Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 052123 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 423 PM EST Mon Dec 5 2016 .SYNOPSIS... High pressure will build across the Middle Atlantic states through tonight, ahead of a Miller B low pressure system and associated cold air damming, which will result in the development and deepening of an area of low pressure through the eastern Carolinas on Tue. Another area of high pressure will build overhead for the middle of the week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 355 PM Monday... The weather will be quiet through early evening, as surface high pressure continues to ridge across the Middle Atlantic states. Clouds will then quickly thicken and lower, with light rain having already been observed at 21Z as far E as Wrn SC and SWrn NC, in association with a lead deamplifying perturbation now lifting across the Lower MS Valley. This light rain, from mid level ceilings, will overspread our region overnight, with temperatures expected to wet-bulb into the lower to middle 40s by daybreak.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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As of 415 PM Monday... WV imagery indicates the primary mid-upper low has already begun to lift more quickly across TX today, and this associated shortwave trough is forecast to pivot NEwd through the Central Appalachians Tue and reach the Chesapeake Bay region by 00Z Wed. Associated forcing for ascent will strengthen and deepen, the latter as isentropic upglide/WAA rapidly increase from S to N across central NC Tue morning. A few rumbles of thunder will be possible around midday, when both deep layer lift and lapse rates aloft become maximized with the passage of the shortwave trough and associated cold pool aloft. Widespread rain and overcast will result in cold air damming and temperatures that are likely to only rise a few degrees throughout the Piedmont, while a few 50s will be possible in the far S and E as a secondary low migrates through the Ern part of the state. The passage of the trough axis aloft will cause the widespread rain to end, and clearing to commence, from SW to NE throughout the afternoon and early evening hours. Storm total precipitation amounts are expected to range from three quarters of an inch to one inch. The clearing, in conjunction with wet soil, will then result in the development of patchy fog Tue night. Lows upper 30s to lower 40s.
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&& .LONG TERM /Wednesday through Monday/... As of 350 PM Monday... In the wake of the departing low pressure on Tuesday, and preceding a strong arctic front moving through the Midwest, the flow will be weak over central NC on Wednesday. Forecast soundings show enough drying to erode the lingering low clouds and/or fog early Wednesday, with daytime heat into the mid 50s (per statistical guidance) likely to result in a cu field, mainly east. Weak but moist southerly flow should redevelop late Wednesday in response to weak height falls and an intense upper jet associated with the aforementioned cold front and result stratus Wednesday night. Lows 39-44. The cold front, progged to be just west of the Yadkin early Thursday morning, will will cross the area during the first half of the day, with strong cold advection behind it Thursday evening and overnight. The front itself is not expected to produce much precip, if any, though the GFS cranks out some light qpf, owing likely to a period of strong low-level FGEN and sufficiently deep moisture across the northern half of the area. The current slight chance POP will be maintained. Highs in the upper 40s to mid 50s. Strong cold advection Thursday night should result in gusts to 15- 20kt and wind chills in the upper teens, as lows drop into the mid to upper 20s. Arctic high pressure will then build in over the weekend, with forecast thicknesses progged to approach 1270m Sat/Sun morning. Lows should have little problem hitting the upper teens and lower 20s. The high then quickly moves offshore and the synoptic front return north with the next chance of rain early next week. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... As of 330 PM Monday... Initially VFR conditions through this evening will yield to progressively lowering ceilings tonight, into IFR-MVFR range late tonight-early Tue, as lift and moisture increase downstream of a complex low pressure system approaching from the SW. Patchy light rain will also begin to fall from the VFR ceilings this evening, then increase in coverage and intensity through early Tue. A few rumbles of (elevated) thunder, whose cloud bases would be rooted around 5000 ft owing to a cold and stable low level air mass, will be possible roughly between 14-18Z Tue, as lapse rates aloft briefly steepen with the passage of a mid-upper level trough. The passage of the trough axis will also cause widespread rain to end, and clearing to commence, from SW to NE throughout the afternoon and early evening hours. The clearing, in conjunction with wet soil, will result in the development of patchy fog Tue night. Outlook: Chance of MVFR ceilings ahead of an arctic cold front Wed night-Thu, and blustery NW winds behind the front late Thu-Thu night. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MWS LONG TERM...SMITH AVIATION...MWS

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