Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 200537 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1237 AM EST Sat Jan 20 2018 .SYNOPSIS...
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High pressure will drift across the southeastern United States through the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 930 PM Friday... Just minor updates required with this evening update, mainly matching up temperature trends which were slower than expected across portions of the Triad and a bit faster across the sandhills of North Carolina. Still some concern with isolated fog development tonight, especially across the sandhills where the surface dewpoint depression is only 5 degrees in spots. Confidence is low though, mainly due to the high overhead and the dry airmass aloft, so have continued to leave it out of the weather grids for now. Previous Valid Discussion... Deep westerly flow over the eastern U.S. coupled with a sfc high anchored over the Deep South will maintain a weak lee side trough over the Piedmont tonight. While sfc winds will likely decouple around sunset, this sfc feature should induce a weak south-sw flow over central NC overnight just above the surface. Thus, should see overnight temperatures a few degrees warmer. Some members of the NAM hinting at possible low cloud/fog development above the snowpack as warmer air just above the surface overrides the colder air at the surface. Will continue to monitor but believe tomorrow night may be a better set-up for low clouds/fog. Still expect to see a disparity between locations where snow covers the ground and where snow is absent. Minimum temperatures should range from 17-21 where the snow depth is several inches deep, to the mid-upper 20s elsewhere. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 235 PM Friday... The atmosphere will continue to warm as the deep wly persists and the sfc high remains positioned over Southern GA/north FL. The relatively dry air mass will continue to promote wide diurnal temperature swings from sub freezing early morning lows to mild afternoon temperatures. Under sunny skies, expect afternoon temps in the upper 50s to around 60. The exception will be where snow several inches deep remains. The snow pack of this depth will continue to have an influence on the air temps, so afternoon temps in the lower 50s will be more likely. Saturday night, a moistening atmosphere aloft coupled with a persistent low level warm air advection should promote the development of fog or low clouds late Saturday night/early Sunday morning, primarily across the Piedmont where recent heavy snow fell. If the fog does develop, areas of freezing fog may occur as early morning temperatures will be slightly below freezing. Min temps 29- 33. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 220 PM EDT Friday... Southern stream shortwave trough traversing the northeastern GOM and Florida Peninsula will provide little more in the way of some thin high clouds across central NC on Sunday. Meanwhile, sfc high over the SE US will eventually shift offshore Sunday night/early Monday. This will translate into a continuation of dry and moderating conditions, with highs Sunday afternoon ranging from mid/upper 50s NW to to lower/mid 60s SE. Milder min temps Sunday night as well, owing to strengthening southerly return flow and extensive high level cloud spreading east of the mountains, well downstream of the closed low and highly amplified trough advancing east through the nation`s mid-section. The closed low will track NE from the Upper MS Valley to SE Canada by Tuesday, which is coincident with the timing of the trailing cold frontal passage through the region. Models currently indicate a band of showers will accompany the frontal passage, but given how far removed central NC is from the better forcing, expect precipitation amounts to be on the light side, driven primarily by the WCB. Highs Monday, just ahead of the front, will be similar to Sunday`s mild temps, followed by a brief cool done behind the cold front Wednesday and Thursday. Temperatures will begin to moderate on Friday, with the approach of yet another amplified long wave trough advancing east into the Central US. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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As of 1235 AM Saturday... High pressure over the southeastern US will result in mainly VFR conditions through the weekend. The exception will be a good chance of fog and associated ceilings/visibility restrictions between 05Z- 14Z Sun, with some lingering sub-VFR ceilings possible through the midday hours on Sunday, as that moist layer lifts and disperses with diurnal heating. Outlook: Sub-VFR conditions, and showers, are expected to affect cntl NC along and ahead of a cold front Mon evening through early Tue.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...JJM/WSS SHORT TERM...WSS LONG TERM...CBL AVIATION...MWS is the U.S. government's official web portal to all federal, state and local government web resources and services.