Area Forecast Discussion
Issued by NWS Blacksburg, VA

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531 FXUS61 KRNK 281731 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 131 PM EDT Wed Jun 28 2017 .SYNOPSIS... High pressure moves east to the coast this evening. Will start to see a return to the heat and humidity by Friday into the weekend. Our weather pattern may stay active into early next week as a frontal boundary stalls over or near the region. && .NEAR TERM /THROUGH TONIGHT/... As of 100 PM EDT Wednesday... Have made only minor adjustments to the forecast through the remainder of the afternoon. Have adjusted hourly temperature, dew point, wind, and sky cover forecast grids to reflect the latest observations and expected trends through the remainder of the afternoon. Very limited changes to the high temperatures were made with most areas left unchanged and a few spots adjusted by no more than plus or minus one or two degrees. As of 1000 AM EDT Wednesday... The river valley fog that formed early this morning over parts of the Greenbrier Valley and a few parts of the New River Valley, has dissipated. Sunny skies prevail across the region, and for the most part, that is how it will remain the throughout the day. The exception will be over parts of the Northern Mountains of North Carolina, northeast near the spine of the Blue Ridge to around Floyd County Virginia. This part of the area is more likely than other areas to experience some cumulus development, but still, the sky will still be mostly sunny in nature. Later today, western sections of the region may see some thin cirrus clouds invade the region from the west. But here too, mostly sunny, or even sunny, will be the best descriptor of the sky. Have made minor tweaks to hourly temperatures, dew points, sky cover and wind heading into the early afternoon hours based upon the latest observations and trends into the early afternoon. As of 300 AM EDT Wednesday... High pressure overhead this morning exits to the coast this evening. Still drier air will stick around to allow for another less humid day before we start to see dewpoints edging up late tonight. Aside from a few cirrus skies will be sunny today and clear tonight. Cannot rule out some river valley fog early this morning. A few cu not out of the question late this afternoon over the southwest mountains of VA into the NC high country. Going to experience a warm day but still around 5 to 8 degrees below normal with highs ranging from the mid to upper 70s across the mountains, to around 80-lower 80s east of the Blue Ridge. Tonight, southerly flow starts to increase on the west side of the high, mainly over the higher terrain while valleys stay light/calm winds. Should see temps a little milder than this morning but think the piedmont could actually sink into the 50s once again if the high slows down. 50s are likely in the mountains as well but should be about 5 to 10 degrees warmer than this morning. Valley to higher ridge temp difference could still be 10 degrees given increasing southerly flow allowing fog steep inversion Thursday morning. Also with light/calm winds again in the valleys, fog appears more likely, but still patchy in nature since we have dried out the past few days. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 314 AM EDT Wednesday... An upper level ridge builds over our area through Friday night, bringing a return to warmer and more humid conditions. The surface high continues to migrate east Thursday resulting in a southerly flow and the advection of moisture. While there is some modest recovery in PWAT values, forecast values are still expected to be 75- 100% of normal. The combination of solar heating, orographic lift and some low level moisture may create isolated to widely scattered showers and thunderstorms across the higher terrain of Northwest North Carolina Thursday afternoon. High temperatures Thursday will range from the mid 70s in the mountains to the mid 80s in the Piedmont. Moisture will continue to surge into our region Thursday night into Friday around the high center off the coast. Light winds and low level moisture may contribute to the development of some low clouds and patchy fog Thursday night, along with warmer temperatures. Low temperatures Thursday night into Friday morning will vary from the mid 50s in the mountains to the mid 60s in the Piedmont. A weak disturbance will push out of the western Gulf of Mexico and undercutting the upper ridge, moving toward our region on Friday. This weakness combined with increased instability and richer moisture could generate widely scattered to scattered thunderstorms Friday. High temperatures Friday will be near normal with readings from the upper 70s in the mountains to the upper 80s in the southeast. An isolated shower is possible in the west Friday night. It will be a mild night with temperatures from near 60 degrees in the west to around 70 degrees in the east. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 310 AM EDT Wednesday... During this period of the forecast, our region will be between a large upper ridge off the southeast U.S. coast and an upper trof that pushes east from the upper midwest Saturday, into eastern Canada into New England by Tuesday. This will result is series of upper level disturbances moving over area and keeping a daily chance of afternoon and evening showers and thunderstorms. The long range models all show differences in timing and strength of these systems, but the GFS appears to show slightly more run to run consistency, especially later in the long term period. The best chance for showers and storms during the long term period will be Saturday as a surge of higher PWAT air that the GEFS indicates in about 2 standard deviations above normal move into areas east of the Blue Ridge. The GFS and ECMWF indicate an upper level wave entering the west late on Saturday. By Sunday, there is modest agreement that a sfc boundary (likely not the true cold front) moves into our area bringing slightly drier air. Therefore kept lowest POPS on this day of the period. Monday into Wednesday, a low level south flow is re-established pushing up dew points/PWAT values/instability. All the long range models and ensembles hint that at least one upper level wave moves through sometime during this time which may result in slightly more organized convection Monday. With 850mb temps climbing to 1-2 standard deviations above normal late in the period (Monday-Wednesday), went a degree or two above guidance during this time. These temps combined with higher humidity levels will likely push heat index values at least into the mid 90s in the east for the first half of the week including the 4th of July. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 120 PM EDT Wednesday... VFR conditions are expected across the majority of the region through the 24 hour valid time of the 18Z/2PM TAFs. A bit more sub-VFR fog is expected late tonight into early Thursday morning as the center of high pressure shifts east, and weak southerly flow starts advecting more moisture back into the area. The area is expected to be precipitation-free also across most of the area. The exception may be isolated showers over the Northern Mountains of North Extended Aviation Discussion... Thursday afternoon, the area is expected to be precipitation- free also across most of the area. The exception may be isolated showers over the Northern Mountains of North Carolina, north into parts of Grayson Highlands of southwest Virginia. Friday, the flux of moisture into the region from the south will continue. Anticipate even better chances of showers and storms with localized, brief sub-VFR vsbys/cigs under the heavier cells. Friday night, the potential for IFR/MVFR fog will be greater, along with some areas with sub-VFR stratus formation. Saturday into Sunday, coverage of showers and storms increase with the approach and arrival of a cold front. Sub-VFR conditions will be more probable for a longer period of time, especially during the overnight hours. By Monday, the bulk of the precipitation will be south of the region. However, a wet surface and boundary layer will more easily prompt overnight fog and stratus. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/WP NEAR TERM...DS/WP SHORT TERM...KK LONG TERM...KK/PH AVIATION...DS

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