Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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937 FXUS62 KRAH 180750 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 245 AM EST Sat Nov 18 2017 .SYNOPSIS... Surface high pressure will move off the North Carolina coast early this morning, resulting in a warm and gusty southwest flow today. A cold front will sweep east across the area tonight. Chilly high pressure will return for Sunday through Tuesday. && .NEAR TERM /Today through tonight/... As of 235 AM Saturday... High pressure sitting over the eastern Carolinas early this morning is poised to shift east and offshore in the next several hours followed by warm front passage, initiating a strengthening low level southwest flow that will dominate the day`s weather. Increasing and deepening moisture advection will lead to thickening and lowering high clouds, along with scattered stratocu (especially over the western CWA). Based on latest high res model guidance and on upstream conditions SE of the warm front, sustained winds will increase this morning to 12-15 kts, with periodic gusts to 20-25 kts, strongest across the NW and N CWA this morning as a 35-40 kt southwesterly 925 mb jetlet tracks from W NC into VA. Near normal thicknesses to start the day coupled with the warm air advection will push temps up to 63-71, coolest NW with thicker cloud cover. Then tonight, a quickly-moving band of showers is expected ahead of the cold front, which is expected to cross central NC 07z-12z. Forcing for ascent will be on the upswing this evening/tonight with a 130+ kt upper jet inducing improving upper divergence and weak DPVA aloft accompanying broad mid level trough passage (although the best DPVA heads to our north), but the overall lift will be modest, and CAPE will be absent. High PW advects in ahead of the front, with values well over 200% of normal in a narrow band which crosses the area tonight, and this combined with the quick shot of lift should bring about fairly high rain chances (mainly over the NW and N CWA) but with low QPF (a tenth of an inch or less) given the fast movement. SW flow will ramp back up after nightfall and remain strong and gusty overnight, as 925 mb winds strengthen to 40-50 kts, although not all of this will be realized at the surface, given the low level buoyancy ahead of the front. It is worth noting, though, that just behind the front, where we`ll still be well-mixed but with low level subsidence taking place, and with 925 mb winds still rather stout post-front at around 30 kts, we could see a period of higher gusts from the NW just behind the front. The coolest air will be delayed until after daybreak, and will stick with milder lows, ranging from the mid 40s NW to the mid 50s SE. -GIH && .SHORT TERM /Sunday through Sunday night/...
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As of 245 AM Saturday... Skies will be clearing early Sun morning, with the entire area expected to be clear by 15z as surface high pressure builds in from the west in conjunction with a trend to rising heights aloft behind the exiting mid level trough axis. The tight MSLP gradient between the departing cold front and incoming high will result in blustery surface winds from the NW, although not as strong as today`s and tonight`s SW winds. Expect sustained winds of 9-14 kts with gusts to 15-20 kts. Thicknesses should drop to around 20 m below normal, so despite the plentiful sunshine, highs will be cool, 53-62. We may see a brief resurgence in wind gusts Sun evening as one last mid level vorticity lobe drops through the region (strongest across our north and NE into VA), causing 925 mb winds to rebound to 25-35 kts especially over the NE CWA. Otherwise, though, winds will be diminishing Sun evening and night. Lows 27-32 with decent radiational cooling under clear skies. -GIH
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 200 PM Friday... Longer range forecast looking on track. A cold front will move east of the area early Sunday morning. Gradient between the parent low over Quebec and high pressure over lower Mississippi valley Sunday will lead to northwesterly surface winds gusting to 15-20 kts. Temperatures during this time frame should top out in the mid 50s with low temperatures near or slightly below freezing. A warming trend will begin on Tuesday as high pressure moves offshore and an upper level trough sits to the west of the region. On Wednesday the upper trough will pass mainly north of the area. With very limited moisture in place do not believe there will be much if any precip in the area. A dry cold front will move through Wednesday night bringing in a cooler airmass for the end of the work week. For Friday, low pressure will move out of the Gulf of Mexico and across the Florida peninsula spreading some rain northward into eastern and southern sections of our area. && .AVIATION /06Z Saturday through Wednesday/... As of 130 AM Saturday... VFR conditions will dominate at all central NC sites today, with the exception of the potential for a few hours of MVFR cigs 14z-17z this morning at INT/GSO. The bigger story will be the increasing winds from the SW this morning, peaking this afternoon with periodic gusts to 20-25 kts. There is a slight chance of low level wind shear this morning as a 35-40 kt jet from the SW near 2000 ft AGL. LLWS chances increase after 00z tonight as winds restrengthen from the SW around 2000 ft AGL to 40-50 kts. INT/GSO will see a trend to MVFR cigs and perhaps MVFR vsbys in showers very late in the TAF valid period (after 04z) ahead of a cold front approaching from the west. Looking beyond 06z Sat: A few hours of MVFR to IFR conditions in showers are expected late tonight as the cold front crosses the forecast area. VFR conditions will return after 08z at INT/GSO, after 10z at RDU, and after 11z at RWI/FAY, all with a drastic shift in winds from SW to NW as the front moves through. VFR conditions are likely Sunday through Tuesday as high pressure moves over the area. A storm system will develop over the Gulf Coast and approach our area Tue night/Wed, bringing possible sub-VFR conditions. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis/Franklin AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.