Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240311 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1010 PM EST Tue Jan 23 2018 .SYNOPSIS...
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An area of high pressure and attendant seasonably cool air mass will build into and settle over the region Wednesday and Thursday.
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As of 1010 PM Tuesday... A secondary cold front, which marks the true density airmass change and easiest discernible by dewpoints falling into the 20s, has just recently pushed through the Triangle, and will continue to progress SE through the remainder of the forecast area over the next 3 to 4 hours. Meanwhile, winds have dropped off considerably, with only sporadic wind gusts into the teens being reported. Under clear skies, resultant CAA will govern overnight lows, ranging from lower 30s over the western Piedmont to mid/upper 30s across central and eastern areas.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... As of 250 PM Tuesday... Wednesday and Wednesday night, high pressure at the surface over the southern Plains will build east across the Deep South and into the Carolinas. Meanwhile, an upper level disturbance will drop sewd from the Great Lakes toward the Mid Atlantic. This system will cause patchy high level clouds to stream out ahead of it. Still, expect a decent display of sunshine Wednesday. Warming the low level atmosphere dry adiabatically to 900-875mb layer achieves afternoon temperatures in the low-mid 50s. The disturbance will pass to our north Wednesday evening. This feature will likely maintain light mixing at the surface through the early overnight hours. This mixing may aid to keep temperatures up a bit, until the sfc winds decouple close to dawn. Min temps generally 25-30 degrees. The sfc high builds/extends overhead Thursday, maintaining mostly clear skies. Warming the lower atmosphere dry adiabatically to 850- 825mb yields afternoon temperatures once again in the low-mid 50s. Another cool night Thursday night as the sfc high remains overhead or near the coast. Min temps mid-upper 20s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 215 PM Tuesday... Friday and Saturday: Rising heights are expected during the period as short wave ridging aloft builds into the region. Surface high pressure centered near the mid-Atlantic coast Friday morning will shift offshore allowing a strengthening southerly flow to develop. Mainly sunny skies with just some high clouds are expected on Friday. As the deep layer flow becomes more southwesterly, increasing moisture will lead to an increase of multiple cloud layers on Friday night and especially Saturday. Highs will range in the mid 50s to around 60 on Saturday with lows in the lower to mid 30s on Friday night. Highs on Saturday will warm into the lower to mid 60s on Saturday. Saturday night through Monday: The pattern becomes more active but uncertain for the the late weekend as a broad eastward advancing upper level trough reaches the Plain on Saturday. The trough will amplify as it moves into the Mississippi Valley Sunday morning and then continues east reaching the southern Appalachians on Monday morning. Deep layer moisture will increase with precipitable water values exceeding an inch by Sunday morning. While the broad pattern and features are generally consistent across the NWP suite, notable differences are apparent in the details. In general, the guidance has trended slower and more amplified. The operational EC has consistently been slower, deeper and wetter with the system as it impacts central NC than the GFS. The last couple runs of the GFS have trended toward the EC and a slower/more amplified pattern is supported by WPC. Given this, have leaned heavily upon the EC and the WPC guidance for forecast details. Have slowed PoPs and increased them with the greatest chance on Sunday afternoon. The developing surface way shifts offshore on Sunday night with the precipitation all over by Monday morning. WPC rainfall guidance suggests around three quarters of an inch of precipitation is possible, more to the north and west, less to the south and east. Quiet weather returns for later Monday and Tuesday as upper level heights begin to rise and surface high pressure builds into the area. Highs will range in the lower to mid 50s with lows generally in the upper 20s to lower 30s. -Blaes && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 615 PM Tuesday... VFR+ conditions have returned to all TAF sites, with improving aviation conditions expected over the remainder of the period. Gusty westerly winds will continue to diminish during the early part of the overnight hours, with mostly clear skies expected to persist into Wednesday evening. High confidence during this period of the forecast. High pressure will build into the region tonight and settle overhead late Wednesday into Thursday, continuing the period of VFR parameters. VFR conditions expected to last through late Friday. There will be a chance for MVFR ceilings Saturday as an approaching cold front will induce a sly flow over the Carolinas. This flow will tap moisture from the Gulf and transport it nwd into our region, aiding to increase the cloud coverage. As the front gets closer Saturday night into Sunday, the threat for scattered showers and MVFR parameters will increase. && .RAH WATCHES/WARNINGS/ADVISORIES... && $$ SYNOPSIS...WSS NEAR TERM...CBL SHORT TERM...WSS LONG TERM...BLAES AVIATION...JJM/WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.