Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 271729 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 129 PM EDT Wed Jul 27 2016 .SYNOPSIS... A wavy front will be nearly stationary from the Mid Atlantic region to the mid Mississippi Valley through the end of the week. Weak impulses tracking along the front will combine with deep moisture to produce periodic rounds of showers and thunderstorms. The front will finally move well south of the area on Tuesday or Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1110 AM EDT Wednesday... Isolated showers late this morning near the Blue Ridge east of Fancy Gap, VA, with a few more showers in far SW VA. Models coming in initiating convection across the western forecast area by 18z/2pm, then shifting the storms east thru late afternoon. There is some disagreement in synoptic models somewhat with the 06z GFS hanging onto higher threat along/west of the Blue Ridge all day while the NAM and ECM shift some of the storms into the piedmont. The high-res models focus activity along the southern Blue Ridge, northwest toward Southern WV, and actually show the mountains keeping most of the activity through late afternoon. For now will have high chance pops cwa wide, higher in the west and north. The better dynamics with 25-30kt effective shear will stay in northern VA but should dip far enough south to increase threat of organized convection into southern VA. Still looking at highs from the mid to upper 80s west to lower to mid 90s east. Heat indices should stay under 105 so no advisory needed out east. Previous valid discussion... Precipitable water values range from 1.8 inches in the western county warning area to 2.0 inches in the extreme east. Storm motion will be southeast about 20 knots. Areas that had heavy rain on Tuesday will be more susceptible to flooding problems if there are storms again in the same locations today. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 400 AM EDT Wednesday... We are in for a continuation of unsettled weather as a shallow upper trof becomes established over the eastern part of the country through the weekend. This will allow a steady stream of short wave energy to move into the region from the southwest, while the upper jet provides diffluence to aid synoptic ascent. These factors will be combining with warm/humid/unstable air along a diffuse old frontal boundary lingering across the region. This all spells a good chance for showers and thunderstorms for the latter portion of the week and into the weekend. The variability among guidance solutions is still creating a good degree of uncertainty in timing/location, but the general consensus is for increasing shear to bring a severe threat to the area for Thursday afternoon into Friday, with a possibility for an organized MCS. High precipitable water values will also make excessive rainfall a threat, so hydro issues are a concern during this period as well. There is still much to be determined with this scenario so it warrants close attention in later model runs. Coverage of showers/storms looks considerable again for Saturday but with less shear and dynamic support so a more limited severe threat. Temperatures will continue to run a bit above normal with highs going from the mid 90s to lower 90s east of the Blue Ridge, and generally low/mid 80s to the west. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 130 PM EDT Tuesday... Overall pattern situation favors storminess every day but especially in the afternoon/evening. A frontal boundary situated from the Ohio Valley over to the Central Plains will slowly shift southeast into the Virginias and North Carolina over the weekend. Airmass will remain unstable and moist. Some issue with how far this front makes it as 5h ridge may be hard to break, but still looks like belt of westerlies will shift at least into our northern forecast area over the weekend. Highs will be seasonal with lows slightly above normal through most of the period. Highs will range from the lower to mid 80s mountains, to upper 80s to around 90 east. Lows will be in the lower to mid 60s mountains, to upper 60s to around 70 east. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 120 PM EDT Wednesday... Convection will again be problematic as we head through the afternoon. Radar at issuance time shows a cluster of storms heading toward BLF therefore put a tempo group for moderate thunder here from 18-19z. Otherwise will keep VCTS in for the afternoon and amend as necessary when storms near terminals. Storms will end/weaken this evening with fog developing overnight. Similar to this morning, fog will be dense at LWB and possibly BCB/BLF, with MVFR possible at the other sites. Another cluster of storms should form in the mountains around or after 18z Thursday so nothing added to the terminals before 18z. Extended aviation discussion... The upper ridge will remain just south of the area and a residual front nearby through Monday. This should allow for periodic daily convective coverage. Appears more widespread sub-VFR possible with thunderstorms later Thursday with a stronger wave along the front with perhaps some decrease in coverage by the weekend as this feature passes. At least diurnal MVFR/IFR possible each afternoon/evening through Monday for now. Late night and early morning fog will likely occur at the usual valley locations, and those chances increase across the entire region if any rain occurs during the afternoon or evening at any site.
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&& .CLIMATE... Record high temperatures for Wednesday (7/27) Roanoke.....103 in 1936 Lynchburg...103 in 1936 Danville....102 in 1952 Blacksburg...94 in 1993 Bluefield....89 in 1966 Record highs for July 28 Roanoke......104 in 1930 Lynchburg....103 in 1936 Danville.....102 in 1952 Blacksburg....95 in 1966 Bluefield.....90 in 2011 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/WP SHORT TERM...MBS LONG TERM...WP AVIATION...AMS/WP CLIMATE...PM

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