  Otherwise, heavy rainfall will be a concern from Thursday Evening Through Friday Night.  Folks living and/or driving through low lying and flood prone locations should remain alert for ponding of water and strong rises on streams.  Never drive through a flooded road, TURN AROUND and DO NOT DROWN.

While a Flash Flood Watch is officially in effect through Friday for Dickenson and Buchanan counties, adjacent locations across Wise, Scott, Lee, and Russell counties will also be at risk for strong rises on creeks and rivers.

Stay tuned to NOAA Weather Radio and your favorite media sources for possible warnings and additional watches that may be needed through Friday.

Remainder Of Thursday Afternoon

Partly-mostly cloudy.  Chance of showers & thunderstorms, especially in portions of Dickenson and Buchanan counties.  Gusty.  SW-WNW winds at 10 to 20 mph, with higher gusts.  Temperatures varying from 60s in upper elevations of the High Knob Massif to the upper 70s to lower 80s.

Thursday Evening Through Friday Morning

Showers & thunderstorms becoming likely.  Some storms could be strong to locally severe.  Downpours of heavy rain.  Winds becoming SSE-SSW and diminishing overnight into morning.  Areas of dense fog.  Unseasonably warm with temperatures widespread in the 50s to around 60 degrees.

Mid-Morning Friday Through Friday Afternoon

Showers & thunderstorms.  Locally heavy rainfall possible.  Light and variable winds becoming northerly.  Low clouds with widespread dense fog in upper elevations ( orographic cap clouds ).  Temperatures varying from 50s at the upper elevations to the 60s within middle and lower elevations.

*Lowering cloud bases and dense fog will become a factor at middle to upper elevations during Friday Night into Saturday AM, with the potential for cloud bases to drop downward across the Wise & Sandy Ridge plateaus ( to around or below 2500 feet ) on upsloping northerly air flow toward the High Knob Massif.

Friday Night Into Saturday Morning

Showers to drizzle.  Turning chilly.  Low clouds with dense fog from around the elevation of Wise upward in elevation.  Winds NNW to NNE at 5-15 mph, with higher gusts.  Temps dropping into 40s to around 50 degrees ( near 40 degrees at summit levels of the High Knob Massif ).  Wind chill factors in 30s and 40s ( coldest at highest elevations ).

Saturday Morning Through The Afternoon

Low clouds-fog-drizzle during the morning ( especially at higher elevations ) giving way to partly-mostly sunny skies during the afternoon.  Winds NW-N at 5-10 mph with higher gusts.  Temperatures varying from the lower-middle 50s in upper elevations to the 60s ( warmer to the south within lower elevations of the Great Valley ).

Saturday Night Into Sunday Morning

Large vertical temperature spread developing between colder valleys and exposed mountain ridges & plateaus.  Mostly clear evening skies, then increasing clouds possible overnight into morning.  Winds becoming WSW to WNW at 5 to 15 mph, with higher gusts, along exposed middle-upper elevation mountain ridges.  Generally light valley winds.  Temps varying from 30s to lower 40s in mountain valleys to the upper 40s to low-mid 50s.

Weather Discussion ( Changeable )

Changeable is probably the best way to describe weather conditions through upcoming days, with the first order of business being a developing cluster of thunderstorms that will move across the mountains Thursday evening.

Although temperatures are mostly in the 60s ( upper elevations ) and 70s ( middle elevations ) to lower 80s ( lower elevations and or places under downsloping air flow ), there is a notable haze and increase in low-level moisture in advance of developing thunder-storms upstream of the mountains.

A few storms currently have warnings on them in Kentucky and this will be a trend to watch through the remainder of this afternoon into this Thursday evening as a cluster of thunderstorms ( MCS or Mesoscale Convective System ) comes together over the foothills and mountains.

Cloud tops are growing vertically and expanding upstream, and while a wind damage potential does exist the threat for heavy rainfall will certainly be a concern with more rounds of showers-thunderstorms expected Friday.

With convection it is always difficult to pinpoint places receiving heaviest rain amounts, but the signal is clear.

