Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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513 FXUS62 KRAH 170531 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1230 AM EST Sun Dec 17 2017 .SYNOPSIS... High pressure will settle east across the southeastern US through the weekend. A series of upper level disturbances will move through the region through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 942 PM Saturday... Only a few thin cirrus were racing NE across NC this evening as ridging remains firmly in place. Based on satellite and the latest observational data it will be around daybreak before the mid level moisture is able to reach our SW Piedmont. The bulk of the night is expected to be mostly clear and cold. Temperatures at mid-evening were showing the typical wide range due to calm conditions. Readings around 900 PM ranged from the upper 20s to upper 30s. Expect lows solidly in the 20s in rural areas, ranging to near 30 in urban centers. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 355 PM Saturday... The open wave now lifting across the Big Bend area will get strongly- sheared/crushed in confluent and zonal flow, across the OH Valley and middle Atlantic states Sun and early Sun night, then offshore. Associated weak height falls aloft, on the order of 10-20 meters at 500 mb, for example, will glance cntl NC in the several hours centered around 00Z Mon. Preceding mid-high level moisture that will have begun to stream into at least w-cntl NC late tonight will thicken and lower throughout the day. Ceilings will consequently continue to lower, to between 5 and 10 thousand ft after 18Z Sun, with associated widespread virga owing to strong omega and saturation in a mid-level mixed phase layer. Some of this precipitation aloft may reach the ground in the form of patchy light rain or sprinkles by late Sun afternoon and Sun evening, particularly across the nrn and nwrn Piedmont, where the aforementioned height falls aloft, and lift and saturation, are expected to be maximized. Skies may partially clear Sun night, though the approach of a maritime warm front from the Deep South may result in the redevelopment of clouds over srn NC late, though this time lower level ones in a several thousand ft layer centered around 5-6 thousand, with an associated slight chance of warm rain process light rain there, as a strengthening and increasingly moist wswly llj jet isentropically-ascends the retreating sfc frontal zone. The periods of cloudiness will likely affect both high and low temperatures, most notably over the wrn and nrn piedmont during the day, and over the srn Piedmont and Sandhills overnight. Highs 49 to 58 from nnw to sse; and lows from the upr 30s north to lwr-middle 40 south. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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As of 330 PM Saturday... There has been a lot of north-south variation from model run to run in the position of the warm frontal zone over the past couple of days, but it looks like the moisture conveyor associated with a warm frontal zone will remain pinned south of the area during the early extended period. Low amplitude ridging and low level westerly flow will maintain our mild airmass with highs in the low and mid 60s both Monday and Tuesday. Min temperatures will be milder as well, with morning lows mostly low to mid 40s. PoPs both days will be in the slight chance range and limited to the southern tier counties. Ejection and subsequent eastward acceleration of a cutoff low over the 4 corners region will lift the frontal zone northward Tuesday night, with increased changes for showers Wednesday through Wednesday night as the dampening remnants of the wave move across the area. PoPs will still be focused across the southern tier, ranging from ~30% north to 50% south. Increased cloudiness and shower coverage will suppress highs on Wednesday to the mid and upper 50s, while modestly cooler air will settle briefly down the Atlantic coast in resulting northeast flow as the low moves offshore Thursday to produce highs mostly in the lower 50s. Re-amplification of the subtropical ridge will result in a quick return to southwest flow with moisture on the rebound along with temperatures as we head into Friday and Saturday. Highs both days should reach 55 to 60, and the chance of showers will be increasing in the west Friday night, with chance PoPs across the area on Saturday.
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&& .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 1230 AM Sunday... Mid-level moisture plume associated with the de-amplifying southern stream shortwave that will track on the western and northern periphery of the mid/upper level ridge in place across the SE US will result in ceilings gradually lowering to the 4-5kft thousand foot range late this afternoon and evening. There could be fairly widespread virga that may reach the ground in the form of patchy light rain or sprinkles between 18Z Sun through 03Z Mon. It`s possible that ceilings could briefly lower to MVFR at KFAY between 06 to 12z. Outlook: Drier air will build into the area on Monday and Tuesday. There will then be a high chance of rain and sub-VFR conditions, heaviest and lowest at FAY, late Tue night through Wed night, with the passage of a low pressure system across the sern U.S.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...np NEAR TERM...Badgett/MWS SHORT TERM...MWS LONG TERM...MLM AVIATION...CBL/MWS

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