Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281914 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 314 PM EDT Tue Mar 28 2017 .SYNOPSIS... A cold front will slide east across the region early this evening before exiting offshore overnight. High pressure then works in from the north later tonight into Thursday behind the front. Another storm system moves in from the southwest with showers and storms by the end of the week. && .NEAR TERM /THROUGH WEDNESDAY/... As of 250 PM EDT Tuesday... Surface cold front remains just west of the mountains this afternoon with a preceding surface trough heading into eastern sections, in turn helping to spark overall shallow convection under the exiting cold pool aloft over far eastern sections attm. Expecting the front to finally jump east by early this evening as the residual cold pool exits allowing a somewhat deeper/drier northwest trajectory to develop after sunset. This should bring an end to most eastern showers by early this evening followed by a brief period of upslope clouds/spotty showers mainly northwest sections through early tonight. Upper heights begin to build in the wake of the front overnight with surface high pressure slowly starting to nose in from the north by morning. Thus expecting some clearing espcly Blue Ridge east overnight with more filling in of low clouds mountains later tonight. Expect this along with only weak cool advection to keep lows mostly in the 45-50 range west to low/mid 50s east with some patchy dense fog around espcly valleys and out east where heavier rain has occurred. High to the north will slowly evolve into more of a wedge formation east of the mountains later Wednesday as it builds well to the north. Expect weak sinking motion along with dry air aloft and weak northwest flow to initially allow more sun to develop during the morning before trajectories become a bit more northeast during the afternoon. This may set up a weak convergence zone just east of the mountains where clouds may fill in with heating during the afternoon so boosting clouds a bit. Cant totally rule out a sprinkle or light shower as well but too iffy to include much mention at this point. Otherwise temps dependent upon the amount of insolation before clouds reform so stayed on the low end of Mos which gives 60s mountains to lower 70s southeast. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM EDT Tuesday... Surface high pressure over southeastern Canada will wedge south down the east coast Wednesday night. This wedge is relatively shallow, roughly 2kft feet thick, and will remain mainly along and east of the Blue Ridge into Friday morning. This wedge may bleed just west of the Blue Ridge, into the New River Valley and Alleghany Highlands Wednesday night but will likely erode during the day Thursday. Stratus clouds will accompany this wedge and as the flow becomes southeasterly Thursday morning, light rain/drizzle/fog is possible across eastern slopes of the North Carolina High Country and Grayson Highlands. Southeasterly flow is expected along the south-central Virginia Blue Ridge going into the afternoon and evening to spread light precipitation northward. A once strong low pressure system coming out of the Rockies early this week will track slowly eastward over the Midwest. A weak short wave ejected out ahead of this low will increase rainfall rates across the mountains Thursday evening. This wave will likely erode any wedge environment over the mountains. Rain moving east of the Blue Ridge and over the foothills Thursday night may enhance the wedge some. However, rain will be relative warm to keep enhancements minor. The upper level low will open as it tracks over the Ohio-Tenn Valleys Thursday night. A stronger ejected short wave is expected to track from the southern Appalachians and along the Blue Ridge Friday morning. This wave also appears to track along the western wedge boundary. High rainfall rates and mixing will erode what is left of the wedge through the day Friday. The upper level trough swings over the region Friday afternoon and evening pushing heaviest precipitation east. Some scattered mountain showers are expected with the passing of the trough/cool pool with all rain ending by midnight. Overnight lows Wednesday night will fall into the mid to upper 40s. With a wedge in play and light rain forecasted, temperatures Thursday will only warm into the lower 50s. Areas outside of the wedge, such as Bluefield and Richlands, could see temperatures in the lower to mid 60s. Winds remain southeasterly and the atmosphere saturated. Temperatures may fall some during the evening then rise through the early morning hours as the wedge erodes. With the removal of the wedge Friday and despite copious amounts of rain falling, temperatures should manage to recover into the low to mid 60s by the end of the day. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM EDT Tuesday... Surface high pressure builds over the region Saturday, however drier air does not enter the area until Saturday night. Lingering theta-E ridge will likely result in a good amount of fair weather cumulus clouds over the area, becoming clear in the evening. Conditions remain dry into Monday morning, then we wait on the next system tracking across Texas to the Tennessee Valley Tuesday. Precipitation pattern may be similar to Thursday-Friday`s event with light rain over a weak wedge followed by short waves from an upper level low/trough to our west. Temperatures Saturday will be near normal with above normal temperatures Sunday. Temperatures cool down Monday with rain falling into a wedge. Tuesday will be wet with slightly above normal temperatures as wedge erodes. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... As of 1245 PM EDT Tuesday... Bands/pockets of showers continue to develop and push east across the mountains under the upper cold pool aloft seen passing across the region early this afternoon. Lower cigs and vsbys within the vicinity of this rainfall will continue to bring periods of sub-VFR mainly across the mountain locations through at least mid afternoon, with perhaps some deeper convection over the east prior to early this evening. Thus thinking best thunder threat mainly from KROA east to KLYH/KDAN so keeping in VCTS mention at these spots given isolated nature. Will also see upslope lower cigs redevelop around KBLF late including patchy dense fog at KBCB/KLWB and perhaps KLYH/KDAN which could bring periods of MVFR to IFR overnight. Cold front associated with the upper low will finally work through the region this evening allowing clearing to develop as deeper northwest flow develops. However MVFR bkn cigs seem likely at KBLF this evening into the overnight, and perhaps at KLWB/KBCB with northwest flow taking shape, and some spillover of low clouds late. High pressure slowly builds in from the north on Wednesday with a low level wedge of cooler air developing east of the mountains. Should see some drying under the increasing subsidence but also some uncertainty with the degree of residual cloud cover given heating and flow turning light northerly. This suggests that KBLF may stay sub-VFR into Wednesday morning with perhaps low end VFR cigs possible elsewhere by the end of the valid TAF period. Extended Aviation Discussion... High pressure continues to build in from the north Wednesday night into Thursday with the next storm system moving in the Mississippi Valley Thursday night into Friday. A threat for sub- VFR cigs appears likely as the high wedges southwest Wed night into Thursday for most sites bringing widespread low cigs and possible light precip. The highest probability of rain will be on Friday along with sub- VFR cigs/vsbys with the showers. Post-frontal northwest flow sub- VFR into Saturday mountains with gusty northwest winds possible. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...RCS LONG TERM...RCS AVIATION...AMS/JH/WP

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