The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development During Wednesday & Wednesday Night
Storm Prediction Center Risk Regions
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 ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A wetter and cooler than average week ( much cooler than average by Thursday ) is expected to rule the domain of the southern Appalachians.
NAM 12 KM Model Total Rainfall Forecast To 8:00 PM Thursday ( May 25, 2017 )
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.
GFS Model Total Rainfall Forecast To 2:00 AM Friday – May 26, 2017
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 ).
NAM 12 KM Model Total Rainfall Forecast NEXT 60-Hours ( To 8 AM May 24, 2017 )
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.
GFS Model Total Rainfall Forecast NEXT 60-Hours ( To 8 AM May 24, 2017 )
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 ).
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 1-5
MIN temperatures in the 30s will be possible in high mountain valleys, at least, of the High Knob Massif by later this week.
