Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201959 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 359 PM EDT Mon Mar 20 2017 .SYNOPSIS...
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Low pressure will push up the Ohio River Valley this evening, and cross the Appalachians overnight, triggering showers and isolated thunderstorms as a warm front lifts across the mid Atlantic. As the low progresses east, a cold front will push south across the area as high pressure builds in from the upper Midwest.
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&& .NEAR TERM /THROUGH TUESDAY/...
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As of 345 PM EDT Monday... Currently keeping an eye on a complex of showers and thunderstorms over central Indiana which are associated with a low pressure system that is advancing up the Ohio River Valley this afternoon. Weather forecast models are in good agreement that this low will pass across the central Appalachians overnight, with the associated showers and possibly isolated thunderstorms advancing to the Interstate 64 corridor shortly before midnight. Believe this convection will begin to diminish as it drifts southward toward the North Carolina/Virginia state line as winds in the wake of the cold front dragging behind the low shift increasingly westerly and downslope. Despite frontal passage, cold air does not yet truly enter the area, and overnight low temperatures will hold in the 40s nearly areawide. Through late Tuesday morning, expect residual rain shower activity to linger along the ridges of southeast West Virginia through the highlands of North Carolina, as well as in the vicinity of the passing cold front south of Highway 460 across the Piedmont. Latest forecast model solutions have become a little faster with the passage of the front, indicating less instability than previously called for along the southern end of the forecast area during the afternoon where temperatures are expected to rise into the 70s. Still, cannot rule out a slight chance of thunderstorms from late morning through mid afternoon across the south, though instability will be minimal. Scattering of clouds during the afternoon will promote high temperatures in the low/mid 70s across the Piedmont, while areas along and west of the Blue Ridge will hold in the 60s.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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As of 300 PM EDT Monday... Models are trending faster and further to the south with a west-to- east oriented frontal passage Tuesday night. Even though models have most of the area dry by midnight, we decided to cut PoPs by half going from 60 percent to 30 percent. The highest PoPs remain along the VA/NC border south. The dew point front lags behind with the colder, drier air not entering the northern portion of the CWA (Lewisburg Wv-Lynchburg VA) until around sunrise Wednesday morning. Therefore, leaned toward the warmer MET guidance Tuesday night with most areas staying above freezing with the exception of higher ridges across Greenbrier County to the Alleghany Highlands. Moisture should be gone by the time cold air filters into the area Wednesday to limit accumulating snow to these ridges. High pressure will build in from the north Wednesday. The coldest air should not sink south until Wednesday evening as the center of the high wedges south across the piedmont. Wednesday temperatures will range from the upper 40s to lower 50s west to upper 50s-lower 60s east Wednesday. Cold air Wednesday night will send temperatures down into the mid to upper 20s across the forecast area. We will see uniform temperatures Thursday in the upper 40s to lower 50s as dry cool wedge engulfs the region.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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As of 300 PM EDT Monday... Cool wedge of high pressure will begin to move off the VA/NC coast Thursday night. As the center of the wedge tracks east, a warm front will push moisture over the mountains which should only result in an increase in cloud cover Friday and Friday night. However, a bubble high will likely remain east of the Blue Ridge and over the foothills and piedmont counties into Friday night. This bubble of cool air and easterly flow will keep high temperatures east of the Blue Ridge close to 60F while the mountains warm into the lower to mid 60s. The wedge should be completely erode out of the region by Saturday afternoon with temperatures warming into the mid 60s to lower 70s across the forecast area. An area of low pressure is expected to track from the Midwest Saturday night towards the Ohio Valley Sunday. This system has the potential to bring severe weather to the region Sunday and Sunday night. The track of the system and timing of prefrontal convection into the region will be the biggest influence on how widespread severe potential may become.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... As of 200 PM EDT Monday... Keeping an eye on a decaying complex of showers approaching BLF from the west. Expect brief shower activity between the 19Z to 21Z timeframe, but should still maintain VFR conditions. The next complex of showers and a few thunderstorms associated with an approaching wave of low pressure is already developing across Indiana this afternoon, and will enter into the northern forecast area during the 21/02Z to 21/04Z timeframe. The low pressure system and associated convection will pass southward across the forecast area overnight, stalling toward dawn along the North Carolina/Virginia border. Winds will shift more westerly as the low passes, with ceilings lowering to low VFR in the Piedmont and MVFR/IFR across the mountains. Models indicated that with winds gradually turning more northwesterly after daybreak Tuesday, clouds east of the Blue Ridge will scatter, allowing strong heating to take place. Spotty thunderstorms will be possible across northern North Carolina and extreme southern Virginia during early/mid afternoon, before drier and more stable air pushes in during late afternoon to diminish thunderstorm chances. Another wave of low pressure will pass along the front during the evening, driving the boundary further south. Extended Aviation Discussion... High pressure builds in for Wednesday which should improve ceilings back to VFR. By Thursday the high will wedge in from the northeast, so will remain mainly VFR. It is possible that residual lower ceilings may get trapped especially along and east of the Blue Ridge Wednesday night into Thursday, resulting in possible MVFR ceilings. Dry and warmer weather is expected on Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...NF NEAR TERM...NF SHORT TERM...RCS LONG TERM...RCS AVIATION...AMS/NF

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