Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 131955 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 255 PM EST Wed Dec 13 2017 .SYNOPSIS... A fast moving upper level disturbance will move just north of the region tonight, and will be followed by a weak surface cold front that is expected to pass across central North Carolina Thursday morning. High pressure will then build into the area by late Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 248 PM Wednesday... Latest water vapor shows the next short wave trough crossing the Midwest and western Great Lakes regions. This wave will continue tracking to the SE then E, passing by to the north of our area later this evening and overnight. The attendant sfc cold front will lag a bit behind...not expected to cross central NC (uneventfully) until just after sunrise Thursday morning. Other than a brief increase in mid and high clouds on the southern tail end of the system, and perhaps a bit of a light breeze (rather than the typical calm or light winds that we usually see overnight)...we`re not expecting any notable weather or impacts from this system. In terms of temps...look for a subtle warming trend ahead of the cold front, thus lows tonight will likely be several degrees warmer than last night, but still falling below freezing across most if not all of our zones. Lows in the upper 20s. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 248 PM Wednesday... Fair weather is in store for Thursday in the wake of tonight`s departing short wave trough and the sfc cold front continuing to push south of our area. With the upper flow becoming westerly, look for the high clouds currently located over the central Plains to gradually move eastward and across our area. Otherwise, with low level thicknesses remaining close to their pre-frontal values (some 30-40m higher than today), we should see highs at least 8-10 degrees warmer than today. Overall, Thursday will be partly cloudy with highs in the lower 50s. Thursday evening the low level wind field will shift to the N/NE as high pressure over the Ohio Valley moves east. Although low level thicknesses may drop a few meters on this N/NE flow...increasing high clouds from the southwest should offset the cooler airmass. Lows in the upper 20s to around 30 under partly cloudy skies. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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As of 255 PM Wednesday... A strong upper short wave moving across the Ohio Valley will nudge a reinforcing surge of cold air into the area. Surface high pressure will then build across the area, resulting in plenty of sun, but suppressing high temperatures to the 40s Friday and Saturday. Morning lows Saturday will be mostly upper 20s, with some areas across the south only falling to near freezing. Short wave ridging will be amplifying north into the Eastern Conus by Saturday night, with increasing heights and initiation of warm air advection in return flow as the surface high moves offshore. Cloudiness will be on the increase by later Sunday with highs reaching mostly low and mid 50s after a morning low near freezing. By Monday, a low pressure area will be lifing northeast out of the Gulf of Mexico. There is a good deal of uncertainty as to how the details will play out, with model timing issues as the ECMWF has a strong fast moving short wave race across the Ohio Valley to kick the system offshore quickly, resulting in precip pretty much limited to the southeast, while the GFS`s slower short wave allows for a couple of waves to ride up the upper ridge into the area to produce more widespread precip and prolonging the duration of precip chances into Tuesday. Will maintain our ongoing forecast of chance PoPs from Sunday night through Tuesday and allow details to emerge from later model consensus. That said, precipitation type will be no problem with southern stream flow into the area allowing highs Monday and Tuesday to reach the 50s after morning lows in the low to mid 40s. Wednesday looks to be a dry and a bit cooler, but still near seasonable in the 50 to 55 range.
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&& .AVIATION /12Z WEDNESDAY THROUGH MONDAY/... As of 1232 PM Wednesday... Through 14/18z: Mainly clear skies will persist through the rest of the afternoon, then mid and high clouds will briefly cross north- central NC between 14/00z-14/07z, associated with the the next short wave passing by to our north. HRRR forecast soundings hint that a brief period of LLWS is possible during those evening and early overnight hours, thus have included it at all TAF sites. Otherwise, VFR conditions through the TAF period. After 14/18Z: VFR conditions expected through the rest of the week. A southern stream system may bring increased moisture and risk for reduced flight conditions early next week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...np NEAR TERM...np SHORT TERM...np LONG TERM...mlm AVIATION...np

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