The Storm Prediction Center has issued a Marginal Risk for Severe Thunderstorm development during Tuesday Into Wednesday AM ( August 1 )
Storm Prediction Center Risk Regions
*Showers and downpours in thunderstorms will become likely into mid-late week. Heavy to locally excessive rainfall amounts will need to be closely monitored across the southern Appalachians.
Previous Headlines
*A drier and less humid air mass Saturday into early Sunday will give way to increasing moisture levels once again late Sunday into Monday ( July 30 ).
This will allow for cool nights, especially at upper elevations both Saturday and Sunday mornings, with a nice Saturday expected.
*Showers & downpours in thunderstorms will become likely next week with a locally heavy to excessive rain potential over the southern Appalachians and southeast USA.
Overnight Into Saturday Morning
Becoming clear. Cooler. Areas of dense fog, especially at middle to lower elevations. Winds NW-N 5-10 mph with higher gusts on mid-upper elevation mountain ridges into the overnight, then becoming light by morning. Temps from low-mid 50s at upper elevations to the upper 50s to around 60 degrees ( 40s possible in colder valleys at the upper elevations ).
Saturday Afternoon
Partly cloudy. Pleasant. Winds NW-NNE at generally less than 10 mph. Temperatures varying from 60s to lower 70s at upper elevations to 75-80 degrees.
Saturday Night Into Sunday Morning
Mostly clear ( some mid-high clouds ). Areas of dense fog in stream-river valleys ( especially at lower elevations ). Light easterly winds. Temperatures varying from 40s to low 50s in cooler valleys at upper elevations to the lower 60s.
Sunday Afternoon
Partly cloudy. Increasing haze and humidity with a chance of a hit or miss shower or thunderstorm. Light SE-S winds. Temperatures varying from low-middle 70s to the lower 80s ( coolest at upper elevations ).
Sunday Night Into Monday Morning
Becoming cloudy with a chance of showers & thunderstorms overnight into morning. Winds SE-S 5-10 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 ft. Winds S to SW 8-16 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures widespread in the 60s to around 70 degrees in warmer locations.
Monday Morning Through The Afternoon
Partly to mostly cloudy with a chance of showers and thunderstorms. Local downpours. Some storms could be strong to locally severe. Winds light SSE-SSW outside of thunderstorms. Temperatures varying from the lower 70s to the lower 80s.
Monday Night Into Tuesday Morning
A chance of showers & thunderstorms. Local downpours. Winds SSE-S at 5-15 mph on mountain ridges and plateaus below 2700 feet. Winds S-SW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures widespread in the 60s. Areas of fog.
Tuesday Through Thursday
Periods of showers & thunderstorms. Locally heavy rain. Afternoon temperatures in the 60s to middle 70s will be common, especially in locations along and north of the High Knob Massif and Tennessee Valley Divide.
Weather Discussion ( Brief Break )
Early Monday ( July 30 ) Update
Increasing moisture levels will fuel intervals of showers and thunderstorms through the coming week. While some storms could become strong to locally severe, the greatest areal threat will be heavy to locally excessive rain amounts.
European Model 500 MB Height Anomalies: Days 1-5
A rather classic heavy rain setting for this time of year is being forecast by the European Model and its 51-Member Ensemble Mean, with general 1.50″ to 3.50″ basin average rainfall amounts during the work week ( implying much heavier local amounts will be possible ).
Previous Discussion
A brief break from the stormy, wet pattern for most of this weekend should be enjoyed before moisture increases again by the beginning of the work week.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A wet Friday afternoon found 1.00″ to 2.00″ of rain falling in the Norton-Wise-Coeburn area, especially over the City of Norton into Coeburn and adjacent northern slopes of the High Knob Massif.
Little to no rain fell to the south at Big Cherry Dam where around 7.00″ of July rain have been measured, illustrating the local nature of heavy Friday afternoon downpours ( more than 4.00″ of rain fell at Big Cherry Dam in the past week to generate overflow ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 3-7
Another deepening upper air trough will set the stage for more heavy to locally excessive rainfall during the last days of July into early August.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
While details remain to be worked out, the European Model ensemble mean is forecasting heaviest rains to fall over the southern Appalachians and along the Coastal Plain as deep tropical flow develops around strengthening Bermuda High pressure in the western Atlantic Ocean.
*Periods of showers and downpours in thunderstorms will continue through Tuesday into Wednesday before a brief decrease in activity, with lower rain chances, develops by Thursday ( July 26 ) as this current upper-level region of low pressure lifts out to the northeast.
Rain chances may remain seasonally low through much of next weekend before ramping back up, but this remains to be seen and will need to be updated as this time period gets closer.
