Area Forecast Discussion
Issued by NWS Blacksburg, VA

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113 FXUS61 KRNK 212325 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 725 PM EDT Thu Jul 21 2016 .SYNOPSIS... A Bermuda high will keep pushing warmer and more humid air into the region throughout the weekend and into the first part of next week. The combination of high air temperatures and humidity will create dangerously high heat index values, especially east of the Blue Ridge, with readings around 105 at times through the weekend. The heat and humidity will also create an unstable airmass, and a series of weak fronts moving through the region will help keep a chance for showers and thunderstorms in our forecast for the next several days. && .NEAR TERM /THROUGH FRIDAY/...
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As of 710 PM EDT Thursday... Just not getting any good Cu development late this afternoon into early evening. High res models continue to harp on showers forming along/near Blue Ridge but aside from one very brief shower near Boone around 6pm, its been dry, with better activity further south toward the NC/SC border west of Charlotte. For now just have isolated pops in this evening near the Blue Ridge similar to previous forecast. May need to increase sky cover as Cirrostratus becoming dense over the area. No other changes need at this time. Previous afternoon discussion... Satellite/radar indicate essentially nothing in the way of shower activity across the region this afternoon, and only noted one or two isolated showers earlier across the piedmont which quickly dissipated. However the cumulus field still shows orographic forcing along the Blue Ridge with a pool of instability just to the east. this will keep some slight chance pops for a stray shower across the southern Blue Ridge/foothills from VA into NC into this evening, then dry everywhere for the rest of the overnight period. There will be a little cirrus blowoff from convective activity well upstream in the Great Lakes/Ohio valley heading in our direction, but the overall synoptic pattern with light winds and no significant coverage of lower clouds will result in good radiational cooling once again tonight with lows just a degree or two warmer than last night. Also expect some valley fog to develop west of the Blue Ridge. Any fog/stratus will burn off Friday morning, then we can expect some more isolated showers/thunder to develop thanks to diurnal heating and orographic effects primarily be along and west of the Blue Ridge. However convection will get a bit of a boost late in the day thanks to a weak front approaching from the northwest and this may increase coverage in the west late in the day. With high pressure off the coast and front upstream, southerly winds will allow temperatures will begin their upward surge tomorrow and we can expect highs in the middle 90s east of the Ridge with mid/upper 80s west.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 PM EDT Thursday... The heat is on is the main weather story for this period. The strong upper ridge over the central U.S. will gradually shift west during the weekend. This will result in a better for a better opportunity for a cold front to move into the area and then stall over the region by Sunday night. Any isolated diurnal convection sparked by orographical influences along and near the crest of the Blue Ridge will dissipate quickly with the loss of solar heating Friday evening. There is a small chance that some of the convection associated with the cold front to our north may sag south into our area late Friday night into Saturday morning. In any case, it is going to be another night for the AC with readings from the mid 60s in the mountains to around 70 degrees. Coverage of showers and thunderstorms will increase Saturday ahead of the cold front. High temperatures on Saturday will climb into the mid 80s in the mountains to the mid 90s in the Piedmont. Heat index values will top the century mark across portion of the Piedmont. Another humid night expected Saturday night into Sunday morning, low temperatures will vary from the mid 60s in the west to the lower 70s in the east. Hazy, hot and humid weather anticipated for Sunday as 850mb temperatures climb to around 22 C by Sunday afternoon. A few mountains locations may see cooling showers or thunderstorms. High temperatures will range from the the mid and upper 80s in the mountains to the low to mid 90s across the Piedmont. Heat index values will once again top the century mark Sunday afternoon across the southeastern portion of our forecast area. Will mention the heat in the HWO for the weekend. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 330 PM EDT Thursday... The large upper ridge will extend from the West coast to the East coast through Wednesday. In the northern stream, a shortwave will drop southeast out of eastern Canada and crosses through New England on Tuesday. A frontal boundary will settle across the Mid- Atlantic and Southeast Wednesday into Thursday. Moisture will slowly increase Monday and Tuesday ahead of the front. Afternoon and evening showers and thunderstorms are possible Monday into Midweek. There remain disagreement in model solutions with just how far south the front will make it. This makes it harder to place the best time convection. Temperatures will be above normal for the start of the week and return to normal by end of the week. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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As of 720 PM EDT Thursday... High confidence forecast to keep it dry and VFR most of the period at all terminals. Cirrostratus canopy may hamper fog development overnight, but most models do not even show the high clouds out there now and on the NAM has some cloud cover overnight. Will trend fog to be less dense at LWB and add a tempo group for 1/2sm. Any fog/stratus will burn off Friday morning and leave SCT/BKN cirrus. Any diurnal convection would be isolated and mainly south of BCB/ROA toward GEV/TNB. Extended aviation discussion... Strong high pressure aloft centered across the Midwest will attempt to build eastward into the weekend, then retreat back to the west early next week. Our region will remain on the eastern periphery of the upper high and thus subject to weak disturbances in northwest flow aloft tracking around the Great Lakes and into the Mid-Atlantic. Moisture and instability will be sufficient for isolated pop up thunderstorms, but a slightly better coverage will be possible by late Friday into Saturday with a weak front/short wave moving into the Mid-Atlantic with a better threat for convection early next week as another front moves into the area, stalls, and lingers over the region for several days. Hot and humid conditions east of the Blue Ridge this weekend which may impact density altitude. Late night and early morning fog will be possible at the usual sites almost every day.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS/WP SHORT TERM...KK LONG TERM...AMS/KK AVIATION...MBS/WP

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