Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230740 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 340 AM EDT Thu Mar 23 2017 .SYNOPSIS... Continental polar high pressure will continue to modify over the Srn Middle Atlantic states through tonight. A warm front will retreat north across the region on Fri, as the high drifts east toward Bermuda. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 945 PM Wednesday... Forecast is on track. The opaque high clouds which covered the southern half of the forecast area for much of the afternoon have been shunted southward with the push of deep dry air into the area. Skies should remain clear for the next several hours, although high level moisture to our NW (evident on upstream soundings) should lead to increasing high clouds late, and these may be orographically enhanced yielding thicker cloud cover over the western CWA. Temps are running a degree or two warmer than the forecast pace, although as northeasterly surface winds die off later tonight, readings should plunge given the low dewpoints and expectation of good radiational cooling. Lows in the upper 20s to lower 30s. -GIH Earlier discussion from 250 pm: An upper level ridge over the central U.S. and a l/w trough along the eastern seaboard will funnel cold dry air into central NC tonight. This drier air already made evident by sfc dewpoints in the teens across the western Piedmont at 18Z. This drier air will continue to spread south and east through this evening. Orographic induced high clouds will slowly fade/dissipate through early evening as the atmosphere aloft dries out and the winds field weakens. Sfc winds will remain 4-8kts after sunset, though should decouple after midnight. With the cold dry air mass in place and near calm sfc winds, should see temperatures drop into the upper 20s- lower 30s overnight. Patchy frost possible in the well sheltered areas though most places will see little if any frost due to the dry low level air mass. && .SHORT TERM /6 AM THIS MORNING THROUGH TONIGHT/... As of 250 PM WEDNESDAY... Thursday, 850mb thermal trough overhead signals a day of well below normal temperatures. While skies will be sunny, the cold dry air mass deposited by the high pressure system will yield max temps in the low-mid 50s, a solid 10-12 degrees below normal. Thursday night, l/w trough will lift to the ne while the upper ridge will extend across our region. This set-up will maintain mostly clear skies and chilly overnight temperatures. Under clear skies and a light wind regime, temperatures will quickly fall after sunset with overnight temperatures generally near 30 to the lower 30s with the coldest temperatures across the far northeast Piedmont and the northern coastal plain. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 320 AM Thursday... The extended will primarily feature a Bermuda high and warm southerly flow, with highs in the 70s, at least 5-10 degrees above normal. Continued moistening Friday night may lead to some stratus near and west of the Yadkin River Saturday morning, and a pronounced cap will likely trap this moisture and yield partly to even mostly cloudy by Saturday afternoon. Meanwhile, and upper low over the Deep South will lift west of the mountains Saturday night, providing a glancing blow of DECENT height falls that should erode the cap and permit showers and storms, mainly west on Sunday. Current timing suggest early day clouds and showers, an extension of upstream convection on Saturday, may impede warming and destablization enough in the west to limit any severe with potential, though an axis of instability between the morning convection and the stronger cap to the east could support an isolated severe threat given 30-40kt bulk shear. The cold front associated with Sunday`s lifting upper low looks as though it will stay well west of the mountains and NC will stay in the warm sector, with another, less amplified system progged to cross the area on Tuesday. The latest ECMWF is much less amplified with this wave that it`s previous run, as well as the 00Z/23rd GFS runs. This system could be interesting given the potential for decent destablization in the warm sector on Tuesday and possibility of locally enhanced shear associated with the shortwave. For now, chance POPs still look most appropriate. After that, a backdoor cold front is forecast to sink south into NC by mid to late week, though the presence of the sub-tropical ridge makes frontal passage much less certain. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... As of 230 AM Thursday... Continental polar high pressure will result in VFR conditions through the TAF period. Surface winds around the high will generally be light and gradually veer from NEly/ENEly this morning to Ely/ESEly by this afternoon. The exception will be at FAY and RWI for a few hours mid to late morning, when winds may briefly increase to around 10-15 kts, with occasional gusts between 15-20 kts. Skies will be clear, aside from periods of thin cirrus. Outlook: There will be a chance of MVFR-IFR visibility restrictions in radiation fog in SErn NC (FAY and possibly RWI) Fri morning, then with patchy coverage throughout central NC Sat morning. A chance of showers and storms and sub-VFR conditions mainly at Piedmont TAF sites will follow for Sun. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...BADGETT NEAR TERM...HARTFIELD/WSS SHORT TERM...WSS LONG TERM...SMITH AVIATION...MWS

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