Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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303 FXUS62 KRAH 252038 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 438 PM EDT Thu May 25 2017 .SYNOPSIS...
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An upper level trough will move off the mid-Atlantic coast this evening. Weak high pressure will build into the Southeast on Friday and Friday night. A warm front will develop across the Appalachians and extend into North Carolina and Virginia through the weekend.
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&& .NEAR TERM /THROUGH FRIDAY/...
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As of 110 PM Thursday... A mid-upper low over western Appalachians is pivoting east southeast this afternoon. Cold air aloft associated with the upper low combined with solar heating is supporting convection in central North Carolina with small hail. Isolated stronger cells have the potential to produce up to 1 inch diameter hail. There will be a related conditional threat of severe hail, particularly east of U.S. Hwy 1, where both instability and SSWly mid level flow/bulk shear will be relatively maximized in a brief window from 17Z-21Z. Strong to damaging straight line winds, driven by both the background mid level flow and sub-cloud evaporational/diabatic cooling, may also result. After about 21Z, the passage of the trough axis will cause the mid level flow to weaken and veer and consequently mitigate an earlier severe threat, while small hail will remain possible through early evening. Lastly, mixed character precipitation (Ie. a stratiform shield of light rain with some convective elements) will likely pivot across the nrn piedmont as the parent mid level moist axis swings around the base and wrn side of the upper trough; and this may result in a few sprinkles there this evening, until the moist axis lifts away after 03Z. Lows tonight in the 50s, with a light but steady Swly breeze in the MSL pressure gradient between sub-1000 mb low pressure that will be lifting away from the Middle Atlantic coast, and incoming 1015 mb high pressure from the nrn GOM and Gulf coast. Ridging and drier airmass on Friday will support clear to scattered clouds with max temperatures 80 to 85.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
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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.
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&& .LONG TERM /Sunday through Thursday/...
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As of 430 PM Thursday... A ridge aloft across the northern Gulf of Mexico will shift east and off the Southeast coast by Wednesday and Thursday. A mid and upper level closed low over central Canada will slowly move southeast into the Great Lakes region by the middle of the week with a trough axis pushing east toward the coast. A weak cold front will approach the region late Sunday and drop into the region on Monday supporting scattered, mainly afternoon or evening convection. It will be muggy with highs will range in the mid 80s to near 80 both days with lows in mid 60s to lower 70s. Another cold front will approach the region on Tuesday, move across the region on Wednesday and linger around the area on Thursday. This should result in a trend toward slightly cooler and less humid conditions as we head toward the middle of the work week. Scattered storms expected on Tuesday afternoon and evening will lead to drier conditions on Wednesday and perhaps Thursday too. Highs will range in the lower to mid 80s with lows in the 60s.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... As of 110 PM Thursday... Convection continues to intensify at 17Z from Albemarle to Chapel Hill to Roxboro. Isolated hail up to 1 inch diameter with stronger cells. Convective cells moving east northeast at 25 knots and will pass through RDU vicinity 1745-1830Z. Afternoon solar heating will support additional convection mainly northern half of area as an upper level trough and associated very cold temperatures aloft pivot northeastward across the forecast area. Outlook: At least a couple of clusters of showers and storms, some strong to severe, and with gusty outflow winds surging well away from them, will return to portions of central and/or northern NC for Sat afternoon through Sunday. The approach and stall of a couple of cold fronts east of the Appalachians may result in a band of MVFR ceilings over central NC Mon night, and also a small chance of diurnal convection both Mon and Tue. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BLAES NEAR TERM...JF SHORT TERM...BLAES LONG TERM...BLAES AVIATION...JF

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