Area Forecast Discussion
Issued by NWS Blacksburg, VA

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669 FXUS61 KRNK 201938 CCA AFDRNK Area Forecast Discussion...CORRECTED National Weather Service Blacksburg VA 338 PM EDT Thu Oct 20 2016 .SYNOPSIS...
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A cold front will slowly move into the region from the west tonight, then exit the area to the east late Friday morning. This will spread showers and possibly a few thunderstorms across the Appalachians and central mid Atlantic region later tonight into Friday. Strong gusty winds behind the front will usher in much colder air for the weekend, and some wet snowflakes are possible at the higher elevations west of the Blue Ridge.
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&& .NEAR TERM /THROUGH FRIDAY/... As of 330 PM EDT Thursday... Expect quiet weather into this evening before the cold front approaching from the west can start to push some showers into the region. Guidance continues to trend slower with this system and the bulk of the precipitation looks to remain west of the Blue Ridge until well after Midnight. However, there will be a tight gradient to the precipitation so a few miles either way will make a big difference as to whether locations far west of the Ridge making it into some decent rainfall earlier tonight. Steep lapse rates aloft will also make for the possibility of some embedded thunder especially far west, with the thunder chances decreasing overnight. The front looks to be right along the Ridge by daybreak, but the best forcing will be shearing off to our north. This is expected to weaken the precipitation considerably as it progresses east of the Ridge but some redevelopment of convective elements will be possible in the piedmont early in the afternoon. Conditions will improve as the front departs, but upslope winds will keep scattered going west of the Ridge through Friday afternoon. Winds behind the front will shift around to the northwest and favorable momentum transfer indicated in model soundings will make for quite gusty conditions, especially at the higher elevations from the Blue Ridge westward. Expect the winds to be on the increase after daybreak and continue blowing throughout Friday. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 330 PM EDT Thursday... This portion of the forecast to be dominated by sharp upper trough rotating across the mid-Atlantic region with attendant cold front pushing well off the east coast east Friday night into Saturday. Lingering rain and few high elevation snow showers will persist into early Saturday with a diminishing trend as the day progresses. 850mb temps fall below 0C Friday night and should allow for some snow or mixed precipitation in the elevations above 3000 ft. as noted. Strong winds may well be the most notable feature of this system as deepening low over the northeast increases pressure gradient through Saturday. Wind gusts over 30 mph will be common through this period. In addition some of the coolest temperatures of the season to date are expected although that is not saying much given the extraordinary persistence of above normal temperatures over the past six to eight weeks. Lows Saturday morning upper 30s to low 40s and similar on Sunday morning. No widepspread frost or freeze is anticipated as clouds and wind Friday night and wind Saturday night persist enough to maintain mixing and poor radiational conditions both mornings. The lows in fact will be right around the long-term normals for the 3rd week in October. Saturday will feel quite chilly perhaps owing to clouds/wind and highs from mid-40s west to near 60 east. Those are 5-10F below normal. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 330 PM EDT Thursday... Surface low pressure and associated upper system will be located over southeast Canada on Sunday with the flow across the lower 48 beginning to flatten out into a zonal pattern. This will promote a rather dry week ahead with few temperature extremes. A mostly dry front will push south across the area on Monday with only the slightest chances for some light precip in the far northwest. Not until about late Thursday does another front organize over the midwest and begin advancing eastward. This front looks to arrive early Friday with timing not too dissimilar to tonights frontal passage and again with best dynamics and deeper moisture to our north. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... As of 245 PM EDT Thursday... VFR conditions will persist for a few more hours ahead of the cold front approaching from the west. Some shower activity may develop ahead of the main body of precipitation associated with the front, but confidence in this is low so will not include in TAFs west of the Blue Ridge and focus on the front. Expect several hours of persistent rain with some embedded thunder possible mainly after Midnight for sites west of the Ridge. As best dynamic forcing shears off to our north and west expect precipitation to be sluggish and lessen a bit as it continues eastward, reaching KLYH and KDAN close to daybreak. The precipitation will be accompanied by IFR conditions due to cigs and vsbys. Behind the front, conditions will improve east of the Ridge but as winds veer to NW upslope conditions will only allow for marginal improvement at KBLF and KLWB. Also, as winds veer around to NW the energetic low level flow will mix down and create gusty conditions toward the end of the TAF period with some gusts AOA 30KTS possible. Extended aviation discussion... A return to VFR conditions is expected for most areas Friday night into Saturday. The exception will be western parts of the region where a healthy northwest upslope flow, and lingering low level moisture, will prolong an IFR/MVFR ceiling during this time period. Even the mountain areas will become VFR again for Sunday and Monday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...PC LONG TERM...PC AVIATION...MBS/PM is the U.S. government's official web portal to all federal, state and local government web resources and services.