Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 030826 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 326 AM EST Sat Dec 3 2016 .SYNOPSIS... High pressure will build into the Carolinas from the northwest through Saturday night. A storm system will move from northern Mexico across Texas and the Gulf Coast states into the Southeast states Sunday through Tuesday, bringing unsettled weather for North Carolina. && .NEAR TERM /OVERNIGHT/... As of 855 PM Friday... Little change required to the near term forecast. Surface high pressure centered over the central Plains will continue to gradually drift east-southeast overnight into Saturday. This weather feature along with a dry wly flow aloft should maintain clear-mostly clear skies overnight across central NC. The dry air in place at the surface has allowed temps to drop into the 40s and upper 30s early this evening. The temps will stabilize overnight, resulting in min temperatures generally in the low-mid 30s, with upper 20s/around 30 in the well sheltered locations in the Piedmont. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 145 PM Friday... Timing of the approaching storm system that is expected to develop over Texas and the NW Gulf of Mexico is still expected Sunday night and Monday; however, as high pressure at the surface extends down the eastern seaboard later in the weekend, moisture will return from the Atlantic as a coastal front forms Saturday through Sunday. This means increasing clouds and chilly temperatures Saturday into Sunday. We will begin to increase the chance of light rain/drizzle with the coastal front to the SE on Sunday afternoon and night. Depending on how much precip falls, cold air damming (CAD) will most likely develop Sunday and linger as the system approaches early next week. We will trend POP up Sunday afternoon and night and trend temperatures down below guidance Sunday anticipating the development of CAD with the cool/dry air initially in place aiding in it`s development. Many Piedmont areas may stay in the 40s Sunday depending on timing of rain and CAD development. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 325 AM Saturday... Monday will be a transitional day with high pressure moving off the coast, a weak wave along the coast and new high pressure moving into the mid-Atlantic region from the Ohio Valley. The upshot of this is that we will move from more of an in-situ damming situation to more of a hybrid scenario but northeasterly winds across the area and chances for precipitation early in the day with a lull later on. The cold air damming should keep temperatures down around 50 degrees in the Triad with middle 50s across the southeast. Tuesday the Miller B scenario takes full effect a pair of lows on either side of the wedge parked over the Piedmont. Precipitation should begin early Tuesday morning and continue all the way through Tuesday night before the system starts to move off to the northeast. Accumulations for this event should be over an inch and possibly up to two inches. Temperatures will be tricky and dependent highly upon the track of the coastal low. With fairly high confidence, the Triad should stay cold throughout the day under the wedge with highs possibly only in the upper 40s. The bigger uncertainties in the temperature forecast lay in the south and east where highs could be as much as 60 degrees. Wednesday and Thursday will be dry and a little warmer on the front side of a longwave trough bisecting the continent. Highs in the 60s. By Thursday night, models begin to diverge on timing and available moisture leading to two very different possible scenarios for Thursday night into Friday. The GFS solution has a very progressive trough and a drier solution which brings very cold temperatures into the area on Thursday night. The ECMWF solution is slower and wetter which means warmer temperatures hanging around longer Thursday night. For now we are taking the dry, colder forecast so expect temperatures below freezing both Thursday and Friday nights with Friday being the coldest as very anomalous thickness values move into the area and bring low temperatures down into the 20-25 degree range. && .AVIATION /06Z Saturday through Wednesday/... As of 1255 AM Saturday... High confidence in VFR conditions for the next 24 hours. Surface high pressure will continue to build into the region today, with deep dry air as mid level ridging shifts over the Southeast states. Only a thin veil of high clouds is expected across the area today, although clouds will become more opaque with lowering bases to 12,000-18,000 ft AGL late today through midnight tonight as upper level perturbations emanating from the developing storm system over N Mexico track ENE toward the Carolinas. Surface winds will be light from the NW through daybreak, then from the NW around 8-10 kts through sundown, becoming light/variable once again tonight. Looking beyond 06z Sun: Mid clouds will continue to thicken and lower late tonight, dropping to 5,000-6,000 ft AGL by early Sunday, with light rain spreading in during the day Sunday from the SW as the upper level disturbances break down the mid level ridge. Confidence is high that conditions will deteriorate further to IFR Sunday evening/night and remain poor at IFR or LIFR into early Monday with periods of rain, particularly south. Some improvement to MVFR or even briefly VFR on Monday, but should quickly drop again to IFR/LIFR Monday night into Tuesday evening with rain areawide. Rain should taper off Tuesday night but IFR/LIFR conditions may hold through daybreak Wednesday, followed by improvement to VFR by midday Wednesday. The potential for low level wind shear will remain a concern, especially Sunday night and again on Tuesday. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...WSS SHORT TERM...Badgett LONG TERM...Ellis AVIATION...Hartfield

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