Showers & Tropical Downpours In Thunderstorms Will Occur At Times Into This Weekend-Early Next Week, With Heavy To Locally Excessive Rainfall Possible
Any thunderstorm at this time of year can turn locally strong to severe through coming days along and in advance of cold fronts. Heavy to locally excessive rainfall will be possible with a nearly stationary boundary across the mountain area Thursday-Friday, and again late in this weekend along a stronger cold front.
Much less humid air is expected to arrive behind the second cold front by August 22-25 ( with much cooler nights ).
Tuesday Night Into Wednesday Morning
A chance of hit-miss showers & thunderstorms; otherwise, partly cloudy. Areas of fog. Winds SW-W 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures in the 60s to lower 70s.
Wednesday Afternoon
Partly-mostly cloudy. A good chance for showers & tropical downpours in thunderstorms. Humid. SW-WNW winds 5-10 mph. Temps varying from lower 70s at highest elevations to the lower 80s ( warmer south toward the Great Valley ).
**Updated Forecast Below**
Overnight Into Thursday Morning
A chance for showers. SW-WSW winds 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges-plateaus. Humid & hazy. Areas of fog. Temps widespread in the 60s to near 70 degrees.
Thursday Afternoon
A good chance for showers & tropical downpours in thunderstorms. WSW-WNW winds 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges-plateaus. Temperatures varying from 60s to lower 70s at highest elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Thursday Night Into Friday Morning
A chance of showers & thunderstorms. Areas of dense fog. Light winds. Temperatures widespread in the 60s.
Friday Afternoon
A good chance for showers & tropical downpours in thunderstorms. Light winds. Temperatures varying from 60s to lower 70s in upper elevations to the middle 70s to lower 80s ( warmer south into the Great Valley ).
Weather Discussion ( Some Changes )
It is clear now that the boundary will stall across the mountain area, with a continued any place and any time type of pattern featuring intervals of showers & tropical downpours in thunderstorms ( as somewhat drier air does work in north toward the Ohio River ).
Developing Cumulonimbus Along Outflow Boundary – August 17, 2016
For the second day out of three another line of thunderstorms moved across the Cumberland Mountains with heavy rain and booming thunder. With locally more than 2.00″ of rain falling during Monday-Wednesday ( August 15-17 ), this increases the concern for too much rain in places through coming days.
*More than a foot and one-half ( 18.00″ ) of rain has fallen in the City of Norton this summer, with locally higher amounts in the area. This also increases the potential for more rapid run-off if heavy rainfall develops or becomes prolonged in nature.
NAM 12 KM Model Total Rainfall Forecast To 8 AM Sunday – August 21, 2016
Heavy rain will be likely along a stronger cold front later Sunday into early Monday, beyond the forecast period above, such that the potential exists for hefty amounts ( at least in places ).
The Bottom Line…The mountain area will have to wait a while longer to enjoy much drier air, with a stalling boundary set to keep showers & tropical downpours in thunderstorms in the forecast into this weekend when a second, stronger cold front will finally push the high dewpoint ( muggy ) air southward early next week.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible warnings and/or advisories that may be needed through coming days.
Previous Discussion
Rainbow Amid Cumulus Over Long Ridge – August 14, 2016
Weather conditions during the past few days have been straight out of “Beauty And The Beast” with a gorgeous rainbow-cumulus combination being captured over the Tennessee Valley Divide, in southern Dickenson County, by Wayne Riner on Sunday, followed by a beast of a squall line that blasted across Lee, Scott-Wise counties into Dickenson and portions of Russell-Buchanan counties on Monday PM.
Turbulent Clouds Develop In Advance Of Squall Line – August 15, 2016
Hundreds of homes lost electricity due to strong winds and lightning hits as the squall line passed. Rainfall was torrential into Lee, Scott, and Wise counties with 1.00″ to 1.50″ occurring within only 30-45 minutes from The Cedars to High Chaparral.
Wes Ward reported 0.61″ of rainfall at the City of Norton Water Plant ( 3.74″ August / 17.78″ during Summer / 39.06″ in 2016 ) as rain did diminish upon crossing the High Knob Massif ( versus double that much along the windward side of the massif ).
University Of Virginia’s College At Wise
The main corridor of thunderstorms developed over the Great Valley on Tuesday afternoon, as we now begin to enter a “any place and any time” type of pattern along a stationary boundary that tries to slip south a bit by late Thursday to reduce storm chances in the Cumberland Mountains for a short period ( with perhaps, more refreshing air being felt briefly on northerly flow ).
Daily August National Weather Service Statistics – Clintwood
While air temperatures have not been even close to those in the Great Valley, where 44 days of 90+ degree heat have been officially recorded for the Tri-Cities, high humidity levels continue to be nearly relentless in all locations.
*Mixing with breezy to gusty winds making the air along and north of the High Knob Massif feel somewhat more refreshing August 16 in wake of the vigorous Monday storms.
National Weather Service Station In Middle Elevations – Nora 4 SSE
Day-time MAXS varied from 70s above 3000 feet to the low-mid 80s across Wise & Dickenson counties ( 85 degrees in Clintwood ) on August 16 versus another blazing day ( with 95 degrees ) in the Tri-Cities of the Great Valley.
NAM 12 KM Model Total Rainfall Forecast – Tuesday AM Run
The first of two cold frontal boundaries begin to have more impact on local weather Wednesday into Thursday, with the potential for locally heavy-excessive rainfall.
NAM 12 KM Model Total Rainfall Forecast – Early Tuesday PM Run
If this first boundary can slip a little south, somewhat more refreshing air will be felt on northerly flow by Thursday PM into Friday morning.
Although I now have that in my current updated forecast, this remains to be seen and will be dependent upon the boundary’s position come Thursday afternoon-evening.
European 51-Member Ensemble MEAN 850 MB Temp Anomaly Forecast – DAYS 6-10
A more consistent trend is the arrival of much less humid air by early-middle portions of next week, in wake of the next cold front, with the biggest differences being felt by night with cooler temperatures ( especially in valleys ). Fingers crossed this trend will continue to hold.
