Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 210131 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 931 PM EDT Tue Apr 20 2021 .SYNOPSIS... High pressure will give way to the passage of a strong cold front Wednesday. Expect windy conditions with the passage of the cold front along with falling temperatures. Well below normal temperatures can be expected into early Friday. An area of low pressure will bring rain to the area for the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 920 PM EDT Tuesday... Minor changes to the timing of the cold front Wednesday. A late season winter interlude is taking place over the nations mid section with some very cold air over the nations mid section clashing with warming temperatures in the east. The cold front which bisects this change in airmass is expected to cross our forecast area Wednesday morning. It will be a very noticeable change. For tonight...ahead of the front...isolated showers over the mountains will gradually move move northeast and dissipate. Much of the HiRes guidance had little to no precipitation after 06Z/2AM. Have made minor adjustments to the probability of precipitation and overnight temperatures based on the latest radar and observation trends. For Wednesday...a strong cold front will cross the forecast area between 8AM and Noon, impacting the mountains between 8-10AM and then east of the mountains between 10AM-Noon. Main concerns... Wind...strong gusty winds are expected to accompany the frontal passage with gusts near 40 mph...rain showers helping with the momentum mixdown. Post frontal winds gusting from 25 to 35 mph will then continue through the afternoon and into Wednesday night. Attm do not foresee the need for a wind advisory, but may need to entertain this for the higher elevations if model trends increase. Precipitation...expectation is for showers to be associated with the front with best chance for wetting across the mountains...amounts generally less than a tenth of an inch. Model guidance suggest showers will weaken as they cross the mountains with very little rain anticipated for our foothills and piedmont. There is some potential for showers (thunderstorm?) to re-develop as the front crosses the piedmont, but think this may not take place until afternoon and across an area that would be east of our forecast area...east of South Boston where instability will increase from increasing temperature ahead of the front. On the opposite side of the CWA, cold air is expected to change any lingering moisture over to snow showers, with potential for late afternoon showers supporting snow/graupel, but mainly over the WV/VA highlands. Temperature...with the frontal passage, expect falling temperatures. Even with any post frontal clearing, it will be a struggle for recovery due to strong cold air advection aloft. Current thinking is that temperatures tomorrow morning may turn out to be the highs for the day in the mountains with falling temperatures expected areawide west of the Blue Ridge. East of the Blue Ridge there will likely be a temperature dip associated with the frontal passage, followed by some recovery when the sun pops back out Wednesday afternoon. In addition to the above concerns, there is also a concern that conditions may meet red flag criteria for areas farther east, especially across North Carolina... please see the fire weather section of this AFD for details. In collaboration with our North Carolina land managers and weather offices, a Fire Weather Watch has been issued for areas east of the Blue Ridge...for low RH, wind, and high fire danger. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 200 PM EDT Tuesday... Windy with below normal temperatures through the end of the workweek. Cold and blustery conditions will continue behind the front Wednesday night into Thursday with enough low level moisture to generate some upslope snow/rain showers at the higher elevations west of the Blue Ridge. Winds will be quite gusty especially along the hilltops but it looks like gusts should generally remain at or below 45MPH so no wind headlines planned. Temperatures Wednesday night will be well into the 20s in the mountains and will maintain a Freeze Watch here. Temperatures east of the Ridge will be a bit warmer generally around 30 degrees which lowers confidence on adding these locations to the Freeze Watch so will leave them out for now. Thursday will be another windy day as high pressure builds in and lingering showers subside with temperatures remaining cold as highs only reach the upper 50s/around 60 east, 40s west. Thursday night may require another frost/freeze headline with lows below freezing once again in the mountains and in the low/mid 30s to the east. The center of the high pushes off to the east on Friday and allows temperatures to moderate before the next system approaches from the southwest and pushes precipitation to our doorstep late Friday night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 200 PM EDT Tuesday... Widespread precipitation to start the weekend, then improving conditions with a warming trend into the first part of next week. A potent low pressure system will move across the Appalachians and central mid Atlantic region Saturday into Saturday night. The best dynamics will pass by to our southeast and this should keep any threat for severe storms out of our region, but will watch closely to see if trends start pulling energy closer to Southside and the NC piedmont. As it stands, expect a good dose of rainfall across the region on Saturday into Saturday night with some lingering upslope showers in the mountains into early Sunday morning. Ensemble guidance is then in good agreement in building a large ridge over the eastern US with fair weather and a trend to above normal temperatures through the first part of next week, though we may have to contend with some patchy frost in the mountains again Sunday night. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... As of 920 PM EDT Tuesday... All TAF locations are expected to remain VFR through 12Z/8AM Wednesday. Exception will be late toward 12z Wed when MVFR cigs may be very close to KBLF and KLWB. Gridded LAMP guidance as well as the NBM have ceilings dropping to MVFR along the front. A strong cold front is expected to cross the mountains from west to east Wednesday morning with a significant change in conditions occurring between 12z/8AM and Noon. MVFR cigs are expected across the mountains during this period associated with a wind shift and wholesale increase in wind speed. Expect winds to become northwester with speeds of 15 to 20 kts sustained and gusts of 25 to 35 kts. Snow showers are likely in southeast West Virginia in the afternoon but with VFR visibility. Thunderstorms will develop along and ahead of the front in the afternoon, but the boundary will be east of KLYH and KDAN by that time. Above average confidence in timing of the front, arrival of MVFR ceilings, and wind. Average confidence of areal coverage of precipitation. Extended Aviation Discussion... Strong and gusty winds are likely behind a cold front Wednesday night, with these winds persisting into Thursday before diminishing. Gusts of 25 to 35 kts are likely, the higher gusts occurring along the ridges. Expect VFR Thursday night through Friday under high pressure. Widespread rain with MVFR or lower conditions are expected Saturday and Sunday. && .FIRE WEATHER... Breezy northwesterly winds are expected across much of the eastern seaboard Wednesday afternoon in the wake of a cold front which will move through the region. Most model guidance keeps the frontal passage dry for areas east of the Blue Ridge, especially across the Carolinas. Similarly dry and breezy conditions are anticipated in eastern Virginia, but there is a better chance for precipitation as the front passes through this region. Sustained winds are expected to be 15 to 20 mph with gusts of 20 to 30 mph associated with relative humidity of 25 to 35 percent. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Freeze Watch from late Wednesday night through Thursday morning for VAZ007-009>020-022>024. NC...Freeze Watch from late Wednesday night through Thursday morning for NCZ001-002-018. Fire Weather Watch from Wednesday afternoon through Wednesday evening for NCZ003>006-019-020. WV...Freeze Watch from late Wednesday night through Thursday morning for WVZ042>044-507-508. && $$ SYNOPSIS...PM NEAR TERM...AMS/PM SHORT TERM...MBS LONG TERM...MBS AVIATION...AMS/PM FIRE WEATHER...PM

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