Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 111931 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 231 PM EST Mon Dec 11 2017 .SYNOPSIS... High pressure will extend over the Gulf of Mexico and southeast states today through tonight. A cold front will cross North Carolina Tuesday, bringing much colder temperatures Tuesday night through Wednesday. && .NEAR TERM /THIS AFTERNOON AND TONIGHT/... As of 1120 AM Monday... Sunny skies were observed across all of NC late morning. The temperatures have become milder as the cold air mass continued to gradually modify. The only thing of note on the visible satellite data was the remaining snow cover that shows up across all the mountains and northwest part of NC, as far SE as the Piedmont Triad. Cloudiness associated with the next fast moving clipper type low was observed over the Ohio Valley. It will be very late today before the cloudiness increases over NW parts of the area. Highs should range in the lower to mid 50s, except upper 40s in the Triad where some of the sun`s energy continued to be used to melt the residual snow and ice. Attention turns to the potent mid level clipper diving SE over the Upper Midwest this morning. This wave, and its accompanying surface cold front, will drop SE then E into the mid Miss Valley and Ohio Valley through tonight. As it approaches, we`re likely to see increasing mid clouds tonight, especially across the NW and N, with weak moist upglide noted on the 310K surface. Improving low level moisture, especially over the NW CWA, may induce patchy stratus as well overnight. The trend to partly to mostly cloudy skies and the light SW breeze holding up overnight should temper cooling somewhat, yielding lows of 30-36, not far from normal but much milder than the last couple of nights. -GIH && .SHORT TERM /Tuesday through Tuesday night/... As of 310 AM Monday... The upper level shear axis and corresponding dry surface cold front will traverse the area Tuesday, arriving in the mid morning W, and shifting east of the area during the mid afternoon. Skies should remain partly to mostly cloudy through the morning, with a gradual improving trend to fair to partly cloudy skies in the afternoon, with a combination of thin mid and high clouds along with flat cu as moisture is trapped near the top of an increasing boundary layer mixed depth. The cooler air mass will be building in from the west, such that it appears that the mountains will initially block the coldest air, and we should still reach highs from the upper 40s NW to the mid 50s SE, although a stout breeze with frequent gusts around 20 kts will make it feel chillier, especially late in the day as the dewpoints plummet. While the initial cold front will be moving to our east by mid afternoon, the more prominent cold/dry air surge will arrive late Tue afternoon through the evening, as a strong vorticity max dives through the trough base across NC, with the dynamic trop dropping to around 650 mb. Some enhanced cloudiness and perhaps a burst of stronger wind gusts may accompany this trough passage. Otherwise, skies will clear out Tue night, and temps are expected to bottom out in the 20-25 range. These readings with a steady NW breeze will bring the wind chill down into the low teens over much of the area. -GIH && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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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 30s to low 40s.
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&& .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 25kt. Looking beyond Tuesday: VFR conditions will dominate through at least Thu night and possibly Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Badgett/Hartfield SHORT TERM...Hartfield LONG TERM...KC AVIATION...Badgett

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