Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 141506 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1006 AM EST Tue Nov 14 2017 .SYNOPSIS... Other than a fairly weak cold frontal passage Wednesday into Wednesday night, high pressure will keep our region on the dry side through much of the week. A more substantial cold frontal passage is expected for this upcoming weekend. Gusty winds and notably colder temperatures will follow it heading into early next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1000 AM EST Tuesday... As expected conditions are slow to improve this morning as a high pressure wedged down east of the mountains keeps abundant moisture trapped in the boundary layer. But the moisture and clouds will eventually lessen through this afternoon. Previous discussion... By the afternoon, mostly sunny skies will prevail after the inversion breaks and drier air begins to take over. High temperatures today will range from the mid to upper 40s across the mountains with low to mid 50s common across the Piedmont. Tonight, the ridge axis will continue to strengthen over the area, with dry air still working into the area from the northeast. Low level moisture will be more limited tonight as compared to this morning. However, we cannot rule out some pockets of patchy fog late tonight, especially within some of the mountain and river valleys. Low temperatures will range from around 30 to the lower 30s across the mountains to the lower 30s to mid 30s across the Piedmont.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 420 AM EST Tuesday... A series of short waves will continue to traverse the U.S. in a general zonal flow through the period. The main dynamic axis or storm track will be near the Canadian border through the week, but amplification of the upper-level pattern will lead more to a western U.S. trough eastern U.S. ridge by the weekend. The next in the week long series of upper troughs/short waves will arrive Wed night into Thursday. The main dynamics remain well to our north near the low center tracking across Southern Canada. This system will push a weak frontal boundary into the area that will stall to our south by Thu near the SC/NC border as the upper support lifts off to the northeast. This system will bring the next chance for light rain showers to the area. Rainfall amounts with this system are expected to be light, mostly 1/4 inch of less west of the Blue Ridge, with little to no rain east of the Blue Ridge. Very little of this activity may make it east of the Blue Ridge as the upper-level support wanes. Temperatures Wednesday will be a bit milder across the region than in recent days as the surface winds becomes southwest in advance of the front. Afternoon temperatures should recover into the 50s west of the Blue Ridge and into the 60s across the Piedmont. Short wave ridging will develop across the forecast area Thursday in advance of the next upper low moving southeast from south central Canada. Weak surface maritime-Pacific (mP) high pressure will drift across the under the upper ridge yielding a partly to mostly sunny day with mild temperatures. Thursday should for much of the CWA be the nicest, warmest day of the week once any lingering showers in the morning move out of the area. Friday should still be a decent day across the area as the Midwest system deepens and begins to approach from the west. However, associated clouds and precipitation are not expected to reach the forecast area until later on Saturday. Temperatures Friday will remain near to perhaps a few degrees above normal. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 126 PM EST Monday... Amplification of the upper-level pattern into the weekend and early next week will bring a strong weather system into the eastern U.S. over the weekend, lingering into early next week. Rapid surface cyclogenesis will take place across the Great Lakes as the upper trough deepens and moves into the area, then takes on a negative tilt later Saturday into Sunday. There remain notable differences in the timing of the front/trough into the eastern U.S. between the GFS and the ECMWF, with the GFS remaining a good 12-18 hours ahead of the ECMWF. These differences not only impact the timing of the associated precipitation, but more importantly the subsequent timing and degree of cold air that advects into the area Sunday into early next week. Massive differences are noted in the temperatures between the GFS and ECMWF MOS, with GFS high temperatures Sunday in the 30s near ECMWF MOS low temperatures for Sunday. This is evident in the 850mb temperature field as the bulk of the cold air with the ECMWF does not filter into the region until early next week, as opposed to the GFS which does so late Saturday into Sunday, with considerable warming noted by early next week. For now, have leaned toward a blend of various solutions as to not show preference too strongly for one model over the other. Nonetheless, there is a slight preference for the ECMWF timing over the GFS given the strength and deepening of the upper trough. Regardless of the exact timing of the models, a strongly forced line of showers (QLCS) is expected in advance of the front sometime on Saturday. Depending on how this unfolds will determine if any thunder is warranted. For now, using the Brooks-Craven SIG SVR values, thunder is not warranted, and even less likely than what was evidenced yesterday. Leading into next week, the general pattern among the GFS/Canadian/ECMWF is for a deep upper trough to be in place across the northeast U.S. into the first half of next week. This will lead to below to well below normal temperatures in the extended periods with lows in the 20s and highs in the 30s and 40s west to around 50 in the Piedmont. Precipitation will be below normal with a predominate drier northwest flow aloft, but the potential for upslope Alleghany snow showers certainly seems to be in place with 850mb temperatures hovering in the -8C to -12C range late in the weekend through early next week. Gusty northwest winds are expected behind the front with strong CAA/significant pressure rises, and deep low pressure developing across the Northeast. For areas along and west of the Blue Ridge, appears solidly in the Wind Advisory category, with the potential for a High Wind Warning at the higher elevations in northwest NC into southwest VA. Will continue to highlight this wind potential in the HWO/eHWO. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... As of 645 AM EST Tuesday... The center of surface high pressure will continue to progress eastward today. The axis of this high will advect southward along the lee of the Appalachians, with lingering low level moisture trapped under an inversion through much of the morning hours today. Most ceilings will be mainly VFR east of the crest of the Blue Ridge with a mix of IFR/MVFR across the mountains through the morning. By afternoon into tonight, drier air will continue to work its way into the region yielding a trend toward VFR conditions for most areas by the afternoon. Some patchy fog will return late Tuesday evening and during the overnight hours. Weak high pressure will drift across the area Wednesday keeping mostly VFR conditions in place. Extended Discussion... VFR conditions then continue until Wednesday evening, with a cold frontal passage. A period of sub-VFR conditions, brief showers and a west-northwest wind shift appear possible for the overnight period. Possible post-frontal sub-VFR ceilings into Thursday in the western Appalachians, otherwise VFR conditions. VFR then anticipated through Thursday evening. A cold front is expected to cross through the Mid Atlantic region Friday and Saturday with precipitation and strong winds both ahead of and behind the front. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS NEAR TERM...MBS/DS SHORT TERM...RAB LONG TERM...KK/RAB AVIATION...AMS/DS/MBS/RAB

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