Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 200617 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 217 AM EDT Thu Oct 20 2016 .SYNOPSIS... A front extended from New England through the Ohio Valley to a low over the Southern Plains. This low will track across the Tennessee and Ohio Valleys by Friday morning and will push a strong cold front across much of the eastern United States Thursday night and Friday. High pressure build in behind the low on Sunday and Monday. && .NEAR TERM /THROUGH TODAY/... As of 800 PM EDT Wednesday... No significant changes needed at this time. Made some minor adjustments to pops across the north as isolated showers have developed just across the RNK CWA border in the LWX CWA/Central VA along the stalled frontal boundary. HRRR indicates that these may persist for a couple more hours, then dissipate. Not expecting anything elsewhere overnight and in general rain chances decrease overnight, not increase. Temperatures generally on track after a hot day with temperatures in the 80s to near 90! As of 325 PM EDT Wednesday... Little change in the 500MB pattern is expected tonight with the upper ridge over the southeast United States. Heights begin to fall on Thursday. Surface front stalled from the Ohio Valley to a low over the Southern Plains will lift north as warm front late tonight and on Thursday while the low crosses through the Ohio Valley. Clouds along the front will cover some of the forecast area north of a Lewisburg to Lynchburg line tonight...before lifting north out of the area by Thursday morning. Models were in decent agreement with the timing of clouds and precipitation for Thursday afternoon, so have slowed down arrival time of the probability of precipitation in the west until after 5PM. Temperatures will be mild overnight. Stayed close to lows from Wednesday or a couple of degrees warmer. Thursday will be the final day of above normal temperatures. Enough sun to again have a sharp rise in temperatures in the morning, but afternoon clouds in the west will limit much additional heating. Went slightly below guidance over the mountains. && .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/... As of 320 PM EDT Wednesday... Digging short wave energy will sharpen the upper trof considerably as it approaches the region from the west and push a strong cold front through the area. With much of the flow parallel to the front and best dynamics shearing off to our north it will be a slow FROPA west to east from late Thursday night through Friday morning, respectively. This will give us gradually deteriorating conditions through early Thursday night with the best chances for precipitation looking to hold off until after Midnight for most of the area. Will also include a slight chance for embedded thunder mainly west as steeper lapse rates aloft may tap some of the dynamic energy before it shears off to our north to boost convective elements a bit. As a large area of high pressure over the Mississippi valley ushers in significantly colder air behind the front, the low level flow will become energized and make for blustery conditions for Friday and into the weekend. There will also be the prospect for the first snowflakes of the season Friday night and possibly again on Saturday night in upslope flow at the higher elevations west of the Blue Ridge but nothing of any significance expected. On a related note, low temperatures at or below freezing may well end the growing season for some higher elevations west of the Blue Ridge Friday night. Expect temperatures west of the Ridge to be falling throughout Friday, then begin falling across the piedmont by the afternoon. Highs on Saturday will only be in the upper 40s/lower 50s west to around 60 east, with the blustery wind making it feel even colder. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 320 PM EDT Wednesday... The upper pattern will be trending toward reestablishment of an upper ridge over the eastern US through the middle of next week. This will generally keep our weather quiet and dry through the period. Return flow around high pressure to our south will push some warmer temperatures into the region for Sunday and Monday. A fast moving short wave will zip through the Great Lakes region and drive a low through New England. This will swing a weak cold front through the region later on Monday afternoon with any precipitation expected to remain off to our north. Cooler high pressure will then build in on Tuesday and take up a wedge position east of the Appalachians by Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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As of 200 AM EDT Thursday... A stalled frontal boundary was evident from northern WV through northern/central VA. This front will return north as warm front Thursday. High pressure aloft will gradually weaken through Thursday as a deepening upper trough and associated strong cold front sweep through the region Thursday night into Friday. Generally VFR conditions are expected to continue through this TAF valid period, although will will have to contend with areas of mvfr vsby this morning with local ifr/lifr due to dense fog in some of the river valleys. Fog is expected to be shallow, and will burn off quickly after sunrise. Once the fog has dissipated, expect VFR for the remainder of the day. As for precipitation threat, all models suggest that associated frontal convection/precipitation will not reach the western part of the RNK CWA (BLF and LWB TAF sites) until just after 00Z Fri (8pm Thursday). The air mass in advance of the front is very stable with unseasonably warm temperatures aloft providing a strong cap on convection as well as clouds. Precipitation associated with the front will largely be post-frontal, not pre- frontal. Thus, will not introduce any precipitation until closer to midnight for BLF and LWB and well after midnight for areas east of the Blue Ridge. With respect to clouds, model soundings indicate a strong inversion around the 850mb-800 mb layer, resulting in continued SCT cloud development in the 050-070 layer. This should be the case throughout the day Thursday, becoming BKN late in the day western areas as the frontal system approaches from the west. Cloud bases are expected to remain mostly VFR through the TAF valid period. Winds to remain mostly calm or light SSW-SSE through 14z/10am Thursday, becoming SW 7-10kts after 14Z Thu, with low end gusts up to 15 kts possible KBLF, KBCB, and KROA by mid to late afternoon. Medium to high confidence in cigs/vsybs through the TAF valid period. Medium to high confidence in wind direction/speed through the TAF valid period. Extended aviation discussion... Showers, perhaps an isolated thunderstorm will develop over the mountains toward midnight Thursday/Friday, with showers spreading east of the mountains as the front moves east Friday morning. The best chance of precipitation will be from midnight Thursday night through noon on Friday. This will be the most likely period of widespread MVFR to IFR ceilings and visibilities. The strong cold front will move through the region from west to east, mainly in the 06Z Fri to 15Z Friday time frame. A southwest to northwest wind shift is expected to occur late Thursday night across the region with gusty northwest winds behind the front continuing into Friday night and possibly Saturday. Areas of sub- VFR conditions will likely accompany the front and precipitation. 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.
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&& .CLIMATE... As of 815 PM EDT Wednesday... Record maximum temperatures... New record max temperatures were set at Blacksburg and Danville today with 83 and 86 degrees, respectively. Record temperatures are possible again one last day, namely Thursday. Oct 19 Location Record Max Bluefield.....81 in 1984 Danville......85 in 1953 Lynchburg.....88 in 1938 Roanoke.......91 in 1938 Blacksburg....80 in 1991 Oct 20 Location Record Max Bluefield.....79 in 1993 Danville......88 in 1984 Lynchburg.....85 in 1993 Roanoke.......84 in 2005 Blacksburg....82 in 1985 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/RAB SHORT TERM...MBS LONG TERM...DS/MBS AVIATION...PM/RAB CLIMATE...AMS is the U.S. government's official web portal to all federal, state and local government web resources and services.