Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 101750 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1250 PM EST Tue Jan 10 2017 .SYNOPSIS... Low pressure over the Mid Mississippi Valley will deepen and move northeast into the Great Lakes as high pressure moves off the southeast coast today. Another low will form in the Rockies on Wednesday which will track northeast through Thursday. This will result in milder temperatures and occasional rain for our area through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 1052 AM EST Tuesday... Installation of AWIPS OB16.4.1 software is completed this morning. Made some minor adjustments in temperatures and dew point temperatures for this morning. Patch of light precipitation pushing off to our north. Southwest flow around the high center will advect warm air into our region. This will result in most locations warming above freezing mark this afternoon. The winter weather advisory for black ice will be allow to expire as temperatures will be warming this afternoon. More changes later... As of 400 AM EST Tuesday... Mid and high clouds had filled in over much of the Mid Atlantic region overnight. Band of precipitation was crossing east through the Ohio Valley. The southern edge of this precipitation may just grave northern sections of Greenbrier and Bath counties this morning. Otherwise expecting dry but cloudy conditions across southwest Virginia, southeast West Virginia and northwest North Carolina this morning. Some sun may break through this afternoon. All the cloud cover will balance out the strong warm air advection occurring today. Increasingly strong southwest low level jet will raise 850MB temperatures today and tonight. The snowpack over southern Virginia and northern North Carolina will hold back maximum temperatures a few degrees, but highs across the area will still easily get above freezing today. Surface temperature trend will be non-diurnal overnight. As precipitation begins...there may be a brief period when evaporative cooling as the air mass saturated lowers temperatures but the overall trend will be steady or rising. Models fairly similar in arrival time of precipitation this evening. Latest RAP/HiResnmm and HiReswrf all bring the leading edge of the precipitation to the West Virginia/Virginia line between 00Z/7PM and 03Z/10PM. Still looks cold enough at the onset of the precipitation for freezing rain in the Alleghany Highlands and northern Greenbrier County. By 1AM temperatures across the area will be above freezing. Rain will spread southeast and continue for the rest of the night. Stayed close to WPC for expected amounts. Added fog in tonight where dew points rise above freezing over the snow cover. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 400 AM EST Tuesday... The quasi-zonal upper level pattern will transition to a split flow regime with a closed low sinking over the Baja peninsula and some weak southern stream ridging over the southeast, keeping the Appalachians and central mid Atlantic region in a warm and moist southwesterly flow aloft. This pattern will support temperatures trending to well above normal and keep some precipitation in our forecast through the end of the workweek. On Wednesday, the weak frontal boundary that pushed through the region Tuesday night will work back northward as a warm front with a good chance for rain. Temperatures will be quite tricky as precipitation and lingering snow cover will want to lock in some cool in-situ wedging as thickness values surge. Believe the best course of action is to shade high temperatures on Wednesday a bit below guidance and allow the situation to develop before making any further downward adjustment. Southwesterly low level flow will really start to amplify as we head in to Thursday. However, we will be in a pattern of warm air advection that will inhibit downward momentum transfer. This will keep strong gusts from reaching the lower elevations and preclude the need for a wind advisory, but winds will likely be blowing at a good clip along the ridges with some gusts approaching 40MPH Thursday afternoon. There looks to be some light sprinkley precipitation around on Thursday before more substantial precipitation arrives again west of the Blue Ridge late Thursday night as the lingering frontal boundary sinks back into the area and high pressure over New England wedges strongly down the east side of the Appalachians Friday night && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 1202 PM EST Monday... Pattern this period favors a strong upper ridge over the southeast, with deep upper trough and closed over the desert southwest, with more zonal flow across the northern U.S. This pattern favors stagnant weather for the most part and will see a frontal boundary situated at times near us to keep the area in more clouds with a threat of rain, though majority of the precip will be staying north and west of us. The precip will be all rain as temps rise to above normal levels. Saturday will be the coolest as surface high pushes wedge of cooler air southward to the southern Blue Ridge, but even then it looks to be near normal or slightly above with highs in the 40s to lower 50s. Beyond next Monday models are agreeing that the upper trough/low head east so still looking even more unsettled with better threat of showers, but some differences exist on how if at all the upper low breaks down. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As of 1250 PM EST Tuesday... High pressure will slide east this afternoon into tonight. VFR conditions will continue this afternoon, but will lower as the afternoon progresses. With a southwest flow, low level moisture increases this afternoon into tonight. Ceilings will drop to MVFR late this afternoon into this evening, then areas of IFR will develop overnight into Wednesday. Rain will spread into the area from the northwest after 00Z/7PM. Models showed similar timing with precipitation reaching KLWB between 00Z/7PM and 03Z/10PM. High confidence the rain will reach KROA, KBCB and KLYH by 06Z/1AM. Ceilings will continue to lower to IFR levels as the rain begins. The precipitation may begin as freezing rain with some light icing possible in the Alleghany Highlands, including at KHSP, but as warm air is transported into the area on a strong southwest low level jet, temperatures will warm above freezing. The jet from the southwest peaks around 60 knots overnight. LLWS has been included at KROA, KLYH, KDAN and KBCB. Model soundings indicated the stronger wind would not mix down to the surface but medium confidence that KBLF will have wind gusts around 25 kts. Deeper moisture associated with this initial wave of rain should spill to the south Wednesday. MVFR/IFR conditions on Wednesday morning will improve by Wednesday afternoon. Medium confidence on ceilings,visibilities and winds during the taf period. Extended Aviation Discussion... Moisture returns back north Wednesday night ahead of a stronger frontal system and associated low pressure to the west. This likely to maintain areas of sub-VFR within lower cigs and patchy rain showers Wednesday evening into Wednesday night before seeing improvement back to VFR on Thursday ahead of the next front. This second frontal system will work its way into the region Friday into Saturday, maintaining the threat for additional sub- VFR in low cigs along with light rain and/or drizzle. Unsettled weather will continue into early next week.
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VA...None. NC...None. WV...None.
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&& $$ SYNOPSIS...AMS/KK NEAR TERM...AMS SHORT TERM...MBS LONG TERM...WP AVIATION...AMS/KK is the U.S. government's official web portal to all federal, state and local government web resources and services.