Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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085 FXUS62 KRAH 231843 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 243 PM EDT FRI SEP 23 2016 .SYNOPSIS... An upper level low and the remnant low from Julia will linger and weaken near the southern Carolina coast through Saturday. A cold front will drop south into the area late Saturday and stall south of the region on Sunday. A stronger cold front will push through the region late Tuesday or early Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 145 PM Friday... Quick update to account for a slightly faster erosion of clouds across the northern tier than expected. Mainly clear skies are now noted across Forsyth, Person, Granville, Vance and Warren Counties. Some breaks in the overcast have developed across much of the remainder of the area as well. Isolated to widely scattered showers have developed across the far southern Coastal Plain and Sandhills, these showers will continue to develop and push south during the afternoon. Current PoP and temperature trends looks good and need only minor adjustment. -Blaes Previous discussion from 1045 AM Friday...Latest surface analysis shows a the persistent remnant low from Julia located just south of Cape Fear. A weakening mid level vortex that was located across the eastern Carolinas was beginning to shear out and open up this morning. The air mass across the eastern Carolinas remains very moist with precipitable water values in excess of 1.9 inches in the southern coastal region and Coastal Plain. Notably drier air with PW values of 1.5 inches or less have reached the Richmond Va area and the western Triad. The latest visible satellite imagery shows a large region of almost exclusively low clouds across the eastern two thirds of NC with some breaks and thin spots in the overcast developing. Shower activity to the southeast of I-95 earlier this morning has diminished. NWP guidance is in generally agreement that drier air over VA and northwestern NC will push slowly south into central NC. Should continue to gradually see a lifting of ceilings and brightening of the sky this morning into this afternoon. Expect to see some breaks develop in the overcast, especially in a slightly divergent low level flow to the northwest of interstate 95 with the clouds more stubborn to the southeast of I-95. Convection allowing models develop scattered to widespread convection this afternoon across the coastal region, with more widely scattered convection in the RAH CWA across the southern Coastal Plain and Sandhills region with little chance of rain elsewhere. A weakly unstable air mass with thin CAPE should lead to a few thunderstorms as well, but given the weak flow severe weather is not expected but storms will be capable of producing locally heavy rain as the move slowly. Atypical highs are expected today with the warmest readings in the northwest including the Triad where there will be the most sun with the coolest conditions in the southeast with the more persistent cloud cover and scattered showers. Highs will range from the mid 80s northwest to lower 80s southeast. Skies will continue to clear this evening with the loss of heating and the arrival of drier air. With little forcing for ascent, no rain is expected overnight. Some clouds may persist across the southeast before areas of fog and perhaps some low stratus appear increasingly likely, most widespread from the northern Coastal Plain southwest across the remainder of the Coastal Plain into the Sandhills and eastern Piedmont. Lows tonight will range in the mid 60s northwest to near 780 southeast. -Blaes && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 255 AM Friday... Dry and very warm weather expected. Mid level ridging aloft continues to build in from the west, while at the surface, the weak trough drifts further offshore as weak high pressure moves in from the west, although lee troughing does form in the afternoon over the western Piedmont. With low PW and a fairly stable column, will keep pops under 15%, with mostly sunny skies. Thicknesses and statistical guidance indicate highs in the mid-upper 80s, around 6-10 degrees above normal. The anticipated backdoor front moving toward NC from the NNE is poised to move into the NE CWA Sat night into early Sun morning, driven by energy rotating around a large vortex centered near the Newfoundland/Quebec border. But this low does not appear to dig markedly down the East Coast, hinting that the front may not work very far into NC despite being propelled by a cool dense surface high to our north. The ECMWF tends to hold the front just north of the VA/NC border through daybreak Sunday, while the NAM/GFS dip the front into northern NC. Will lean toward the ECMWF solution and hold onto mild temps overnight, with lows Sat night in the mid- upper 60s and a minimal drop in dewpoints over the NE. Regardless of frontal progression, we are likely to see increasing clouds from NNE to SSW Sat night. While a few models generate shower activity ahead of or along the front over north central and NE NC Sat night, the presence of features to force ascent is uncertain, and will opt for dry weather for now and monitor trends. -GIH && .LONG TERM /SUNDAY THROUGH FRIDAY/...
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As of 243 PM Friday... The timing of the back-door cold front through the area on Sunday is still in question. The GFS and NAM are much quicker to blow the front south through the area late Saturday night/ear Sunday, while the ECMWF suggest the frontal boundary will tend to "hang up" or slow down across the forecast area on Sunday, which is very plausible given weak sfc pressure rises from the transitory parent high center retreating off the Northeast-Southern New England Coast. These models discrepancies are leading to lower than average forecaster confidence, making for a challenging temperature forecast on Sunday and likely setup a sharp temperature gradient across the area. For now will continue a "middle of the road approach" with highs ranging from mid 70s northeast to mid 80s southwest. Additionally, given the potential for the front invof the area, will continue isolated to slight chance chance pops. Mid/upper level ridge will build east over the area on Monday in advance of a closed low and upper trough progressing eastward into the Upper Great Lakes/Southern Canada. With the transitory parent high quickly moving off the Southern New England Coast, south- southeasterly return flow will quickly return to the area late Monday with rain chances generally restricted to upslope/differential heating over the higher terrain, while ridging aloft should keep the remainder of NC dry. SELY moisture advection and resultant weak isentropic upglide in advance of a cold front approaching from the west could produce showers across the area as early as Monday night/Tuesday morning with another round of showers and storms expected to accompany the frontal passage Tuesday afternoon/evening. Highs Monday and Tuesday slightly above normal with mild overnight lows in the 60s. In the wake of the cold front, high pressure will bring dry seasonable weather for the later half of the work week. Highs 75-80. Lows the 50s.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 155 PM Friday... A much drier air mass that is pushing into central NC has resulted in varying conditions across the area with VFR conditions near the VA border and Triad area to MVFR conditions with low ceilings and isolated showers to the southeast. The worst and most stubborn conditions are located across the southern Coastal Plain and Sandhills near the KFAY and KRWI terminals with ceilings around 1.5kft and widely scattered showers. Aviation conditions will continue to generally improve from north to south through the afternoon hours with most locations becoming VFR by late in the afternoon. Showers across the Southeast will decrease in coverage during the late afternoon. An isolated thunderstorm is possible but coverage and confidence precludes its mention in the TAF. VFR conditions are expected this evening with a scattered low cloud layer or two. Guidance suggests some fog will develop late tonight toward daybreak from the Coastal Plain south and west to the Sandhills. This will result in areas of MVFR to perhaps briefly IFR fog, most prominently near the KFAY and KRWI terminals perhaps extending to the KRDU terminal. Mainly clear skies with little fog is expected overnight at the Triad terminals of KGSO and KINT. Any fog or low cloudiness should quickly give way to VFR conditions by mid morning Saturday with a light mainly northerly wind. Looking beyond 18z Saturday morning, VFR conditions are expected on Saturday afternoon and evening before a cold front moves into the region from the north Saturday night. A period of adverse aviation conditions including reduced ceilings and visibilities in showers is possible beginning late Saturday night/Sunday morning and continuing through early Monday. Another period of adverse aviation conditions is possible late Monday into Tuesday as another cold front approaches the region. -Blaes && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES/HARTFIELD SHORT TERM...HARTFIELD LONG TERM...CBL AVIATION...BLAES

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