Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230742 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 342 AM EDT Sun Jul 23 2017 .SYNOPSIS... A frontal boundary shifts south across our area through Monday, moving south into NC/TN by Tuesday. High pressure works from the Great Lakes into New York Tuesday into Wednesday, with previous front starting to drift back north as a warm front Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 304 AM EDT Saturday... Having to follow radar trends this morning, with some input from HRRR and RAP13. Looks like convective cluster over WV/KY will weaken as it moves eastward but will still bring thunderstorms and some moderate to heavy rain to portions of the WV mountains, southward toward the NC High Country. As this area moves east of the Alleghanys, expect to see weakening and/or dissipation. Sunday should be fairly active, but still some question on how much residual cloud cover there is with this mornings convections and influence on thermodynamics. Models are showing best concentration of convection fire up again from the Ohio Valley, eastward to the Alleghanys, but a little further south compared to Saturday as frontal boundary works a little closer plus density of cool pool with this mornings area of storms should set up leftover boundary across our CWA. The Storm Prediction Center, pretty much has slight risk of severe storms for most of our area, with main impact being damaging wind gusts. With some increase in mid level flow with 5h heights falling, should be decent setup for storms to fire. Again will be watching this mornings convection and seeing how cloud cover lingers if at all. Most models showing area of subsidence behind this mornings convection and vort allowing for clearing this afternoon along/east of I-81, so seems reasonable for strong to severe convection to form. At the moment have not had enough rain to warrant any flash flood watches. Not out of the question to see some repetitive clusters of storms which could lead to localized flooding this afternoon. As for pops, still confident on going above 50 percent later today, outside of likely to categorical pops before 8am in the mountains, but most areas should see 50/50 shot of having rain, with less coverage further southeast over the VA/NC piedmont. Highs today will be a degree to 5 degrees cooler than yesterday, especially west where thinking less sunshine overall. At the moment not achieving temps in the piedmont and dewpoints to have a heat advisory. Some locations are going to reach 100-104F, but appears higher heat index values stay further east/south over the urban areas of central VA and the NC Triad and Triangle. For tonight, sfc front still to our north and seems most models are favoring some lull in storm coverage behind this afternoons activity, however, enough agreement to keep better threat of storms in the west closer to higher theta-e ridging and moisture transport. Will side with drier wx overnight, with muggy temps continuing with lows in the mid to upper 60s west, to lower 70s east. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 325 AM EDT Sunday... Front looks like it stalls/slows over the forecast area Monday but deeper moisture slides further south. Going to see a little drier wx per most model solutions with a few showers/storms over the mountains, and across the southern CWA, though isolated convection seems plausible anywhere Monday. Staying very warm with a westerly flow increasing, but dewpoints start to drop some. Highs should range from the lower to mid 80s mountains, to lower to mid 90s east. By Monday night into Tuesday the axis of the upper trough slides east and shifts the frontal boundary further south. As this occurs, high pressure over the Great Lakes shifts east Tuesday afternoon into New York. Should see a shift in the winds from west/northwest to northeast. Some drying to take place but with southeast flow arriving on the backside of the front into the southern Appalachians, showers/storms may stick around in a scattered fashion over the High Country of NC into far Southwest Virginia, and possibly east toward Martinsville/Reidsville. Some noticeable change in dewpoints, but overall temperatures should run at or just above normal. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 1230 PM EDT Saturday... Passage of high pressure off the coast on Wednesday will bring cooler easterly windflow to the mid-Atlantic, resulting in likely the coolest afternoon temperatures of the week. Upslope wind flow will make for the best chances of shower/thunderstorm activity across the mountains. Winds will shift more southerly by Thursday, resulting in a return of warmer temperatures and higher humidity, and greater coverage of afternoon showers/storms, more so across the mountains. A cold front will slowly make its way across the mid Atlantic on Friday and Saturday, again resulting in scattered showers and thunderstorms both days, a few of which may become severe for brief periods of time. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... As of 115 AM EDT Sunday... Lots of uncertainty this period in placement of convection as models are all over the place. Confidence is the first 6 hrs of the taf cycle higher per radar trends which favors BLF/LWB to have a few showers, possibly thunderstorms around til 09-11z with better coverage BLF south toward VJI-TRI corridor by 12z. For today will be sticking with VFR and not having any fog outside convection, per increasing high clouds. Storms overall look to be potentially to be in a lull between 12-18z, awaiting heating and next upper disturbance to move in from the Ohio Valley ahead of a cold front in the afternoon. Overall looks like best organized activity will be in the LWB- LYH corridor and points north, though models also favor BLF and points west, while bringing an area of storms into far SW VA after 00z, with less coverage Danville until late in the period. Will keep token VCTS in all sites, as at least widely scattered coverage will occur in the afternoon, and will amend as necessary or hone in better toward the 18z tafs while monitoring radar. Winds will be SW-WSW through the period at speeds of 4-6kts overnight and 8-10kts after 14Z Sunday with low end gusts possible at most sites. Aviation Extended Discussion... The cold front currently to our north should be near the NC/VA border by Monday evening. This leaves a baroclinic zone in or near the area through much of the extended period. Additional upper- level disturbances are progged in northwest flow to impact the area, leaving an unsettled weather pattern in place. The most likely areas to see convection, at least during the first part of the week would be near the NC/VA border, mainly affecting KDAN. Late/night early morning fog can be expected in the usual locations, otherwise outside these concerns and scattered convection, mainly in the south, look for mostly VFR cigs/vsbys. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW/WP NEAR TERM...WP SHORT TERM...WP LONG TERM...NF AVIATION...RAB/WP

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