Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 211834 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 234 PM EDT Tue Aug 21 2018 .SYNOPSIS... Low pressure moving into the Great Lakes will push a slow moving cold front through the region late tonight and tomorrow, and bring strong thunderstorms to the Appalachians and central mid Atlantic region. High pressure will then build in from the midwest and bring much more pleasant weather to the region for the end of the workweek and into the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 230 PM EDT Tuesday... Robust thunderstorms have developed west of the Blue Ridge. Meso guidance has been handling this situation fairly well and expect storms to continue to develop and strengthen through the afternoon. Instability has exceeded expectations and will continue to fuel storms while short but well curved hodographs show a good amount of low level shear to aid organization. Expect scattered clusters/line segments with shallow rotation capable of producing damaging winds to affect the region through this evening before moving off to our east early tonight. The cold front will ever so slowly work its way eastward across the region late tonight and tomorrow, shifting winds around to the northwest. With deep synoptic moisture this will develop upslope clouds and some sprinkles/drizzle overnight along and west of the Blue Ridge with some downsloping improvement to the east. Conditions will trend upward after daybreak tomorrow. The low level wind field will amplify and start some gusty conditions along the hilltops overnight. The winds will mix down to lower elevations as steep low level lapse rates develop tomorrow morning, making conditions a bit gusty through the afternoon. Instability appears tall and skinny on model soundings tomorrow but lapse rates are steepening and will make for some isolated showers/thunder tomorrow afternoon, especially east of the Ridge. Temperatures tonight will generally be in the upper 60s/around 70 east of the Ridge with low/mid 60s to the west. Highs Wednesday will be in the mid 80s east to mid/upper 70s west. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 230 PM EDT Tuesday... A much quieter and pleasant end to the workweek as a large high pressure builds into the northern mid-Atlantic region and by Friday into southern New England. The main highlight in this period is the much more comfortable humidity levels and period of cooler than normal temperatures. Each day should feature sizable diurnal ranges given dry air both surface (dewpoints in the 40s to mid 50s) and aloft as well as largely clear skies. Our western counties may see some high-altitude haziness to skies as northwest flow aloft may transport the eastern extent of Canadian/western CONUS wildfire smoke well aloft. There should still be enough of a northwesterly gradient wind to preclude overnight radiation fog development Wednesday night, but this gradient will slacken early Thursday allowing for lighter northwest winds during the day. Prospect for nighttime radiation fog may be greater Thursday and Friday nights. With 850 mb temperatures around the upper single digits to low teens Celsius supporting highs in the 70s and lows in the mid 40s to 50s, conditions late this week may draw some comparison to early fall. Indeed, forecast 850 mb temperatures are more ordinarily observed around early October per the SPC sounding climatology. Only small change expected Friday is that the winds should shift to an easterly component. Overall forecast confidence is high, though is moderate on nighttime fog potential. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 230 PM EDT Tuesday... Our stretch of cooler than normal temperatures and low humidity levels is short-lived, as a large heat ridge builds eastward for the weekend. 850 mb temperatures rise to around +18C by the weekend with humidity levels also on the rise. Thus look for a return to more summerlike weather by the weekend and into early next week. Saturday looks dry but a northern-stream upper-level trough may provide enough of a weakness in subsidence to produce a greater coverage of thunderstorms on Sunday. While possible, it`s still early to say with any level of certainty if any may become strong on Sunday. Temperatures should trend more typical of midsummer in this period, trending above normal by early next week. Overall forecast confidence is moderate in this period. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 230 PM EDT Tuesday... Showers and thunderstorms have developed well ahead of a cold front approaching from the west. Expect this convective activity will affect the region until it moves off to the east later this evening/early tonight. Will generally use VCTS and amend when convection appears imminent at an airfield. Cigs will generally be VFR outside of thunderstorms, though conditions down to IFR due to cig/vsby along with heavy rain and gusty wind will likely accompany any storms. The cold front will ever so slowly work its way eastward across the region late tonight and tomorrow, shifting winds around to the northwest. This will develop upslope MVFR/IFR conditions west of the Blue Ridge with a trend to VFR conditions east. Expect enough wind flow to keep fog formation in check but low level moisture is abundant and cigs west of the Ridge will likely be lower than typical upslope and expect some sprinkles/drizzle as well, especially at KBLF. Any subtle changes in timing will complicate fog/stratus forecast tonight so this will be monitored closely and confidence is medium to low. Conditions will trend upward after daybreak tomorrow. The low level wind field will amplify and start some gusty conditions along the hilltops overnight. Expect steep low level lapse rates to yield a well mixed boundary layer and allow low level winds to mix down and make for some gusty conditions all locations through Wednesday afternoon. Instability appears tall and skinny on model soundings tomorrow but lapse rates are steepening and will make for some isolated showers/thunder tomorrow afternoon, especially east of the Ridge. Expecting sparse coverage so will go with vicinity in TAFs. Extended Discussion... High pressure will be overhead by Thursday. VFR conditions are expected with this cooler and drier air mass through Friday. MVFR to IFR fog is possible for a few hours each night along and near the typical river valleys, especially west of the Blue Ridge. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...AL LONG TERM...AL AVIATION...MBS/RAB

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.