Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211413 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1013 AM EDT Mon May 21 2018 .SYNOPSIS... A southerly flow will continue to push warm and humid air into our region early this week. The nearly stationary front to our north will finally push south across our area mid to late week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1000 AM EDT Monday... Instabilities are increasing this morning and as the inversion breaks, showers and a few thunderstorms will pop up over the area by noon. Some showers have already started to form over the northwest North Carolina foothills. This afternoon numerous showers are expected south of hwy 460, then will spread northward late this afternoon into this evening. PWATS values from this morning`s soundings range from 1.00 to 1.40 inches. Steering currents are also weak. Slow moving showers and thunderstorms are expected and will have the capability to produce heavy downpours. Due to the sporadic natures of where the heavy rain will occur, no Flash Flood Watches are expected at this time. This may change this afternoon as we get a better handle on where storms form, especially over areas that have seen rain in the past 24-36 hours. As of 245 AM EDT Monday... High ground moisture from the rain the past 5 to 7 days allowing for fog formation along valleys this morning, with only some cirrus at times overhead. Will see patchy dense fog as well, but not expecting enough coverage for an advisory. Forecast centers around the next piece of upper energy that is over southwest GA and Florida panhandle this morning, and its northward progress into our forecast area this afternoon, interacting with a frontal boundary that will be stretching from Illinois to the Shenandoah Valley. The morning looks mainly dry with sunshine giving way to increasing clouds in the south. High-resolution convective allowing models start to initiate storms over the higher terrain of the NC mountains and far southwest Virginia around noon, then show some concentration of activity spreading northward into southeast WV and the New River Valley by mid afternoon, with a secondary area stretching east-west from the NC Triangle area to the Triad/foothills. Storm motion will be weak around 10 kts or less, and with low level winds from the northeast and winds around 850-700 from the west southwest, we may see some anchoring/training at times, with slow propagation to the northeast. Given the nature of the pattern, with not a widespread coverage of storms, will not issue any flash flood watches at this time, but will have mention of flash flood threat in the HWO. Appears best location of heavier downpours will across southeast WV to the Mountain Empire of SW VA, the another from the southern Blue Ridge of VA into the NC foothills east into southside VA/NW NC piedmont where average amounts will be around one half inch, but storms with downpours as PWATS surge back toward 1.5 inches could put down 2 inches in an hour. As far as severe threat, model soundings suggest very moist layer with SBCAPEs around 1000 J/KG this afternoon. Cannot rule out some isolated wet microbursts but main threat is localized flash flooding. Muggy with highs in the mid to upper 70s mountains, to lower 80s in the piedmont/foothills. Tonight, the boundary of moisture convergence will shift northeast from the Greenbrier Valley to southside VA and weaken after midnight, while warm front lifts northward toward PA to the Delmarva. will keep some lingering showers late from the Alleghanys to the Lynchburg/Appomattox area and points north. July like temperatures continue for overnight lows, ranging from the lower 60s west, to mid to upper 60s east.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 320 AM EDT Monday... With plenty of low level moisture and light winds added patchy fog to ISC grids Tuesday morning. An upper ridge over Bermuda will continue to stretch westward into the Southeast Tuesday. A southwest flow will push warm unstable air into our region ahead of the cold front to our west. This will result in scattered showers and thunderstorms, with locally heavy rains. High temperatures on Tuesday will range from around 70 degrees in the mountains to the lower 80s in the piedmont. Convection will diminish Tuesday evening into Tuesday night with the loss of solar heating. Under mostly cloudy conditions, low temperatures Tuesday night will vary from the upper 50s to mid 60s. The upper ridge will sink south into Wednesday, losing its influence on the region. A weak front should move across the area Tuesday night into Wednesday. A weak upper level trough will draw Gulf and Atlantic moisture northward into the area Wednesday. This tropical moisture interacting with a frontal boundary will once again bring numerous showers and thunderstorms with heavy downpours Wednesday. Since the ground will remain wet and creeks, streams and rivers are elevated, there is a chance for renewed flooding by the middle of the week. High temperatures on Wednesday will feature readings from the lower 70s in the west to the mid 80 in the east. The cold front will move south into South Carolinas Wednesday night. High pressure will build southeast out of the Ohio valley into our region. Low temperatures Wednesday night will generally range from the lower 50s in the west to the mid 60s in the east. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 320 AM EDT Monday... High pressure will continue to wedge south on Thursday. This may be a good day for some of us to get some yard work completed. With a cool easterly wind, almost uniform temperatures are expected Thursday with highs in the upper 70s to lower 80s. This wedge of high pressure should keep most of the area dry Thursday night through Friday night. An upper level ridge over the Southeast states will expand northward on Friday. This ridge will bring warmer temperatures into the region for the weekend. The chances for thunderstorms return to our area on Saturday as a cold front approaches the region. The better chance for widespread showers and thunderstorms are expected Sunday and Monday as the front slowly crosses the area. Kept the good to likely pops created by the Forecast builder. It looks like for Tuesday, the better opportunity for convection will be in the west. In general, the unsettled weather will continue. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... As of 713 AM EDT Monday... Fog will lift at LWB/BCB in the 12-14z time frame with VFR through most of the daytime. Still looks like convection will fire south of BLF around 16z, then shift northeast thru southeast WV into the New River Valley by 20-21z, while another area unzips between HLX/MWK and RDU in the afternoon. Think all sites will see a better than 50 percent chance of rain, but will keep VCTS in instead of TSRA. Rain will be heavy at times and if core of cell passes over the airport, vsbys/cigs are likely to drop to IFR. Winds will stay light east-southeast outside thunderstorms. Storms will wind down this evening but showers could linger in the LWB-LYH corridor through 05-7z. Fog will form once again where it rains where higher confidence in IFR or lower residing at LWB after 08z. .Extended Aviation Discussion... Scattered MVFR showers and thunderstorms are possible Tuesday with another round likely Wednesday. Conditions are expected to improve later in the week. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...RCS/WP SHORT TERM...KK LONG TERM...KK AVIATION...AMS/WP

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