Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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777 FXUS62 KRAH 231451 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1050 AM EDT Mon Apr 23 2018 .SYNOPSIS... Strong high pressure will remain nearly stationary or slowly drift off the New England coast through tonight. Low pressure approach from the Tennessee Valley today and tonight, then track slowly east over SC on Tuesday, then NE across eastern NC late Tuesday and Tuesday night. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1050 AM Monday... Little adjustment required to the near term forecast. 12Z upper air analysis depicts a stout se flow in the lowest 10k ft of the atmosphere. This flow expected to strengthen later today into tonight as the pressure gradient tightens between a sfc low immediately to our west-southwest to a strong high offshore of New England. Sustained sfc winds 15-20 mph probable with gusts around 30 mph common. This fetch off of the southern Atlantic will pull abundant moisture into the region. This available moisture in conjunction with lift provided by an approaching s/w and central NC in the favored left exit region of a 80-90kts crossing the Deep South will result in bands of moderate to locally heavy rainfall across the region this afternoon, through tonight. Rainfall amounts on the order of one-two inches look reachable. The rain encroaching upon central NC from the southwest will cause temperatures to hold steady this afternoon roughly south and west of Raleigh, while temperatures should continue through mid afternoon for locations north and east of Raleigh. Temperatures will change little this evening into the overnight, ranging from the low-mid 50s NW to the upper 50s SE.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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As of 350 AM Monday... An elongated srn stream mid-upr low over the mid-South this morning is forecast to wobble to near Nashville, TN by 12Z Tue and to swrn VA by 12Z Wed. Preceding the upr low, the right entrance region of a strengthening sly to ssely, 80-100 kt upr level jet will stream across e-cntl NC and sern VA through 18Z Tue. Associated divergence aloft, atop a strong low level WAA/isentropic upglide regime courtesy of a 40-45 kt low lvl jet, will support ongoing widespread rain and embedded elevated convection (showers), early Tue. This regime will lift newd into and offshore VA through early afternoon, followed by a mid level dry slot that will nose across the Carolinas Tue afternoon and evening. At the surface, the models indicate a triple point low over nern GA/wrn SC at 12Z Tue will track newd into the srn NC Piedmont/wrn Sandhills by 00Z Wed, then track nnewd roughly along US Highway 1 Tue night. A preceding warm front will arc enewd across srn and sern NC early Tue, with the trailing cold front extending swd along the srn SC and GA coast. The cold front is forecast to progress ewd more quickly than the warm front retreats nwd, with an associated increasingly narrow wedge of warm sector characterized by low-mid 60s surface dewpoints and mainly weak sfc-based instability, which is forecast to pivot newd across nern SC and ern and e-cntl NC Tue afternoon, beneath the aforementioned mid lvl dry slot. Low lvl and deep layer flow will have weakened considerably and veered in the wake of the early day WAA/isentropically-driven rain, though lingering effective SRH on the order of 100-150 m2/s2 immediately preceding the surface wave may support episodic low level rotation in showers/storms late Tue aft-evening. However, a lack of more appreciable instability and shear suggests any severe weather threat over cntl NC should be limited. Showers will linger Tue night, particularly over the Piedmont, as the mid-upr low and associated cold pool aloft pivot overhead. Temperatures Tue are expected to range from low-mid 60s in a lingering damming regime over the NW Piedmont (nw of the track of the surface low), to low-mid 70s across the Sandhills and srn-cntl Coastal Plain, with lows in the 50s.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 400 AM Monday... An energetic, unsettled pattern will persist through most of the medium range, though uncertainty regarding amplitude and phasing of associated shortwave troughs migrating through the energetic flow lend low forecast confidence for prospects for rainfall in cntl NC. A trough now over the PAC NW will have amplified into the cntl Plains by 12Z Wed, and into the TN Valley/srn Appalachians by 00Z Fri, before then deamplifying across the Carolinas/srn middle Atlantic states through early Fri. A full latitude trough will follow quickly on the heels of the lead trough and pivot ewd across the Appalachians and NC Fri night-Sat. Following NW flow downstream of progressive ridging aloft will overspread the srn middle Atlantic region for end of weekend and early next week. This pattern will favor variably to mostly cloudy conditions and above climo chances of rain by late Thu-Fri, followed by lingering slight chances Fri night-Sat given the aforementioned uncertainty regarding shortwave details, and dry conditions as the NW flow takes hold by Sun.High temperatures will be seasonable/slightly below average - mostly in the lwr-mid 70s, with near to slightly above average low temperatures, in the upr 40s to lwr-mid 50s. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 659 AM Monday... MVFR to VFR CIGS will lower to IFR TO LIFR CIGS and IFR VSBYS with rain and fog later today and tonight. Winds will increase from the east at 15-20kt with gusts to 30kt this afternoon and tonight. Looking beyond 12z Tue: Poor aviation conditions will dominate all sites through Tuesday. Mostly IFR CIGS and IFR to MVFR VSBYS with areas of rain and showers are likely on Tuesday, before tapering off Tuesday night. Sub-VFR stratus/fog may linger into Wed morning. VFR conditions should return Wed, although a few showers are possible Wed afternoon, and again Thu into Fri, as a series of upper level troughs cross the region, bringing unsettled weather and perhaps brief periods of sub-VFR conditions. && .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...Badgett/Hartfield NEAR TERM...WSS SHORT TERM...MWS LONG TERM...MWS AVIATION...Badgett

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