Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 141847 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 145 PM EST Sun Jan 14 2018 .SYNOPSIS... Chilly high pressure will extend down into the Carolinas from the north through tonight. The high will retreat to our northeast Monday, bringing more seasonable temperatures to our region on Tuesday. A strong upper level trough will cross the region Tuesday night through Wednesday night. && .NEAR TERM /through Monday night/...
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As of 145 PM Sunday... Quiet, cold, and dry weather will hold through tonight, as the polar surface ridge noses into central NC, although we`ll face bouts of cloudiness as a couple of waves aloft cross the region within cyclonic southwesterly mid level flow. The first perturbation is a weak one, tracking northeastward into W NC, and this in conjunction with an increase in upper divergence associated with upper level acceleration over the Southeast will prompt some high cloudiness over the area tonight. A second, slightly stronger wave will cross the Gulf Coast region late tonight before emerging off the SC coast shortly before daybreak, and this will bring additional cloudiness into our far eastern sections later tonight. But overall, any clouds should be too thin/sparse and high to provide enough downward IR to counter the good radiational cooling conditions posed by the cold air mass and diminishing winds. Lows 12-21. The cool and dry weather will extend through Mon night. The aforementioned wave will track northeastward off the NC coast Mon morning into early afternoon, bringing a few added clouds across our east sections, but otherwise skies will be mostly sunny with just a few altocu. Thicknesses will begin to moderate as the high center pushes further away, and highs are expected to be a bit warmer but still well below normal, 37-45. Lows Mon night 19-24 under fair skies. -GIH
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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As of 300 AM Sunday... The initial inland sfc low associated with the high amplitude positive-tilted trough over the NE-central US will fill over the Eastern Great Lakes/NE US late Tuesday-Tuesday night, eventually giving way to a series of coastal low development along the Mid- Atlantic Coast Wednesday-Thursday as the potent upper trough assumes a neutral tilt as it pivots east across the region. There continues to be a large model spread WRT to the timing and strength/amplification of the trough and it`s associated ana-frontal precip band, driven by strong shortwave dynamics and f-gen that`s progged to move west-east across central NC late Tuesday night and into the day on Wednesday. Operational versions of the EC and GFS, have trended drier with liquid equivalent amounts over the past several runs. Meanwhile, the GEFS and EPS avg mean liquid QPF is generally around a 0.10" across much of the area, with slightly higher amounts of near 0.20" across the far northern/VA bordering counties. With afternoon temps on Tuesday expected to moderate into the 45 to 50 degree range Tuesday afternoon ahead of the attendant sfc cold front, current timing and thermal profiles, still supports precip starting as rain or a rain-snow mix at onset Tuesday night with west to east change-over to snow early Wednesday morning and into the afternoon(east)as the expansive Arctic High builds in from the west. As previous forecast discussions have noted, one model pitfall and potential forecast concern is that NWP models tend to advect low- level cold air east of the mountains too quickly, which in itself can be a self limiting process as considerable dry sub-cloud layers develop. Given continued high uncertainty, will make only minor changes to current forecast. Stay tune.
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&& .LONG TERM /Wednesday night through Sunday/...
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As of 210 PM Sunday... The Arctic blast is very strong but short-lived with H8 temps progged to crash to -12 to 13C Wednesday night as the parent high settles over the Gulf Coast region. Highs generally in the 30s both Wednesday and Thursday, with quick moderation as temperatures return above normal by the weekend.
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&& .AVIATION /18Z Sunday through Friday/... As of 100 PM Sunday... High confidence that VFR conditions will hold over central NC for the next 24 hours. Surface high pressure will continue to nose into central NC from the north, bringing stable and dry conditions. Passage of upper level disturbances will bring some high cloudiness (based above 15,000 ft AGL) across the area, mainly NW sections (INT/GSO) through tonight, with scattered lower (but still VFR) clouds over southern and eastern sections (FAY/RDU/RWI) late tonight through Mon. Surface winds from the NE will diminish tonight. Looking beyond 18z Mon, chilly high pressure will extend into the region through Mon afternoon before retreating to the NE Mon night, although VFR conditions will persist. Next chance for sub-VFR conditions will arrive late Tue through Wed as a potent upper level trough slowly crosses the region. VFR conditions will return for Thu/Fri as mild high pressure builds in from the west. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Hartfield SHORT TERM...WSS/CBL LONG TERM...CBL AVIATION...Hartfield

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