Area Forecast Discussion
Issued by NWS Blacksburg, VA

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887 FXUS61 KRNK 270544 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 144 AM EDT Wed Jul 27 2016 .SYNOPSIS... Lingering strong high pressure aloft over the Carolinas will result in hot and humid weather into at least mid week. A weak frontal boundary just north of the area should also continue to oscillate across the Mid-Atlantic region through the end of the week. Weak impulses riding along the front will combine with deep moisture to produce periodic rounds of showers and thunderstorms each day. && .NEAR TERM /THROUGH TODAY/... As of 1039 EDT Tuesday... Broken line of convection continues to slide southeast from Campbell County to Franklin County with core of high reflectivity the strongest near Brookneal. Atmosphere starting to stabilize some, but MLCAPEs remain at 1000-1500 J/KG across the southern half of the forecast area. The 18z NAM showed a progression of convection across the southern tier of the forecast area til 09z, so will lean pops higher from Southside VA/ NW NC Piedmont into the NC mountains and far SW VA overnight. Otherwise, expect skies to stay partly to mostly cloudy. Previous valid discussion... The strong upper ridge is weakening and will slide southeast Wednesday. Expect another very warm and muggy overnight with moisture and debris clouds. Low temperatures tonight will range from the mid 60s in the mountains to the mid 70s in the Piedmont. A weak surface front will stall across our region on Wednesday. Scattered showers and thunderstorms are expected Wednesday afternoon into Wednesday evening. SPC Day Two convection Outlook places eastern portions of forecast area in Marginal threat. The Shear is still not very impressive so the probability for widespread severe remains low. The main threat being pulse storms and any clusters that can organize due to outflow boundary interactions. High temperatures on Wednesday will range from around 80 degrees in the northwest mountains to the mid 90s in the Piedmont. Heat index may climb to near the century mark in eastern Piedmont, just short of heat advisory levels. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... As of 243 PM EDT Tuesday... Will start to see the strong upper ridge over the southeast break down this period as stronger upper wave moves across the Great Lakes. Models also overall in agreement in a stronger vort moving from the Mid Mississippi Valley Wednesday night into the eastern Ohio Valley by Thursday evening. This signal suggests an increased likelihood of storms with greatest coverage over the mountains Thursday. Therefore increase pops to likely along and west of the Blue Ridge for Thursday. There is good upper support with jet dynamics such that severe storms is possible if we get enough heating. However timing of complex may bring more clouds to the area Thursday morning limiting solar insolation. This wave shears to the mid Atlantic by Friday with 5h heights falling. Should maintain at least threat of storms Friday as frontal boundary starts to linger over the mid Atlantic. Question will be how far south this front makes it. We should start to see temperatures settle toward seasonal lat July norms by Friday but will remain sticky/humid. Highs Thursday will range from the lower to mid 80s west to lower 90s east. By Friday highs will be in the upper 70s to lower 80s west to around 90 east. && .LONG TERM /FRIDAY NIGHT 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 /06Z WEDNESDAY THROUGH SUNDAY/... As of 140 AM EDT Wednesday... Cluster of thunderstorms in southern Virginia was weakening as it moved east. Expect a few lingering showers at KDAN at the beginning of the TAF forecast period. The sky was clearing behind this line of showers and storms. Locations that had rain Tuesdayafternoon and evening will have MVFR to LIFR fog develop early this morning. Already seeing some LIFR visibilities in central and southern West Virginia. High confidence on the occurrence of LIFR fog at KLWB and MVFR at KLYH but lower confidence about the timing. Threat for storms again this Wednesday afternoon but for now will keep it VCTS until we see how storms organize. 00Z models were showing the mountains as the preferred location for storm development. Otherwise after fog burns off in the morning going to see VFR wx. Extended aviation discussion... The upper ridge will remain just south of the area and a residual front nearby through Sunday. This should allow for periodic daily convective coverage until the boundary either fades or sinks farther south. 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 Sunday 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. && .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 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...KK/WP SHORT TERM...WP LONG TERM...WP AVIATION...AMS/WP CLIMATE...PM

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