Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 160600 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 100 AM EST Sat Dec 16 2017 .SYNOPSIS... High pressure will move across the southeastern US through the weekend. && .NEAR TERM /TONIGHT/... As of 930 PM Friday... WV satellite and 00Z upr air data depict a nrn stream perturbation migrating enewd across wrn VA and NC, which has resulted in the ewd progression, and departure from cntl NC ,of the earlier mid-high level ceilings. This clearing trend will continue, with a steady ewd progression of the wrn edge of those ceilings fully out of cntl NC during the next few hours. Clear skies, in strong subsidence and height rises aloft centered over the upr Midwest and mid MS Valley -- in excess of 100-120 meters at 500 mb-- will follow for the overnight. At the surface, 1026 mb high pressure now-centered from the TX Gulf coast to wrn MS will expand newd tonight, behind a cold front that has just moved ssewd and offshore the sern NC coast in the past hour or two. Surface winds have already gone calm throughout much of cntl NC this evening; and any remaining nwly stirring should likewise subside overnight, as a portion of the aforementioned ridge "breaks off" over the Carolinas, separated by a sharp lee trough tucked tightly in the immediate lee of the Appalachians. As such, radiational cooling tonight should be strong, with associated low temperatures mostly in the middle 20s to around 30 degrees, though typically cooler sites like TTA and SCR, both of which were already down to 27-28 degrees at 02Z, may dip to near 20 degrees. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 153 PM Friday... Tranquil weather expected during this time with NW flow and mid/upr short wave ridging, and high pressure over the area. This will result in ample sunshine on Saturday. Skies will become partly cloudy Saturday night as high clouds move up into our area from the south. Forecast soundings and thickness profiles suggest subtle and gradual warming tomorrow. Highs Saturday from around 50 north of I- 85 to lower-mid 50s south. Lows Saturday night around freezing. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 250 PM Friday... A low amplitude ridge aloft will move over the area Sunday as surface high pressure shifts offshore. Ensuing southwesterly return flow will lift a warm front northward and across the area later in the day, and high temperatures will edge upwards to near normal, topping out mostly in the mid 50s. Moisture advection will be on the increase as well in the deep southwest flow, and cloudiness will spread over the area later in the day, with a weak front moving through Sunday night to produce mostly cloudy to cloudy skies and perhaps a few showers with lows falling to the lower 40s. The front will stall across the southern Gulf States Monday with the southern tail of the front over the northern Gulf of Mexico. There is a lot of uncertainty as to just how this set up will affect NC, as the latest ECMWF suppresses subsequent surface waves and associated showers south of the area through Tuesday night as it delays the eastward progression of a cutoff low over the 4 corners region. Meanwhile, the GFS is much more progressive with this `closed` cutoff low, moving it east and weakening it quickly as it tracks across the southern Plains and lifting the surface frontal zone northward to near the NC/SC border. This would produce better shower coverage Monday and Tuesday, especially across the southern tier of central NC. Highs Monday and Tuesday will be above normal, in the 60 to 65 range with morning lows in the 40s. Wednesday`s PoPs will be dependent upon which model has the evolution and track of the cutoff low pegged, as the ECMWF would produce at least chance PoPs on Wednesday as the low moves across the Tennessee Valley, while the GFS`s weakening low would already be out of the picture and we would be dry. Regardless, highs will be in the mid to upper 50s Wednesday, with similar high temperatures accompanying dry weather on Thursday and Friday. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... As of 100 AM Saturday... Through 00Z Sunday: High confidence that VFR conditions associated with surface high pressure over the area will persist through Sunday. Looking beyond 24 hours: A warm front lifting north into the area Sunday night and into Monday could bring a period of MVFR restrictions Sunday night and into the day on Monday. Lingering low- level moisture will continue to support periods of sub-VFR conditions, especially at KFAY through Tuesday night. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...np NEAR TERM...MWS SHORT TERM...np LONG TERM...mlm AVIATION...CBL

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