*Another deepening upper-level trough is expected to begin development by next weekend through final days of July, with a heavy to excessive rainfall potential returning by the end of July into the beginning of August.
*This wetter and cooler than average pattern is expected to continue into the final month of Meteorological Summer.
Partly to mostly cloudy. Chance of a shower. Dense fog at highest elevations. Areas of valley fog at lower elevations. Winds SE-S at 10 mph or less, except a few higher gusts on middle-upper elevation mountain ridges. Temperatures in the 50s to lower 60s.
Monday Morning Through The Afternoon
Partly-mostly cloudy. A chance of showers & thunderstorms with hit-miss downpours. Light SSE-S winds. Temperatures varying from the upper 60s to lower 70s to the upper 70s to lower 80s ( coolest at upper elevations ).
Monday Night Into Tuesday Morning
Partly-mostly cloudy. Chance of a shower or storm. SE-S winds at 5-10 mph, with higher gusts, mid-upper elevation mountain ridges. Temperatures varying from the upper 50s to the middle 60s. Areas of fog.
Tuesday Morning Through The Afternoon
Showers & thunderstorms likely. Local downpours. Light winds. Temperatures varying from 60s in upper elevations to the 70s at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide.
Tuesday Night Into Wednesday Morning
A chance of showers and thunderstorms. Downpours possible. Areas of dense fog. Winds shifting SW-W. Temperatures varying from the mid-upper 50s to the middle-upper 60s ( coolest in upper elevations ).
Wednesday Afternoon
Showers & thunderstorms likely. Local downpours. Winds NW to N at 5-10 mph, with higher gusts, on middle to upper elevation mountain ridges. Areas of fog, widespread at the highest elevations. Temperatures varying from 60s in the upper elevations to the 70s at low-middle elevations along and north of the High Knob Massif-TN Valley Divide.
Wednesday Night Into Thursday Morning
Showers & thunderstorms possible through the evening, with local downpours, followed by diminishing activity. Areas of dense fog. Winds WNW-NNW at 5-10 mph, with higher gusts along mid-upper elevation mountain ridges. Temperatures in the 50s to lower 60s.
**Given significant recent rainfall any heavy or slow moving activity could cause strong water level rises during coming days. Remain alert for changing conditions and to NOAA Weather Radio and your favorite media sources for any alerts or warnings which may be needed.
Weather Discussion ( Wet Pattern )
Tuesday Afternoon Update
High Knob Massif Webcam – University of Virginia’s College At Wise
Hit-miss afternoon downpours and cool summer air were featured Tuesday, especially within upper elevations in the High Knob Massif where the daytime max held in the 60s. This contrasted with an afternoon high of 78 degrees in Clintwood where conditions had finally remained dry.
*Temperatures dropped into the upper 50s to low 60s after 5:00 PM as rain fell on Eagle Knob and at High Knob Lake, and also cooled significantly where heaviest rains fell into parts of Powell Valley and the City of Norton into portions of northern Scott County.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Day 4-8
Following a break Thursday ( with low rain chances ) the upper air pattern reloads with jet stream dynamics and a feed of tropical moisture setting the stage for more heavy to excessive rainfall during final days of July into early August ( the final month of Meteorological Summer ).
Previous Discussion
A wet and stormy weather pattern will continue to mostly dominate the mountain region through the remainder of July, with a few breaks ( low rain chances July 26 ) in the more organized activity.
Chimney Rock Gorge of High Knob Massif – July 20, 2018
A general 2.00″ to 4.00″ of rain fell across the mountain area during the July 20-22 period, from the high country of the High Knob Massif north to Breaks Interstate Park.
Totals between 3.00″ to 4.00″ fell on Big Cherry Lake basin and in Clintwood ( 3.26″ ), with 2.10″ measured at City of Norton WP. This boosted July rainfall tallies into the 6.00″ to 7.00″ range on Black Mountain and at Big Cherry Dam in the High Knob high country.
Turk’s-cap Lily ( Lilium superbum ) In High Knob High Country – July 14, 2018
Thursday ( July 26 ) is currently the pick day for lowest rain chances in the short-term as the current upper-level low dissipates and lifts out to the northeast.
This will be short-lived as additional upstream waves in the long-wave pattern begin to dive into the eastern USA and deepen ( i.e., develop ) a new trough. With luck the main impact of this will hold off until late in the upcoming weekend or early next week ( July 29-31 period ).
*While hit-miss showers & thunderstorms will be possible Friday, chances increase significantly tonight into early Saturday with the potential for strong to locally severe thunderstorms approaching from the WNW & NW-N.
