Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 202345 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 745 PM EDT Mon Mar 20 2017 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TUESDAY/... 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. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... 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. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... 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. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 745 PM EDT Monday... Slow moving front approaching from the northwest is acting as a focus for elevated convection in the Ohio valley at nose of low level jet. Expect the convection to sink into the region from the north in the next hour or two, and expect enough forcing with modestly steep mid/upper lapse rates to support mention of thunder. The front is in no hurry to clear the region and expect lingering showers mainly in the west to persist through most of the overnight period. The lingering boundary will also start to generate new convection south and west later tomorrow but it does not appear likely to affect TAF sites so will maintain a dry forecast for Tuesday. The flow will become northwesterly behind the front and combine with low level moisture to generate upslope MVFR/IFR low clouds mainly west of the Blue Ridge late tonight into Tuesday morning. Believe the lower cigs will hang in for most of the day in the west, while sites east of the Ridge should become VFR toward daybreak and remain as such through Tuesday. Expect winds to generally remain light through the period. 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...MBS/NF is the U.S. government's official web portal to all federal, state and local government web resources and services.