Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 260225 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1025 PM EDT Mon Jul 25 2016 .SYNOPSIS... Strong high pressure aloft will continue to result in hot and humid weather early this week. A weak cold front approaching from the north should bring increasing chances of showers and thunderstorms over the mountains into tonight, and across the region on Tuesday. This boundary looks to linger over the area through the rest of the week with added showers and storms possible each day. && .NEAR TERM /THROUGH TUESDAY/... AS of 1000 PM Monday... Heat Advisory in effect from noon to 8 pm EDT Tuesday for South Central Piedmont of Virginia. Widely scattered thunderstorms have been mainly confined to areas along and west of the Blue Ridge with forcing over the mountains providing just enough lift to trigger storm activity. Can`t rule out additional activity during the overnight, esp western slopes of the Appalachian Divide (Mt Rogers vicinity) where light westerly flow will continue to provide for weak low level convergence during the overnight. Overall intensity however, should wane per loss of daytime heating. Upper ridge will slowly weaken or flatten tonight into Tuesday as shortwave troughing passes to the north. Surface boundary sinks southward to just north of the area late tonight into Tuesday with the axis of higher pwats and weak lift strung out from the western slopes to across the north. This may result in convection linger especially across the north tonight. Otherwise, partly to mostly cloudy and very muggy expected tonight. Low temperatures tonight will range from the mid 60s in the mountains to the mid 70s in the Piedmont. The frontal boundary will drop south across our region on Tuesday. The combination of frontal ascent, orographic lift, and heating will result in scattered showers and thunderstorms especially during the afternoon. SPC in day two convection has portions of forecast area in marginal risk for damaging winds with convective clusters. High temperatures on Tuesday will range from the lower 80s in the mountains to the mid 90s in the Piedmont. Heat indices will climb as high as 105 degrees in the far east. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM EDT Monday... The upper level ridge will continue to sink south across the southeastern US through Thursday. Lowering heights means temperatures will be a little bit cooler each day. However, temperatures will remain above normal until we can get a cold front to pass over the region. Unfortunately, there is no frontal passages expected this week. Afternoon temperatures will run around 5F warmer than normal with 80s across the mountains and low to mid 90s east. Dew points will also remain elevated ranging from the mid 60s to lower 70s. Heat indices values will run 5F-8F warmer than the actual temperature. Some heat relief will come in the form of showers and thunderstorms each afternoon. Even though these storms may knock temperatures down, they will increase dew points keeping conditions very uncomfortable. The coverage of storms will increase each day and start earlier and end later. With zonal flow aloft, storms will start across the mountains by noon, then drift east over the piedmont during the evening hours. Forcing both Wednesday and Thursday is not ideal for widespread strong storms, however with zonal flow aloft, any waves rounding the ridge could change that. For now, we will continue to see a typical summer pattern with scattered afternoon and evening pulse storms. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 215 PM EDT Monday... The ridge of high pressure will drift off the southeast coast Friday, allowing an upper level trough to move over the Ohio and Tennessee Valleys Friday. Models develop a surface reflection along a lee trough that will bring an increase chance for strong to severe storms into the region. Models currently are placing the stronger dynamics Friday north of DC, but with all the instabilities, heat and moisture in the region, the chance for widespread severe weather will increase for the area Friday and/or Saturday. If we do not see widespread significant weather Friday, then Saturday will be the day. The upper level trough over the Ohio Valley strengthens Saturday and will push bulk of the energy east to the coast on Sunday. The upper level trough remains to our west Sunday and Monday, which keeps the chance for showers and thunderstorms in the area. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... As of 1000 PM EDT Monday... Ridging aloft will remain in place through tonight, with increasing low level convergence developing Tuesday over the mountains ahead of a weak cold front to the northwest. Given strong instability would expect greater coverage of storms Tuesday afternoon compared to the widely scattered activity Monday. Can`t rule out a stray storm overnight west of the Blue Ridge but threat as a whole will wane until daytime heating results in build-ups again Tuesday. Until then mainly VFR expected aside for some river valley fog or shallow ground fog for areas which received rain Monday. Any fog that does form will quickly disperse after sunrise. Medium to high confidence in ceilings, visibilities and winds during the taf period. Extended aviation discussion... The ridge will weaken through mid week as an initial cold front sinks toward the area from the northwest. This should bring about an increase in daily convective coverage Tuesday late afternoon and evening into Friday with periodic MVFR/IFR possible depending on exactly how far south the front makes it. 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 Tuesday (7/26) Roanoke.....101 in 1930 Lynchburg...104 in 1934 Danville.....99 in 2012 Blacksburg...94 in 1987 Bluefield....91 in 1993 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Heat Advisory from noon to 8 PM EDT Tuesday for VAZ046-047-058- 059. NC...None. WV...None. && $$ SYNOPSIS...RCS NEAR TERM...KK/PM SHORT TERM...RCS LONG TERM...RCS AVIATION...PM CLIMATE...PM

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