Storm Prediction Center Day 1 Risk Regions
*A cluster of strong to severe thunderstorms will need to be closely monitored as it drops southeast to south out of the Ohio Valley Friday evening into the overnight of Saturday.
Storm Prediction Center Day 2 Risk Regions
*A cooler and occasionally wet weekend-early week period is expected as a upper-level low develops and moves south over the region by Sunday into Monday ( July 22-23 ). The coolest conditions will be over the high country where day time temperatures will mainly hover in the 60s ( only near 60 degrees at highest elevations ).
ECMWF Ensemble Mean 500 MB Height Anomalies: Days 1-5
Overnight Into Friday Morning
Partly-mostly cloudy. Small chance of a localized shower or thunderstorm. Areas of dense valley fog. Winds SSE to SSW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from the upper 50s to the mid-upper 60s.
Friday Morning Through The Afternoon
Partly to mostly cloudy. Chance of hit-miss showers or thunderstorms with local downpours. SSE to SSW winds at 5-15 mph, with higher gusts. Temperatures varying from lower-middle 70s to the lower-mid 80s ( coolest in upper elevations above 3000 feet ).
Friday Night Into Saturday Morning
Showers & thunderstorms becoming likely. Some storms could be strong to severe. Locally heavy rainfall possible. Winds SSE-SSW at 5-15 mph, with higher gusts, on mid-elevation mountain ridges-exposed plateaus. Winds SSW-WSW at 10-20 mph, with higher gusts, on upper elevation mountain ridges. Temperatures widespread in the 60s.
Saturday Morning Through The Afternoon
Showers & thunderstorms. Locally heavy rainfall possible. Winds SSW to WSW at 5-15 mph, with higher gusts. Temps varying from the low-mid 60s at highest elevations to the mid-upper 70s.
*Downpours will remain possible through Tuesday as a cold front pushes across the mountains.
*Expect a refreshing air mass to arrive Tuesday night into Wednesday with gorgeous conditions for mid-summer by the afternoon into Wednesday night-Thursday morning.
*A cooler and stormy pattern develops by this weekend into early next week. A heavy to potentially excessive rainfall pattern is being monitored during the July 22-26 period.
Overnight Into Tuesday Morning
Hit-miss showers with a chance of thunderstorms. Winds WSW-WNW at 5-15 mph, with higher gusts, along middle to upper elevation mountain ridges. Areas of dense valley fog. Humid & hazy with temps in the 60s to around 70 degrees.
Tuesday Morning Through The Afternoon
Showers & thunderstorms likely. Local downpours. Some storms could be briefly strong to severe. Winds becoming NW at 5-15 mph, with higher gusts. Temperatures varying from around 70 degrees to the lower 80s ( coolest at highest elevations ).
Tuesday Night Into Wednesday Morning
A chance of evening showers or local storms. Becoming partly-mostly clear and less humid ( increasing high clouds by morning ). NW-NNE winds 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Areas of dense fog developing. Temperatures varying from the low-middle 50s in cooler valleys at upper elevations to the low-mid 60s.
Wednesday Afternoon
Partly cloudy. Blue skies aloft. Pleasant. Less humid. Temperatures varying from the 60s to lower 70s at upper elevations to the upper 70s to lower 80s.
Wednesday Night Into Thursday Morning
Mostly clear and cool. Areas of dense valley fog. NE winds shifting E-SE on mid-upper elevation ridges. Temperatures varying from 40s in colder mountain valleys at the upper elevations to the 50s to around 60 degrees.
Weather Discussion ( Cooler Pattern )
The second half of Summer 2018 ( July 15-August 31 ) will be trending cooler than the first half of this season.
Gorgeous Afternoon at High Knob Lake on July 14, 2018
Although only 2 days have broken 80 degrees at High Knob Lake ( 81 degrees on July 4 being the max so far this year ), and no days have gotten out of the 70s on highest northern slopes in the massif, it has been a much different story for lowlands within the Great Valley where 19 days at or above 90 degrees have already been observed ( mostly in July ).
Daily Climate Date For The Tri-Cities ( July 1-15, 2018 )
Although much more pleasant conditions will be felt by Wednesday into Thursday, a moisture return will occur into this weekend and early next week to set the stage for cool, wet mid-summer conditions. This will be especially true if an upper-level low forms over the region as some recent model guidance suggests.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
A upper trough over the eastern USA at this time of year can be a stormy setup, with relatively cold air aloft over top of low-level moisture. A heavy to potentially excessive rain pattern is being monitored heading into next week.
Stay tuned for later updates on a cooler, wetter pattern.
