Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 200530 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 130 AM EDT Mon Mar 20 2017 .SYNOPSIS... High pressure will build overhead tonight and remain in place into early Monday. The center of the high shifts south Monday afternoon in advance of a weak cold front that will drop southeast through the area on Tuesday before stalling. Weak low pressure riding along the front looks to bring another round of precipitation later Tuesday into Tuesday night, ahead of chilly high pressure that will build in from the north during midweek. && .NEAR TERM /THROUGH TODAY/... As of 923 PM EDT Sunday... Moisture stuck in the low levels across southeast WV and portions of the Alleghanys will continue to trend lower overnight as drier air works in from above. Should be clear to partly cloudy by dawn. Temperatures on track to reach the mid 20s to lower 30s across most of the forecast area. Previous afternoon discussion... Low clouds remain slow to go espcly over the mountains given heating beneath cold air aloft within a trapping inversion. However expect a continued slow decrease in moisture from south to north over the west this evening, and with loss of heating out east where caught on the back of the exiting cyclonic circulation passing offshore. Latest guidance generally supports this although a couple solutions tend to flop low clouds back across the far west as the flow turns more westerly through midnight. Since this appears possible left clouds in a bit longer than guidance in spots out west while trending more clearing elsewhere. With surface high pressure building overhead after midnight under shortwave ridging aloft, expect clearing all sections later as forecast soundings show drier air aloft finally squashing the low level inversion from top down. This should also allow for good radiational cooling late as winds decouple and despite steadying warming aloft, expect lows in the 20s valleys and around 30 east. Ridges likely to steady or warm some late given warm advection aloft so kept spots across the far west a little warmer. Upper ridge starts to flatten some on Monday as surface high pressure shifts to the south. This will open the door for increasing moisture advection from the west ahead of a weak disturbance and its associated cold front heading east from the midwest. However most forecast soundings show most cloudiness other than the mid/high variety holding off until afternoon with the boundary layer overall remaining dry for most of the day across the west. Thus will go with more sun early followed by increasing clouds from west to east by mid to late afternoon. Latest Nam still showing that a few light showers could make it into the far northwest by sunset so left in a low pop mainly Greenbrier Valley but dry elsewhere. Backing westerly flow and surge in 850 mb temps should finally push highs to above normal levels with most in the 60s except for a few 50s at elevation. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... As of 230 PM EDT Sunday... Monday night, a weak cold front will move into, and then stall across the area during the day Tuesday. A reinforcing cold front will progress into the region on Tuesday afternoon and evening, along with a shortwave trough moving within a prevailing longer wave pattern. The result will be isolated to scattered rain showers moving into the area from west to east Monday night. On Tuesday, increased dynamics and instability will yield greater coverage of showers, along with the potential for some isolated thunderstorms across roughly the southern half of the region during the afternoon. The showers will continue into the Tuesday night, until the reinforcing cold front exits the southern half of the region early Wednesday morning. High pressure quickly moves into the area during the day Wednesday, and continues building into the area Wednesday night. Temperatures during this portion of the forecast will average ten to fifteen degrees above normal on Tuesday, but trend to ten degrees below normal by Wednesday afternoon and night. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 245 PM EDT Sunday... High pressure over the mid-Atlantic states will help to keep the region relatively precipitation free through at least Thursday. As the center of the high creeps east, clockwise flow around the high will draw increasing moisture and higher temperatures back into the area by the start of the weekend, in the form of patchy light rain. Saturday night into Sunday, a cold front is expected to cross the area. Look for increasing chance of showers during this time frame, with a slight chance of thunderstorms Sunday afternoon across western, southern, and eastern portions of the region Temperatures during this portion of the forecast will be around ten degrees below normal on Thursday, but trend to readings about ten degrees above normal by Sunday. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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As of 125 AM EDT Monday... High pressure will continue building over the region tonight. This will bring VFR conditions to locations east of the Blue Ridge. Lingering low level moisture over the central Appalachians will continue erode overnight. High confidence that KLWB will improve to VFR by 12Z/8AM. Mid/high clouds will be increasing by the afternoon ahead of an approaching frontal system with sub VFR cigs toward the end of the valid period in the mountains, though any precipitation looks to hold off until after 06Z/2AM Monday night. Winds will generally be light. Extended Aviation Discussion... Moisture ahead of a cold front and associated weak low pressure will arrive by Monday night, with precipitation and sub-VFR possible later Monday night in the mountains and in all areas Tuesday into Tuesday night before conditions improve back to VFR by Wednesday afternoon. By Thursday high pressure will wedge in from the northeast so will stay VFR though some residual lower cigs may get trapped espcly along the Blue Ridge Wednesday night into Thursday resulting in possible MVFR cigs.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/WP SHORT TERM...DS LONG TERM...DS AVIATION...AMS

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