Locally heavy rainfall amounts are likely through Friday.

Following a cooling trend behind all this mess into this weekend, with chilly temperatures in mountain valleys being notable Saturday evening into Mother’s Day morn, major warming will become the theme next week.

A big trough developing over the western USA will pump up heights across the eastern states and generate anomalously warm conditions for a good portion of next week.

*Nights may continue to be cool in mountain valleys if winds are light, but days are clearly trending toward being unseasonably warm for this time of year during next week.

Mountain Area Forecast ( May 8-10 )

A Heavy Rainfall And Thundestorm Cluster Setup Is Being Monitored For Thursday Night Through Friday Night Into Saturday Morning.

Former ALERTS:

ALERT For Frost & Freezing Conditions In Colder Mountain Valleys Into Monday Morning

Low temperatures will drop into the 30s within many mountain valleys overnight into Monday morning, with upper 30s to lower 40s on exposed middle-upper elevation mountain ridges-plateaus.  The coldest mountain valleys will drop into the 20s to lower 30s, mainly at elevations above 2000 to 3000 feet.

Overnight Into Monday Morning

Becoming clear.  Chilly.  NW winds 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges.  Light valley winds.  Areas of frost, most widespread in the colder, sheltered valleys.  Temperatures varying from 20s to lower 30s in colder valleys ( at mid-upper elevations ) to the upper 30s to lower 40s ( exposed mountain ridges ).

Monday Afternoon

Mostly sunny ( beautiful blue skies ).  Milder.  WNW to NW winds 5-15 mph, with higher gusts.  Temperatures varying from 50s in upper elevations to the lower-middle 60s.

Monday Night Into Tuesday Morning

Partly to mostly clear during the evening, then increasing clouds with a chance of showers-thunderstorms overnight into morning.  Rapid evening temp drop in valleys before rising overnight.  NW-W winds 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges.  Temperatures varying from 30s to lower 40s in coldest valleys ( before rising ) to the 40s to lower 50s.

Tuesday Afternoon

Partly to mostly cloudy.  Warmer  A chance of showers and thunderstorms.  Winds WSW to WNW at 10-20 mph, with higher gusts.  Temps varying from the 60s to lower 70s.

Tuesday Night Into Wednesday

Partly to mostly cloudy.  Mild.  A chance of showers and thunderstorms.  Winds WSW-WNW at 10-20 mph, with higher gusts on mid-upper elevation mountain ridges- plateaus.  Temperatures widespread in the 50s to lower-middle 60s.

Wednesday Afternoon

Partly cloudy.  Warm.  A slight chance of a hit-miss shower or thunderstorm.  Winds SW-WNW at 5-15 mph, with higher gusts.  Temperatures varying from upper 60s to lower 70s at highest elevations to the upper 70s to lower 80s.

Weather Discussion ( Unsettled )

Monday Evening Update

A frosty morning greeted colder mountain valleys with low temperatures varying from the upper 20s to the middle 30s.

The low temperature reached 34 degrees in Clintwood.

The coldest low temperature recorded in the area occurred within high valleys of the High Knob Massif, where colder valleys dropped into the upper 20s.  The time spent below freezing was limited by abundant clouds into the early overnight, followed by strong predawn temperature drops.

The MEAN low temperature observed at the Big Cherry Wetland Valley 4 site has been 38.4 degrees so far during the month of May.

Previous Discussion

A chilly weekend was observed across the mountains with snow pouring down at the summit level of the High Knob Massif during Saturday.  Although generally not sticking, with temps around or above freezing at 4200 feet, such was not the case upon climbing upward in elevation to the very highest summits where up to 7″ of snow depth accumulated on top of Mount LeConte in the Smokies.

Wind chills dropped into the 10s atop the High Knob Massif to put a true wintry feel into the air.  Clearing skies by Sunday morning allowed air temperatures to reach the 20s to around 30 degrees.

A milder but gusty Sunday afternoon graced the mountain landscape beneath fair weather cumulus clouds.  This sets the stage for a cold night in mountain valleys as winds decrease overnight into morning.

