Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 112344 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 645 PM EST Mon Dec 11 2017 .SYNOPSIS... High pressure will move east tonight. A strong upper level disturbance and associated cold front will move east across the mid- Atlantic region Tuesday. Much colder conditions will follow for mid to late week. && .NEAR TERM /TONIGHT/...
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As of 645 PM Monday... Little change required to the near term forecast. Clear skies this evening will gradually become partly-mostly cloudy nw-se, primarily after midnight. The clouds will be in advance of a strong s/w and attendant sfc cold front approaching from the northwest. The approach of this system will induce a swly sfc flow to increase, again, mostly after midnight and focused mainly over the Piedmont. The stirring of the sfc wind and increasing cloud cover will likely cause temperatures to stabilize or inch upward overnight, mainly across the western Piedmont. Min temps will likely occur around midnight in the west. Lows will vary from the lower 30s in the normally colder locations to the mid and upper 30s elsewhere.
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&& .SHORT TERM / TUESDAY AND TUESDAY NIGHT/... As of 300 PM Monday... ...Gusty NW winds to 25-30 mph with wind chills in the 10-15 degree range Tuesday evening... The main cold front and upper level feature will move across central NC between 12z and 18z. This is when the mid and high level moisture will increase enough for variably cloudy skies. Once the cold front passes, winds will shift to the WSW and increase to 15-20 mph with gusts to 30 mph. CAA will be delayed a few hours behind the front due to the strong westerly downslope component. Guidance is robust in warming temperatures well into the mid 50s to lower 60s in the east, with highs 50-55 NW. Expect a very sharp drop in the temperatures late Tuesday and Tuesday evening with strong cold dry air advection. Readings will slip below freezing within a few hours of sunset in the Triad, and by late evening in the Triangle. Mainly clear skies and diminishing winds are expected late Tuesday night. Lows will be in the lower to mid 20s. Wind chill readings of 10-15 are likely from mid evening through the early morning hours. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 230 PM Monday... Cold air will be advecting into Central NC in northwest flow on Wednesday in the wake of the dry cold frontal passage. Despite full sun, highs will be capped in the mid 30s north to low 40s south. Overnight lows in the mid to upper 20s. Meanwhile, a shortwave will begin diving south-southeastward from central Canada, through the High Plains and toward the Mid-Atlantic. The resultant upper level winds will become briefly more westerly then southwesterly on Wednesday night. A reflection of this wave will be seen at the surface as a low moving through the OH Valley region, eastward to the Atlantic. The winds will become more southwesterly at the surface late Wednesday/Wednesday night ahead of the aforementioned low and its attendant cold front. This cold front, which won`t be as potent as the previous one, will stall over Central NC Thursday into Friday. A low strengthening along the stalled front over the area will result in an increase in temperature gradient from WV to SC on Friday. Persistent west-southwesterly flow into the region will result in increased warm, moist air advecting into the Carolinas and thus an increase in precipitation potential, mainly along and ahead of the front. The front should finally move eastward over the Atlantic late Friday into Saturday, allowing cold air to advect into the area from the northwest as high pressure migrates eastward along the Gulf coast, ridging into the Carolinas. Another frontal system develops in the Midwest Saturday/Sunday, approaching the Mid- Atlantic Sunday/Monday. Medium range models are in fairly good agreement for being so far out in time, so this may be a system of focus for the next week or so. Highs through Saturday will generally range from mid 40s to mid 50s, while lows will fluctuate between low to mid 30s and mid to upper 20s. Ahead of the next frontal system, temperatures will likely moderate, highs the mid 50s and lows into the mid && .AVIATION /18Z MONDAY THROUGH FRIDAY/... As of 1245 PM Monday... VFR conditions under high pressure will dominate through this afternoon and tonight. SW winds will increase tonight as the pressure gradient increases out ahead of the approaching front. This will lead to 8-12kt winds later tonight that mix to the surface. Some concern about SW winds 35-40kt aloft late tonight (2000-2500 AGL), but mixing should lead to 10kt wind at the surface precluding low level wind shear. We will continue to monitor. The cold front will move through dry on Tuesday. Winds will shift from SW to WNW and increase to 15-20kt after 18z, gusts to 28kt. Gusty winds will diminish Tuesday night after 09Z. Looking beyond Tuesday night: VFR conditions will dominate through at least Thu night and possibly Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...WSS SHORT TERM...Badgett LONG TERM...KC AVIATION...Badgett

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