Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 180525 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 125 AM EDT Mon Sep 18 2017 .SYNOPSIS... High pressure will remain over the region this week resulting in mainly dry and mild weather over the next few days. Jose should track north, off the east coast Monday and Tuesday, before sliding just east of New England on Wednesday. && .NEAR TERM /THROUGH TODAY/... As of 1130 PM EDT Sunday... Isolated showers continue to fire up or linger from the Alleghanys south through the New River Valley and into the foothills of NC. High-res models continue this trend until about 3-4am then diminish it, but think showers fade a little sooner. Expect fog to be dependent on cloud cover overnight, with some clearing expected overnight. At the moment fog will be most likely in the New River to Greenbrier Valleys and patchy for the most part, except locally dense near rivers and where it rained this evening. No other changes to the forecast with lows in the mid to upper 50s west, to lower 60s east. Previous early evening discussion... No major changes needed with this update. Variable cloudiness early this evening with weak/relative surface high in place, cumulus cloudiness tending greatest toward the north and west. May see some decrease in cloudiness with loss of insolation toward mostly clear to partly cloudy skies. However some indication in some of the 18z solutions of a weak vort lobe aloft that may maintain or at least slow cloud burnoff. May even see some isolated nuisance showers until midnight in the southern Shenandoah and into the Roanoke Valleys, a trend reflected in the 21z HRRR/NAM-3km and the 12-km NAM. But these should be pretty harmless. Still looking at potential for patchy mist/fog overnight given radiation inversion with best chance in the Greenbrier and New River Valley. No changes to lows which appear on track. Previous near-term discussion issued at 300 PM follows... High pressure will remain in control of our weather this afternoon into Monday. An upper level shortwave will pass to our north this afternoon into tonight. NAM,RAP,Hiresw-arw-east,HRRR,GFS and ECMWF support the mention of isolated showers this afternoon into this evening across the north. The combinations of low level convergence and orographic lift may generate some isolated shallow convection this afternoon beneath dry air aloft. Kept pops trimmed below 30 percent, with the models generally overdoing pops and qpf recently. Hurricane Jose was at 31N and 71.9W at 15z and lift north in the Atlantic ocean. See latest NHC advisory. Any shallow convection will diminish quickly this evening with the loss of solar heating. Residual late day clouds will spread out into a leftover trapped strato-cu layer this evening into tonight, then clearing expected overnight. Light winds and low level moisture will create patchy fog especially in the western valleys. Low temperatures tonight will range from the mid 50s in the mountains to the lower 60s in the piedmont. The Eastern U.S. ridge will continue Monday with a subtle influence from Hurricane Jose as it moves northward just off the coast. Circulation around Jose may push some low level moisture into the region on northeasterly winds Monday, with enhanced convergence and orographic affects from the Blue Ridge westward yielding Isolated to widely scattered showers. High temperatures Monday will vary from the upper 60s in the west to the lower 80s in the east. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM EDT Sunday... Upper pattern amplifies over this time frame with a deep long wave trof developing over the western United States and ridging over the east. Future track of Hurricane Jose is very uncertain after Wednesday, with diverging solutions in the models. Monday night into Tuesday night winds will increase over the Virginia and North Carolina Piedmont, from the northeast then gradually from the northwest, in response to Hurricane Jose. This will result in downsloping in the foothills and Piedmont. Will trend toward warmer guidance for afternoon highs On Tuesday. Think high clouds from showers and thunderstorms upstream in the Plains and Mississippi Valley will only extend to the axis of the upper ridge axis and not get this far east. Will be left with low and mid level moisture trapped under the subsidence inversion. Cloud cover and any chance of precipitation will be especially limited on Tuesday when subsidence may be enhanced as this will be the time when Hurricane Jose is the closest to the region. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 1230 PM EDT Sunday... 500MB heights rise and upper ridge continues to build over the east through Friday. Seeing a small probability of precipitation on Monday along the southern Blue Ridge and foothills where there will be weak easterly upslope winds. No organized synoptic scale for precipitation through Sunday. Temperatures will remain at or just above normal. && .AVIATION /05Z MONDAY THROUGH FRIDAY/...
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As of 115 AM EDT Monday... VFR conditions look to linger a while longer as earlier showers along the Blue Ridge have all but faded leaving a swath of strato-cumulus including some mid deck in spots. Latest models again suggest that this trapped moisture should fade overnight but confidence remains low given degree of low level moisture that could again result in an expanding canopy of high end strato-cumulus through daybreak. Where skies do completely clear expect another round of sub-VFR fog to take shape over the next few hours with this becoming locally dense across the western valleys espcly around KLWB where IFR/LIFR likely by daybreak. A bit more uncertainty around KBLF/KBCB given light mixing over the ridges and more clouds near KBCB. For now will include a brief MVFR/IFR fog mention at KBLF late and IFR at KBCB where fog could advect in from the north/west despite clouds. Latest HREF solutions less aggressive in showing a lot of fog out east but appears some low cigs and/or vsbys could sneak in so including a period of sub-VFR at both KLYH/KDAN near dawn for now. Winds generally light and variable, mainly east to northeast from the Blue Ridge east and more west/northwest across the western locations overnight. Any morning fog/stratus should erode between 13-14z/9-10am Monday followed by overall VFR conditions. However may be a bit slower to clear given a bit more moisture around and better northeast flow developing across the east. This suggested with lower cigs off the latest Nam into early afternoon so something to watch. Could again see some isolated afternoon showers develop along the eastern side of the Blue Ridge and Appalachians. Left out of the TAFs attm due to low confidence and isolated nature. Winds light east to northeasterly overall but around 10 kts across the east Monday afternoon.. Extended Aviation Discussion... Overall persistence forecast to prevail for most of the upcoming week with strengthening high pressure remaining in place between Jose offshore and weak cold fronts approaching from the west. This should maintain good flying weather outside of early morning fog/stratus through late next week, with only isolated diurnal showers possible each afternoon.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/WP NEAR TERM...AL/KK/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...AL/JH/KK

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