Frost and freezing conditions will occur in colder locations versus a frost-free environment across exposed mid-upper elevations and the warmer valleys.  If you are uncertain about your location, it would be best to bring any tender plants not already in the ground inside for the night.

The focus then shifts toward a band of showers and thunderstorms that will be developing amid isentropic lifting along and northeast of a warm frontal zone by Tuesday into Wednesday.  The European Model group forecasts the heaviest rainfall corridor to set up from southern Ohio across central-southern West Virginia, northeast of the higher mountain terrain of the famed Mountain Empire.  Climatologically, this is favored but until it actually develops the exact corridor for heavy rainfall and thunderstorms can not be certain.  Thus, a heavy rainfall and thunderstorm cluster setup is being monitored ( as noted in my headlines at the top ).

In general the pattern will be unsettled and cooler than average for this time of year, especially from late week into early next week.  The 51-Member European Ensemble MEAN is forecasting a general 2.00″ to 5.00″ of rainfall along the southern-central Appalachians during the next couple of weeks ( through the middle week of May ).  Since this is “basin-average” rainfall amounts, during the convective season this means the potential for locally higher totals will have to be respected.

Mountain Area Forecast ( May 5-7 )

An Alert For Frost & Freezing Conditions May Be Needed Across Much Of The Area By Monday Morning

*Temperatures around or below freezing will be possible on highest peaks into Saturday morning, and in high valleys and peaks on Sunday morning.

Overnight Into Friday Morning

Showers with a chance of thunder.  Winds shifting SW to WNW at 5 to 15 mph, with higher gusts.  Temperatures dropping into low-mid 40s at highest elevations to the upper 40s to mid 50s.  Low clouds ( dense fog ) in upper elevations.

Friday Afternoon

Showers.  Low clouds & chilly.  Winds SSW-W at 5-15 mph, with higher gusts.  Temperatures rising very little or slowly falling in the 40s ( upper elevations ) and middle 50s to lower 60s at middle-lower elevations by late afternoon.

Friday Night Into Saturday Morning

Rain & showers.  Turning colder.  Rain becoming mixed with or turning to snow at elevations above 3500 feet overnight into morning.  WNW to NW winds 10-20 mph, with higher gusts.  Temperatures varying from around freezing at highest elevations to low-mid 40s.  Wind chill factors within the 20s and 30s, except 10s in gusts on highest summits ( above 3600 feet ).  Orographic clouds-dense fog upper elevations ( becoming freezing fog highest peaks ).

Saturday Mid-Morning To Mid-Day

A break possible in showers.  Partly to mostly cloudy.  Winds WNW-NW 5-15 mph, with higher gusts.  Temps in the 30s ( upper elevations ) to the 40s ( low-middle elevations ).

Saturday Afternoon

Low clouds.  Showers redeveloping.  Rain and/or snow mix on highest peaks.  Local small hail possible.  Winds WNW-NW at 10-20 mph, with higher gusts.  Temps varying from 30s in  upper elevations to middle 40s to lower 50s. Dense fog at upper elevations.  Wind chills varying from 20s in upper elevations to the 30s to around 40 degrees.

Saturday Night Into Sunday Morning

Low clouds.  Showers tapering to drizzle before ending.  Clearing possible by morning.  Cold.  Winds W-NW at 5-15 mph, with some higher gusts.  Temperatures varying from 20s to around 30 degrees on highest peaks and high valleys to the upper 30s to around 40 degrees.  Wind chills varying from 10s & 20s at highest elevations to the 30s.  Dense fog in upper elevations ( freezing fog highest peaks ) giving way to clearing toward morning.

Sunday Afternoon

Mostly sunny (  deep blue ) skies.  Gusty & chilly.  Winds WNW-NW at 10-20 mph, with higher gusts.  Temperatures varying from low-mid 40s at highest elevations to the middle-upper 50s.  Wind chills in the 30s and 40s across middle-upper elevation mountain ridges.

Weather Discussion ( Chilly & Wet )

An unseasonably cold, for this time of year, pattern is taking shape for this weekend into much of next week.

