Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300030 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 830 PM EDT Fri Jul 29 2016 .SYNOPSIS... Over the next several days, a series of disturbances will progress across our region, near or along a stalled frontal boundary. This interaction, along with the heating of the day, will continue to provide us with a forecast that has chances of showers and storms in it most days. Temperatures will be slightly above normal for this time of the year. && .NEAR TERM /THROUGH SATURDAY/... As of 830 PM EDT Friday... A shortwave trough along VA/NC Appalachian Divide continues to progress east. Deep convection associated with this feature has been moving east, but weakening. Per downslope westerly winds east of the divide, expect this activity to continue to weaken with mainly showers or isolated thundershower possible... the highest pops across the NC high country. On the backside of the shortwave, westerly winds will increase enough to maintain upslope low level cloud cover across the western portion of the area. Residual debris mid to high level cloud cover associated with the system will cover much of the rest of the skies across the area through Saturday morning. Low temperatures tonight will be comparable to those realized this morning. Expect low to mid 60s across the mountains with readings around 70 to the lower 70s across the Piedmont. On Saturday, yet another upper level disturbance will impact our region. The trajectory for this one will take a generous portion of it north of our area. However, enough of it will bring another round of scattered showers and storms to the area, especially in the afternoon. Coverage will be greatest across the northern third of the region. The Storm Prediction Center has updated its Day 2 Convective Outlook to include a marginal risk of severe weather across those areas of the forecast area generally along and north of the Roanoke River, east of Roanoke, VA. High temperatures tomorrow will range from the low to mid 80s across the mountains to the upper 80s to around 90 across the Piedmont. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 300 PM EDT Friday... Mid-summer type pattern continues across the CONUS with main belt of the westerlies north of the Mid-Atlantic region. Low amplitude troughing develops across the eastern half of the U.S. with energy topping the mean western U.S. ridge and dropping southeast into the trough position. A fairly well-defined short-wave is currently forecast by model consensus to be lifting northeast toward New England Saturday night with the best chances for organized rainfall tracking along with it. Lingering showers and few storms are possible Saturday evening with slow clearing toward Sunday morning. Sunday looks to be somewhat drier as slightly drier dewpoints are forecast to filter into the region. The change will be subtle but perhaps noticeable as guidance shows mid-60s dewpoints across the mountains by Sunday morning compared to the upper 60s and low 70s of recent days. Highs Sunday will range from mid- to upper 80s mountains to low 90s piedmont with dewpoints drifting upward into upper 60s to low 70s...so still muggy. Scattered showers and thunderstorms again possible in the afternoon under diurnal heating and localized convergence but coverage should be less than on Saturday. Will maintain 30-40 pops in Sunday afternoon across most of the area during favored peak heating hours and diminishing as usual overnight. Slight cooling Monday as the frontal boundary slips to our south becoming stationary over the Carolina and h85 temps drop a few degrees into the 16-18C range from 18-20C on Sunday. Should yield highs mid-80s to low 90s with some low 80s possible far west. Still chances for scattered diurnal thunderstorms generally 20s and 30s pops with highest over the mountains due to differential heating. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 300 PM EST Friday... Extended range models (GFS/Euro) show upper trough over the northeast slowly lifting out on Tuesday with surface high pressure in control and generally dry conditions. Significant exception is 12z Canadian model which brings a strong short-wave across the central Appalachians late Monday into Tuesday with high chances for rainfall. Elected to discount that solution for now and go mostly dry on Tuesday with slightly lower humidity, could even see a few dewpoints under 60F in the western mountains and under 70F east, which may actually be noticeable. Temps generally seasonable for early August. Front drifts back toward the north on Wednesday with increasing pops and and humidity as heights begin to build aloft once again. With upper ridge and rising heights continuing to shift eastward Thursday and Friday should see warmer temps and higher humidities again with renewed pattern of scattered afternoon storms but nothing particularly organized. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 800 PM EDT Friday... A mix of MVFR and VFR ceilings can be expected overnight as a weak upper level shortwave ripples across the central appalachians. Scattered showers and/or isolated thunderstorm is possible mainly west of Blue Ridge. In the wake of the disturbance, a westerly flow will help maintain upslope IFR/MVFR ceilings along the west side of the Appalachians, impacting BLF/LWB. This low cloud layer is expected to lift to VFR by 14Z/10AM on Saturday. Patchy light IFR/MVFR fog is also possible late tonight into early Saturday morning for parts of the region. Extended aviation discussion... The region will remain in an active weather pattern into early next week. A nearly stationary frontal boundary will be across or near the region, all while a series of upper level disturbances moves along this feature through the area. By Wednesday the front may move south of the region enough to take the focus for additional showers and storms with it. VFR conditions are expected for most of the time. The exception will be temporary sub-VFR conditions under the heavier showers or thunderstorms, and during the night with patchy light fog and stratus cloud development over parts of the region. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS NEAR TERM...DS/PM SHORT TERM...PC LONG TERM...PC AVIATION...PM

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