Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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676 FXUS62 KRAH 260718 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 315 AM EDT Fri May 26 2017 .SYNOPSIS... High pressure will extend across the Southeast states today into Saturday, as a weak trough extends down through western and central North Carolina. An upper level disturbance will cross the region late Saturday through Saturday night, followed by another disturbance Sunday afternoon. && .NEAR TERM /THROUGH FRIDAY/... As of 955 PM Thursday... A mid-upper low centered near the Mid-Atlantic coast will continue to lift northeastward and away from the area overnight. Given this along with the main trough axis now to the east of the area expect dry conditions for the rest of the night. Thus, expect clearing skies overnight with a cooler and drier air mass in place for tonight. Expect we will maintain a WSW to southwesterly breeze overnight as the mslp gradient should continue to remain somewhat tight. Given this expect temps will fall into the 50s overnight at most spots, with a few locations across the southeastern reaches of the area only bottoming out near 60. Ridging and drier airmass on Friday will support clear to scattered clouds with max temperatures 80 to 85. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 430 PM Thursday... The mid and upper level low over new England at the start of the period will depart as the upper level flow over the mid-Atlantic becomes more westerly Friday night as an upper level ridge develops across the northern Gulf of Mexico. Increasing mid and and high level moisture will result in some high cloudiness. Lows will range in the lower to mid 60s. A general westerly to west-northwesterly flow aloft is expected for Saturday and Saturday night across the mid-Atlantic. A good warm advection pattern will develop across the deep south and Southeast. This will result in the development of a warm front that extends from the southern Appalachians into the VA and NC and subsequent scattered convection. The best chance of thunderstorms will be across the northeast half of the CWA, primarily Saturday afternoon and evening. It will be noticeably warmer and a bit more humid with highs in the mid 80s to lower 90s across the southeast. Lows will range in the mid 60s to near 70. && .LONG TERM /Sunday through Thursday/...
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As of 315 AM Friday... Sun/Sun night: Tough forecast behind the MCV shifting off the Mid Atlantic coast late Sat night. Models indicate a weak shortwave ridge shifting over the area from the west, with a warm 850-700 mb layer, high clouds to limit insolation (likely convective debris clouds resulting from late-Sat storm complex over the mid Miss Valley), and weak mid level lapse rates during the first half of the day. Models show an eventual recovery of this air mass through the day, with low level warming and mixing allowing for late-day destabilization to 500-2000 J/kg of MUCAPE (highest SW, lowest NE) and deep layer shear of 45-50 kts. And an expected cluster of convection over TN early Sat may work with this destabilization to prompt organized storms over central NC late Sun, a development shared by the NAM/NAM Nest/GFS/ECMWF. After a mostly dry morning, will bring in scattered to numerous showers/storms late Sun into Sun evening. Highs 84-90. Convection chances should dwindle Sun night with models showing a batch of drier air between the exiting storms and well out ahead of the approaching mid level trough, which should feature strongly forced convection from the eastern Great Lakes through the mid/lower Miss Valley to TX. Warm lows of 66-72. Mon/Mon night: A mid level shear axis and accompanying cold front and convective band will approach from the W and NW Mon, as our steering flow gradually becomes more cyclonic as a deep mid level low wobbles eastward over southern Ontario. Deep layer shear and CAPE values are both expected to improve through Mon, especially along and east of Highway 1 where the GFS depicts 1500-2500 J/kg of MUCAPE and 40-50 kts of 0-6 km shear Mon afternoon. Will bring in high pops, especially central/east, during the day, trailing off late Mon night as the surface front pushes to coastal and SE NC. Thicknesses remain elevated above normals, favoring highs of 84-91. Lows 63-70 with some cooling in the NW behind the front. Tue-Thu: Mid level flow decreases and flattens a bit as heights rise over the St Lawrence Valley region, and with the diffuse surface front having settled near the eastern and southern edges of the CWA Tue and much lower PW advecting into the NW, will carry chance pops in the SE CWA only Tue. As the mid level trough axis shifts eastward through the Mid Atlantic and Northeast by early Wed, the below- normal PW and weak mid level lapse rates should continue to spread in from the west, and will have a dry forecast for Wed/Thu as weak surface high pressure builds over the region with rising heights and mid level subsidence dominating. Highs mostly in the lower to mid 80s, near seasonal normals. -GIH
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&& .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 220 AM Friday... Strong subsidence, behind the upper level trough and accompanying hail storms that crossed central NC on Thu, will result in VFR conditions through the 24 hour TAF period. SWly surface winds will be the primary aviation concern as they increase into the low to mid teens kts, with gusts around 20 kts, mainly between 14-20Z - highest east/at RWI. Outlook: At least a couple of clusters of showers and storms, some severe, will return to portions of central NC this weekend - one mainly over the northern half of the forecast area but with gusty outflow winds surging well away from them late Sat and early Sat night, then another on Sun. The approach and stall of a couple of cold fronts east of the Appalachians will result in a small chance of diurnal convection Mon and Tue afternoon. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...BSD/JF SHORT TERM...BLAES LONG TERM...Hartfield AVIATION...MWS

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