Dramatic cloud formations, as often is the case when SE winds blow across the High Knob Massif, were on display throughout much of Thursday ( May 4 ).

A persistent standing wave on the SE flow stood for hour after hour as strong-gusty winds blew upward across the high country.  Although changing specific appearance at any given moment, the general cloud formation remained consistent through time.

While below freezing air and even flakes of snow are not uncommon during May, especially in the high country, the upcoming pattern is going to be unseasonably cool during the next 10 days ( in the mean ).

Temperatures in the 30s have occurred in high valleys within the High Knob Massif recently during morning hours of April 26 and May 3; however, temperatures in the 20s within high valleys will likely occur by early next week ( perhaps as early as Sunday AM if skies should clear before sunrise ).  This is a given.

The more critical forecast will be for lower-middle elevations, even the thermal zone orchard belt, where some frost sensitive crops may already be planted.  Stay tuned for updates.

The European Model group ensemble MEAN is showing  troughing across the eastern USA, with a general Omega Blocking feature that allows the pattern to reload next week just as it appears that warming might take hold.

This results in an unseasonably chilly May pattern.

If this forecast verifies, unseasonably cold air for this time of year will continue through the first half of May.  Timing when frost and freezing conditions occurs will be the main forecast challenge upcoming.

Mountain Area Forecast ( May 1-3 )

ALERT For Strong SSW-W Winds Through Monday

The Storm Prediction Center Has Issued A Risk For Severe Thunderstorm Development Monday

*An Enhanced Risk for Severe Thunderstorm Development will exist East to Northeast of the Cumberland Mountains, with the potential for upscale growth into a damaging squall line in locations along and east of the Blue Ridge.

Stay tuned to NOAA Weather Radio and your favorite media sources for any possible watches or warnings that may be issued during Monday.

Overnight Into Monday Morning

Mostly cloudy.  Windy & mild with a chance of showers.  SSE-SSW winds 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet.  Winds S-SW 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures widespread in the 60s.

Monday Morning Through Monday Afternoon

Showers & thunderstorms becoming likely.  Some storms could be strong to locally severe.  Windy.  SW to W winds at 15-25 mph, with higher gusts ( to 40+ mph ).  Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s.  Period of low clouds ( dense fog ) at the highest elevations.

Monday Night Into Tuesday Morning

Partly-mostly cloudy skies giving way to mostly clear conditions by morning.  Windy.  SW-W winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges and plateaus.  Temperatures varying from low 40s upper elevations to the upper 40s to lower 50 degrees.

Tuesday Afternoon

Partly to mostly sunny ( blue ) skies.  Cooler & windy.  WSW to W winds 10-20 mph, with higher gusts.  Temperatures varying from 50s in upper elevation to 60s to around 70 degrees at lower-middle elevations.

Tuesday Night Into Wednesday Morning

Mostly clear & chilly.  Winds shifting NW at 5-15 mph and decreasing toward morning on all but the highest mountain ridges.  Temperatures varying from 30s in upper elevations, and the coldest valleys, to the 40s.  Areas of river valley fog.

Weather Discussion ( Late Spring )

The arrival of May marks the final month of Meteorological Spring, and a shift into a cooler weather pattern in wake of unseasonable warmth during the second half of April.

April 2017 ended having produced a general 6.00″ to 10.00″ of rain along the Cumberland Mountains.

This wet pattern also looks to continue as temperatures chill downward during the first week or so of May.

The 51-Member European Ensemble MEAN is forecasting a upper air trough to dominate in the mean during the first 10 days of May, with basin average rainfall totals in the 3.00″ to 5.00″ range.

*Localized variations in amounts could be significantly greater, with both lesser and higher precipitation totals being possible during this period.

This results in a rather dramatic shift toward cooler than average temperatures for this time of year.

Much below average temperatures is currently being forecast during the May 4-10 period.

*Some model runs have actually shown the air cold enough for snow to fall at highest elevations along the central-southern Appalachians.  That remains to be seen, of course, but would certainly not be impossible ( i.e., it has occurred many times during past May’s ).