Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211158 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 758 AM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure across the mid-Atlantic will gradually take up a position off the coast, allowing winds to turn southerly and bring a return of deeper moisture to the region along with a chance for showers and thunderstorms mainly along and west of the Blue Ridge. A cold front will approach the area by the middle of the week, bringing a better chance for showers and storms to the Appalachians and central mid Atlantic region. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM EDT Monday... High clouds over the region are allowing for radiational cooling this morning, driving the development of patchy dense valley fog mainly west of the Blue Ridge. Expect the fog and stratus to linger past dawn before dissipating by early to mid morning. Flat ridging in quasi zonal flow aloft will combine with a surface high taking up position as Bermuda high off the coast to keep warm and humid conditions across the region as we start the work week. While the warm and moist conditions will help generate surface based instability, BufKit soundings show some capping warmth aloft that will suppress convection. Expect orographic forcing along and west of the Blue Ridge will give enough support to updrafts for a chance of showers and thunderstorms mainly from the Ridge westward this afternoon into this evening. Diurnal heating will start to drive convective cloud development by late morning, but coverage at least through the start of the eclipse should allow for some viewing with clouds decreasing heading off to the southeast across Southside VA and the piedmont. Note that the presence of clouds will still not make for safe eclipse viewing without the proper certified eye protection. Convection will dwindle with loss of heating this evening, yielding dry conditions for Monday night with the possibility for more valley fog toward daybreak Tuesday. Highs today will generally be in the lower 90s east of the Ridge with 80s to the west. Lows will be around 70 east to generally the middle 60s west. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 330 AM EDT Monday... On Tuesday, high pressure drifts further east into the Atlantic. Return southwesterly flow on the back side of this high will bring more heat and humidity into the region. Upslope flow along the Blue Ridge and a lee trough over the piedmont may produce a few storms across the mountains Tuesday afternoon, especially in favored areas on the southern and eastern slopes. Increase mixing ahead of an approaching cold front may be a deterrent to limit convection activity to scattered coverage pre-frontal passage. Any afternoon storms should fade during the evening, with best forcing delayed until after midnight. The cold front progress in from the Ohio Valley after midnight and before dawn, with decaying convection already ongoing. Best chances of seeing a strong storm will be early Wednesday morning as the front moves in from the west, and late Wednesday evening as convection reforms on the lee side of the Appalachians. With the passage so far removed from proper heating, will likely keep even thunder at a minimum, except during these time periods. Muggy conditions are expected through Tuesday evening, with highs in the 80s west of the Blue Ridge and low 90s east. A bit cooler on Wednesday mainly due to showers/cloud deck. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 330 AM EDT Monday... A bit of uncertainty remains on how far and fast the front will progress from our area. Guidance seems to be settling on a bit slower progression, but also kicks POPs/QPF out of the region for good by early Thursday morning. Behind the front, cooler and drier conditions settle in for most, with temperatures in the middle 70s (West) and lower 80s (East) into next weekend, where a wedge-like pattern takes shape. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 745 AM EDT Monday... Surface observation indicate patchy fog across the mountains this morning, mainly in the river valleys. However, bands of mid level clouds continue to pass across the area, limiting radiational cooling and resulting in up and down visibilities. At any rate, with another day of strong heating, fog will burn off quickly after 9 AM, resulting in widespread VFR conditions. Flat ridging in quasi zonal flow aloft will combine with a Bermuda high at the surface to keep warm and humid conditions across the region this TAF period. While the warm and moist conditions will help generate surface based instability, BufKit soundings show some capping warmth aloft that will suppress convection. Expect orographic forcing along and west of the Blue Ridge will give enough support to updrafts for a chance of showers and isolated thunderstorms mainly from the Ridge westward this afternoon into this evening. Will go with VFR conditions at all sites. Any convection will dwindle with loss of heating this evening, yielding dry conditions for Monday night with the possibility for more valley fog toward daybreak Tuesday. Winds will be light through the period. Extended Aviation Discussion... Moisture will continue to increase on Tuesday as high pressure moves farther offshore ahead of another cold front that will arrive from the northwest around midweek. This will again lead to more afternoon clouds and isolated convection mountains Tuesday afternoon but overall VFR at this point. Better potential for sub- VFR will come Wednesday when more widespread showers and storms arrive with the next cold front. Flying conditions should slowly improve behind the passing cold front on Thursday although sub-VFR cigs may linger across southern/western sections a while longer. && .EQUIPMENT... As of 400 AM EDT Sunday Aug 20th... KFCX doppler radar expected to be down for the rest of the month due to a failing bull gear. Technicians are working on the radar through this week and the radar will most likely stay down completely as the repairs are being made. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...JM LONG TERM...RCS AVIATION...MBS/NF EQUIPMENT...RAB/WERT/WP

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