Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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039 FXUS62 KRAH 151951 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 250 PM EST Fri Dec 15 2017 .SYNOPSIS... High pressure will move across the southeastern US through the weekend. && .NEAR TERM /TONIGHT/... As of 153 PM Friday... As of 18Z, the sfc low was off the NE NC coast, and is on its way to the northeast. A trailing cold front extends from the Albemarle Sound southwest toward upstate SC. Low clouds north of the boundary (mainly along and north of the I-85 corridor) are beginning to break up as the front is starting to push south and drier air is moving in from the north. The boundary will continue shifting south as high pressure (that`s currently centered over the southern Plains) begins to build in from the west. As such, look for partly cloudy skies the rest of this afternoon and this evening with mostly high clouds persisting. The high clouds should also finally exit to our east later this evening and overnight as the upper short wave trough axis (currently located over the Ohio and Mississippi Valleys) crosses our area and moves east. The combination of mainly clear skies after midnight, diminishing winds (given the high that`s building in), and a cooler airmass behind the aforementioned front... overnight temps should run about 5 deg colder than last night...mid- upr 20s for lows. && .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/...
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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.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 1255 PM Friday... Through 18Z Saturday: Stratus and StratoCu with cigs aoa 2kft AGL are persisting north of the I-85 corridor, with VFR conditions farther south with mainly just cirrus. As the low off the coast of the Outer Banks exits northeastward later today, drier air will move in from the west, leaving mostly high clouds, even where sub-VFR conditions are occurring now. That`s expected to occur around 20 or 21Z. Thereafter VFR conditions are expected this evening, tonight, and Saturday morning through the end of the TAF period. After 18Z Saturday: VFR conditions expected through the rest of the weekend, then sub-VFR conditions possible early next week as moisture lifts north toward our area and interacts with an approaching cold front. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...np NEAR TERM...np SHORT TERM...np LONG TERM...mlm AVIATION...np

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