Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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210 FXUS62 KRAH 101838 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 140 PM EST Sat Dec 10 2016 .SYNOPSIS... High pressure will settle overhead through tonight, then shift offshore Sunday. A warm front will push northward through the area Sunday night, and then a cold front will move through the region Monday night, before stalling out across the Carolinas through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 140 PM Saturday... Another quiet and cold night ahead as a portion of arctic high pressure slides across the Mid Atlantic region tonight. While the vast majority of the column is very stable and dry, areas of high level clouds from the mid Miss Valley will track within fast zonal steering flow eastward across VA and northern NC this evening into the overnight hours, yielding fair to briefly partly cloudy skies across the northern forecast area tonight. Some of these clouds may exhibit a period of orographic enhancement, although the moisture aloft may not be sufficient, and the upper level wind direction is a bit more westerly than is ideal. Otherwise, these high clouds should be mostly thin with limited coverage, and as such will have minimal impact on radiational cooling with otherwise mostly clear skies and very light winds. Lows 18-25, coldest in rural Piedmont areas. -GIH && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 300 AM Saturday... Sunday, sfc high will drift offshore, leading to a sly low level return flow regime by late in the afternoon. this flow, originating offshore of Georgia/South Carolina will increase the presence of low level moisture. This should result in the formation of a low level cloud deck, spreading over the south half of central NC prior to sunset. Isentropic upglide increases appreciably bu sunset which should lead to a few patches of light rain over sections of the Sandhills and southern coastal plain. This upglide increases Sunday night, leading to a better chance for patchy light rain and/or drizzle over roughly the eastern half of the forecast area. With the lift and moisture confined to the lowest 10k ft of the atmosphere, expect rainfall to be very light, totaling no more than a few hundredths. Max temperatures Sunday dependent on some degree of sunshine, especially across the northern counties. If thicker cloud cover occurs sooner than expected ( by mid day or early afternoon versus later afternoon), then high temps may end up being 3-4 degrees cooler than currently forecast. High temperatures Sunday mid 40s north to around 50 south. Sunday night, expect temps to cool initially after sunset. After midnight, should see temperatures stabilize or slowly rise as a low level sly jet strengthens overhead and low clouds become thicker. Low temperatures mid-upper 30s north to the lower 40s southeast. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 240 AM SATURDAY... The general upper level patter in the GFS and ECMWF are very similar, however there are continued differences between the two with respect to precipitation chances and timing. Monday to Wednesday: Monday, an upper level shortwave will traverse the Great Lakes while the associated cold front will approach central NC from the north or northwest. Southwest flow ahead of the front will result in warm advection into the area during the day. The result will be fairly mild/above normal highs in the mid 50s NW to mid 60s SE. The front is expected to get hung up in the vicinity of the NC/VA border Monday Night through Tuesday Night as the parent surface low moves away to the northeast. Meanwhile, a strengthening low aloft will move eastward through Central Canada, while the flow over the Eastern U.S. will become more zonal but slightly troughed. This will contribute to the stalled southward progression of the front. There is still a bit of uncertainty regarding the southward progression of the front and thus the temperatures, particularly across the north, during this time. As a result, confidence in temperatures is below average. Will hold off on moving the front through until late Wednesday or Wednesday night, which will result in gradually lowering highs in the mid 50s to around 60 degrees Tuesday to low to mid 50s Wednesday. Lows Monday and Tuesday nights will be similar, upper 30s north to mid 40s south. Wednesday Night through Saturday: As the aforementioned upper low strengthens and slides further to the east-southeast, over Southeast Canada by Wednesday Night, the trough over the Eastern U.S. will become more amplified. The cold front will finally push through Central NC Wednesday Night and subsequent high pressure will move through the OH valley and into New England through Friday and ridge southward into NC. Latest model runs indicate strong CAD setting up for Friday Night into Saturday. The problem comes Friday night as moisture advecting into the region in southwest flow aloft may result in some p-type issues. For now will keep precipitation chances just below slight until there is a bit more model consistency and agreement, however wintry precipitation is not out of the question at the end of the period. Temperatures through the extended will be below normal with highs in the low to mid 40s Thursday and Friday, potentially dropping into the mid 30s to low 40s for Saturday. Lows will generally be in the mid 20s to low 30s. && .AVIATION /18Z Saturday through Thursday/... As of 100 PM Saturday... High confidence in VFR conditions through at least 15z Sun. High pressure will settle over the region today into tonight, before shifting off the Mid Atlantic coast on Sunday. Deep dry air remains in place, and any clouds through daybreak Sunday will be very high (above 15,000 ft AGL) with unrestricted vsbys and light surface winds. Then, as a warm front begins to push northward into the region, MVFR clouds will start to spread into NC from south to north after about 15z. Cigs are expected to drop to MVFR at FAY near the very end of the TAF valid period, but cigs should stay VFR elsewhere through 18z Sun. Looking beyond 18z Sun, MVFR cigs will continue spreading northward through NC Sun afternoon. Cigs should then drop to IFR after sunset, with a good chance for low level wind shear developing after midnight, as 1500-1800 ft AGL winds will be from the SW at 35-40 kts but under 10 kts at the surface. Areas of light rain will also develop overnight, with period MVFR vsbys along with the IFR cigs, as the warm front stalls over the area. Unsettled sub-VFR conditions should dominate from Mon into Wed as the front stalls out over the Carolinas with weak waves of low pressure tracking along it, although the details on timing of such adverse conditions are highly uncertain. The front should finally push back well to our south early Thursday, with a trend back to VFR as high pressure pushes in from the north. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...WSS LONG TERM...KC AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.