Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211712 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 112 PM EDT Sun Aug 21 2016 .SYNOPSIS... Scattered showers and thunderstorms today ahead of an approaching cold front which will bring cooler and drier air to the region. High pressure will dominate the weather until mid-week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1255 PM EDT Sunday... For this afternoon, a nearly solid line of showers will continue heading eastward across the region. No thunderstorms have occurred yet, but chances will increase as the activity moves into more unstable air in the east. No major changes made to the ongoing forecast. As of 1015 AM EDT Sunday... Forecast update this morning will see its biggest changes across the eastern portions of the area. Have removed the isolated to chance POPs across this region of the area, especially across the southeast portion of the area, until the early to middle afternoon. This adjustment was based upon the latest radar and guidance trends. Have also increased the high temperatures in this area by a degree or two with the later arrival of notable precipitation. As of 345 AM EDT Sunday... Upper trough will rotate across the Great Lakes today with associated cold front pushing from the eastern Ohio Valley at midday through to the Atlantic coast by early evening. Should see a period of showers and possibly a few embedded thunderstorms ahead of and along the boundary today with the best chances for rain in the west and best chances for thunder in the east although will maintain some thunder in the grids as MU Capes briefly reach 500-1500 J/kg from west to east across the CWA in the 12-21z time frame across the CWA per NCEP SREF. SPC maintaining marginal risk in the far eastern counties with that higher CAPE and it may depend on the amount of sun in that area. Best shear will be north of the RNK CWA so any severe threat will be isolated. Rainfall amounts in the 0.25 to 0.75 inch range today seem most probable as the front will make fairly rapid progress with the strong upper support. Rain should be tapering off by around 00z/22 with lingering showers in the far east possible after that time. Don`t anticipate any significant hydro issues with the speed of movement although high PWATS ahead of the front will allow for some pockets of heavy rainfall. After the front much drier air will work into the region which may be a welcome change for some from the remarkably persistent near tropical air mass of recent weeks. Should see lows into upper 50s west to mid- 60s east by Monday morning, the coolest we have seen since about one month ago. And actually those temps are about normal for this date in August which shows how long we have been above normal at night, over 30 days.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY/... As of 330 AM EDT Sunday... Dry cool air will filter into the region Monday as high pressure will be centered over the Ohio Valley. With zonal flow aloft, this high pressure system will drift east over the Appalachian Mountains Monday night, then wedges down the Mid Atlantic on Tuesday. The pattern remains progressive on Wednesday with the wedge center moving off the New England Coast. While this ridge is in the forecast area, temperatures will remain cooler than normal with the mountains being in the 70s and areas east of the Blue Ridge in the low to mid 80s. Humidity levels each day will stay below 50% but will increase on Wednesday as winds become southeasterly. Also with a very dry air in the region, there will not be any showers or thunderstorms in the area until late in the week. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 345 PM EDT Saturday... By Thursday, the surface high continues to drift off shore allowing better return of Gulf moisture into the region. A broad trough in the central U.S. will help drive a weak cold front toward the region late Thursday with a better chance of convection as a result west of the Blue Ridge. The front will continue to move southeast Friday toward the NC Piedmont, then wash out as high pressure aloft once again intensifies across the region. Dynamics are weak both days, but scattered convection can be expected, especially across the mountains, mainly west of the Blue Ridge Thursday, then more to the east of the Blue Ridge across the Piedmont on Friday. Temperatures and humidity levels will be on the increase again during this period as PWATS surge back toward the 2.0 inch mark and 850mb temps creep back toward +20C. The pattern established during the extended period opens the door to potential tropical activity that may be looming the future. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 700 AM EDT Sunday... Scattered showers and isolated thunderstorms are expected today as a cold front approaches the area. Main time window for precipitation at the TAF sites will be 14z to 20z and the better chances for a thunderstorm are in the afternoon at KDAN and possibly KROA/KLYH . Potential for sub-VFR vsbys/cigs will persist until the front clears the forecast area. Once the front moves through after 00z/22 expect gusty northwest winds and a drying trend. Mainly VFR will return for tonight with the exception of morning fog at some TAF sites. Extended aviation discussion... Confidence is high for much drier weather across the region for Monday through Wednesday as High pressure builds overhead, promoting VFR. By Thursday, the center of the high will be far enough east for western portions of the area to see a return of isolated to scattered MVFR showers and a few thunderstorms. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PC NEAR TERM...DS/PC SHORT TERM...RCS LONG TERM...RAB AVIATION...PC/PM

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