Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231838 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 238 PM EDT Wed Aug 23 2017 .SYNOPSIS... A cold front will continue to move southeast tonight. A large high pressure system will move out of central Canada and build eastward behind the front Thursday, bringing significantly cooler temperatures to the region into the weekend. && .NEAR TERM /THROUGH THURSDAY/... As of 238 PM EDT Wednesday... KFCX WSR-88D is back in service ! A cold front with associated showers and thunderstorms will move southeast this afternoon into tonight. Solar heating has created some surface based instability ahead of the boundary reinvigorate convection with the front mainly east of the Blue Ridge mountains. The northwest winds behind front are hindering showers in the west. The best low level winds and dynamic support will be moving by to our north which will greatly limit the potential for any thunderstorms to become severe. The Day One Convective Outlook has most of the forecast area in general thunderstorms, with marginal risk of severe clipping only portions of extreme southeast counties. A large area of high pressure will move out of central Canada and build eastward behind the front, bringing an end to any lingering showers early tonight. Slackening winds west of the Blue Ridge and a cooler airmass should help generate some late night valley fog. Low temperatures tonight will range from the lower 50s in the mountains to the mid 60s in the Piedmont. A broad upper trough will slide east from the Great Lake regions to the East Coast Thursday. This afternoon`s cold front will continue to push south into the Southeast States. During Thursday afternoon, a shortwave embedded within the broad upper trough will rotate eastward into the Mid Atlantic Region. This feature may create clouds to upslope areas of the Alleghanys, with a few showers possible during peak diurnal heating. The NAM was the furtherest south with the southern extent of the isolated showers compared to ECMWF and GFS. High temperatures Thursday will vary from the upper 60s in the northwest mountains of Greenbrier county to the lower 80s in the Piedmont. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 230 PM EDT Wednesday... Some low level moisture in southeast West Virginia along with a weak short wave so some upslope clouds expected. Short wave tracking through the upper northeast trough on Thursday night and early Friday morning will provide some lift. But by Friday morning the 850MB winds forecast to be from the north which is not as favorable for upslope. Slightly cooler temperatures at 500 MB will result in larger lapse rates and instability Friday. NAM and GFS showing an increasing amount of moisture below 700MB Friday night and Saturday and a wedge develops and strengthens. Have lowered minimum temperatures on Thursday night, trending closer to MET guidance. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... As of 1230 PM EDT Wednesday... For Monday models continued to show separation between a northern stream system approaching the Ohio Valley and the tropical system over the Lower Mississippi Valley. Short wave in the southwest flow over the Mid Atlantic region forecast to cross through the area on Tuesday. Confidence in the synoptic scale weather pattern decreases on Tuesday and Wednesday mainly due to uncertainty and spread in the guidance with the evolution of the Gulf of Mexico and southeast coast tropical systems. Surface high pressure moves into southeast Canada with a strong wedge down the east side of the Appalachians by Sunday. Cool air comes down with the wedge by Sunday with 850MB temperatures on Monday and Tuesday in the +8 to +12 range. Models showing abundant low level moisture, especially in the foothills and eastern upslope areas through Sunday. Will cut back the probability of precipitation on Monday but will leave in clouds. Plan to slightly lower maximum temperates Sunday through Tuesday. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... As of 120 PM EDT Wednesday... MVFR convection associated with cold front moving southeast across the region this afternoon into tonight. With the front advancing into the Piedmont during peak heating, expect enough surface based instability to generate scattered showers and thunderstorms along it east of the Blue Ridge this afternoon into this evening. Conditions improving to VFR behind the front as winds become northwest. A large high pressure system will move out of central Canada and build eastward behind the front tonight. Winds will begin to come around to the northeast east of the Blue Ridge overnight as the large surface high begins to translate toward New England. Enough northeast wind should develop overnight to prevent fog across the Piedmont, but good radiational cooling and clearing skies should promote good fog development at LWB and BCB, but not as much confidence as usual with advection of drier air into the region. After any morning fog or low clouds, VFR conditions will prevail Thursday. Any isolated shower may be possible across the extreme northern portion of forecast area. Medium to high confidence in ceilings,visibilities and winds during the taf period. Extended Aviation Discussion... Generally VFR conditions are expected Thursday night into the weekend as high pressure builds over the region. There will also be a diurnal trend for late night fog/stratus especially west of the Blue Ridge with KLWB and KBCB the most likely TAF sites to be affected. Isolated convection may be possible across the mountains Saturday into Monday. && .EQUIPMENT... As of 1205 PM EDT Wednesday... KFCX doppler radar has completed all repairs and is now back in service. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...AMS LONG TERM...AMS AVIATION...KK/RAB EQUIPMENT...KK is the U.S. government's official web portal to all federal, state and local government web resources and services.