Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 270108 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 908 PM EDT Fri Aug 26 2016 .SYNOPSIS... High pressure will be the dominant weather feature through the upcoming weekend, with just a chance for an afternoon shower or thunderstorm mainly along the Blue Ridge. A weak cold front may slowly slide southward into the area by the middle of next week and continue the chance for a shower or storm from the Blue Ridge westward. && .NEAR TERM /THROUGH SATURDAY/... As of 845 PM EDT Friday... Isolated shallow convection over far northeast sections finally fading out and should dissipate for the most part in the next hour or two given loss of heating. Still could see an additional isolated shower pop up elsewhere in spots between now and midnight per leftover instability/outflow, otherwise leaving it dry overnight. Guidance again showing some low level moisture under the inversion aloft rounding the ridge into eastern sections late but this scenario remains quite iffy. Think moisture more related to possible stratus/fog development as parameters off soundings even better for fog tonight so beefed up coverage by daybreak. Things remain very warm and muggy even after sunset with some temps still in the 80s and dewpoints in the 60s to mid 70s. Appears this will keep most eastern spots from dropping out of the 70s overnight with mainly mid/upper 60s mountains for lows. Previous discussion as of 325 PM EDT Friday... Expect any isolated showers or storms to dissipate this evening followed by quiet weather for the overnight period. Another round of valley fog looks like a good bet from the Blue Ridge westward toward daybreak. Lows tonight look to be just a bit warmer than last night with low/mid 70s in the east to low/mid 60s west. Warm upper ridge will remain in place over the region through Saturday. This will allow a large area of high pressure moving through eastern Canada to wedge down the eastern seaboard tomorrow. This will push a bit of a backdoor front into the area from the northeast and guidance suggest this will provide enough lift in the warm and humid airmass for a low chance for showers/thunder mainly for the southern Blue Ridge heading into the northwest mountains of North Carolina. Highs tomorrow will remain several degrees above normal with generally lower 90s east and mid/upper 80s to the west. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 325 PM EDT Friday... An upper level ridge will remain over the region through early next week. Expect strong subsidence under this ridge, which will push afternoon highs 5F-8F above normal with mid to upper 80s west and lower to mid 90s east. At this time, heat indices values do not approach triple digits, however with dew points in the upper 60s to lower 70s, very uncomfortable conditions are expected the next couple of days. Air quailty may be more of a danger, especially those with respiratory problems as winds will remain light and variable. Despite a strong ridge, diurnal heating and increasing PWATS may allow for a few storms to develop over the mountains each afternoon, but with almost no support aloft, any convection will be short-lived. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 325 PM EDT Friday... The upper level ridge over the region this weekend will retrograde to the west and be replaced by an upper level trough. Embedded short waves in this trough and a surface lee trough over the piedmont will increase the chances for afternoon and evening showers and thunderstorms. Areal showers may be moreso on Friday with a possible front passage. Models also continue to hint at a possible tropical disturbance in the vicinity of Florida next weekend. However, with an upper level trough along the east coast, the forecast track of this system should stay south of the area. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... As of 640 PM EDT Friday... Isolated convection across the southern Shenandoah Valley and northern Blue Ridge likely to persist with added cells popping up mainly east of KLWB and north of the KROA-KLYH corridor in the next hour or two before fading. Therefore leaving out any mention in the tafs pending release coverage/proximity. Otherwise high pressure to keep overall VFR in place overnight through Saturday. A shallow boundary/backdoor front will make a surge into the region from the northeast Saturday but do not believe coverage will warrant any mention in the TAFs as isolated/scattered convection will be centered on the southern Blue Ridge and likely very late in the day. Thus, the biggest concern will again be with low clouds/fog overnight given moist dewpoints and light winds. Again appears the greatest likelihood for MVFR/IFR conditions at KBCB with LIFR at KLWB. Guidance continues to suggest additional cloud cover along/east of the Blue Ridge late with trapped moisture under weak onshore flow. This still looks overdone so will only include a mention of MVFR at KDAN and KLYH toward daybreak. Lingering fog/stratus will burn off Saturday morning with VFR conditions into early Saturday afternoon under a scattered-broken 4-6 kft cumulus field. Should see a repeat Saturday night with any lingering evening convection fading after sunset followed by late night mainly valley sub-VFR in fog/stratus. Extended aviation discussion... A weak front will remain over parts of the area Sunday. Isolated to scattered diurnal showers and thunderstorms still possible into Sunday evening. Coverage will be limited in area and duration. Monday high pressure bubbles in but still a very humid airmass to keep isolated mountain storms around in the afternoon, but mainly VFR. Another front situated north of us Tuesday could enhance the convective threat, mainly over the mountains and north of ROA/LYH. Front should cross the region later Wednesday with possible sub- VFR at times in pre-frontal convection Wednesday afternoon. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...JH/MBS SHORT TERM...RCS LONG TERM...RCS AVIATION...JH/MBS/RAB

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