Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181511 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1010 AM EST Sat Feb 18 2017 .SYNOPSIS...
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An upper level trough will approach from the west today and cross the southeastern U.S. tonight through early Sunday. High pressure will build into our region behind the exiting low pressure system Sunday night and Monday.
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&& .NEAR TERM /today through tonight/...
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As of 1010 AM Saturday... Just minor adjustments this morning, mainly to reduce RH and speed up onset of light precip from the SW. The mid level shortwave ridge axis located overhead will shift steadily off the coast today as an upper low crosses the Mid Miss Valley and moves into the Mid South. Observed and high-res forecast soundings depict relatively little moisture with this feature below 700 mb, with weak to absent low level moisture transport and a light non-confluent SW flow. DPVA weakens as the low/trough approaches and dampens later today, contributing to reduced forcing for ascent. Large scale models continue to show no measurable precip in central NC, although the RAP, which has caught up with reality and is now doing a pretty good job, does rotate a band of decent showers from GA and upstate SC into our SW sections late this afternoon. Based on the limited low level moisture and lift but with a nod to high-res model trends, will have a slight chance of measurable showers over the far SW, with just sprinkles elsewhere, taking these sprinkles NE through the CWA as we head into the evening. Expect increasing clouds from the west today, with a trend to mostly cloudy areawide by nightfall. Rising thicknesses balanced with this increase in clouds favors highs in the upper 60s to lower 70s. Still-low dewpoints will translate to a min RH in the 20-30% range for much of the area. -GIH Earlier discussion from 255 AM: S/W ridge over the Carolinas early this morning will scoot quickly east and offshore in advance of an upper low pressure system that will cross the lower MS Valley today. Diffluent upper flow ahead of this system will result in increasing and thickening mid/upper level clouds later today, spreading sw-ne across the area. The arrival of this thicker cloud cover will play a role in how warm it will be this afternoon. Based on satellite trends, the broken/overcast skies will spread into our southern counties during the late morning/mid day hours, and over the northern counties during the afternoon. Thus, appears to be some potential for warming, especially across the northeast half of the forecast area. Will lean high temps toward the full sun values from the low level thickness scheme which favors highs in the upper 60sw- lower 70s, warmest along our eastern periphery. The low pressure system will be weakening as it approaches from the west. Thus, little if any moisture advection expected in the low levels which remain quite dry this afternoon. While some forcing noted aloft, any precipitation that develop will likely evaporate before reaching the surface. Thus have opted to mention a chance of sprinkles rather than slight/chance measurable rain. Variably cloudy skies and a threat for a few sprinkles will linger into tonight as the weakening upper level low passes overhead. The variably cloudy skies and light sfc wind regime will maintain relatively mild nighttime temps for mid-February. Overnight temperatures in the mid-upper 40s.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 255 AM Saturday... Our stretch of mild/warm temperatures will persist Sunday and Monday. The upper level low, which will reside overhead early Sunday, will depart by afternoon. Subsidence behind this system and developing nw flow in its wake will aid to diminish the cloud cover leading to mostly sunny skies during the afternoon. Considering the mild start to the day and the potential for increasing sun in the afternoon, temperatures should recover back into the upper 60s-lower 70s Sunday afternoon. An amplified upper ridge will extend from the eastern Gulf into the Great Lakes Monday. The resultant nw flow aloft will drive a dry sfc cold front across our region Monday afternoon. Warmer air ahead of this system will yield highs temps in the 70-75 degree range across much of central NC. The exception will be the far northeast where the earlier arrival of the sfc front may result in cooler temperatures in the upper 60s. Low level easterly flow Monday night may cause in patchy low-mid level clouds to form in the upslope region of the Foothills, possibly spilling into our far western Piedmont. Otherwise expect mostly clear skies Monday night. It should be slightly cooler with min temps in the 40-45 degree range. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 205 AM Saturday... The surface high that had been ridging into the region will lift off to the northeast on Tuesday, with a more southeasterly then southerly return flow setting up over Central NC by Wednesday morning as a subsequent warm front slides north through the area. Aloft, the ridge over the eastern U.S. will shift off the coast and weaken as the next weather system approaches. A closed low will break away from the northern stream trough late Tuesday, then slide slowly east-southeast over the Gulf of Mexico on Wednesday (well south of the North Carolina). Meanwhile, the northern stream energy will largely pass to the north of Central NC. Some light rain is possible over the area Wednesday/Wednesday Night, but accumulations should be minimal as the best moisture will be well south of the area. A better chance for descent rainfall will come Friday or Saturday a low pressure system develops over the northern high plains and progresses east. The parent low will track northeast through the Great Lakes as the attendant cold front extends south into the Gulf. The strongest warm advection into the Carolinas will be just ahead of the front Friday/Friday night, with the frontal passage on Saturday. Expect moderating temperatures through Friday Night (highs maxing out in the mid 70s Friday and lows in the low to mid 50s Friday Night), decreasing thereafter. && .AVIATION /12Z Saturday through Wednesday/... As of 645 AM Saturday... There is a high likelihood that VFR conditions will persist across central NC through 12Z Sunday. Mostly clear skies early this morning will give way to thickening mid-high level clouds this afternoon. Enough forcing aloft will cause some precip to develop, though the dry sub-cloud layer will cause most of the precipitation to evaporate before reaching the surface. Southwest surface winds will increase after 18Z Saturday to near 10kts with infrequent gusts between 15-18kts probable at KRDU, KRWI, and KFAY. Ceilings tonight will mostly vary between 7000-12000ft. Gradual clearing expected to occur Sunday morning-early afternoon as an area of low pressure pulls away from our region. Mostly clear skies anticipated Sunday night into Monday. There is a high probability of VFR conditions Monday through Tuesday. The approach of a low pressure system Tuesday night into Wednesday will increase the chance for sub-VFR ceilings. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Hartfield/WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.