Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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731 FXUS62 KRAH 231724 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 125 PM EDT Wed May 23 2018 .SYNOPSIS... A cold front will approach from the northwest this afternoon, and then push southeast through central North Carolina tonight. This front will settle across South Carolina Thursday through Friday, as high pressure builds in from the northeast. && .NEAR TERM /THROUGH TONIGHT/... As of 1050 AM Wednesday... Little change required to the near term forecast. Still appears that a few strong/locally severe t-storms probable later this afternoon through early evening, primarily northeast and east of Raleigh. 12Z upper air analysis depict a weak low-mid trough bisecting the region with a slightly stronger mid level trough exiting the central Appalachians. The east-southeastward progression of this secondary trough will aid to propel a sfc cold front close to the NC/VA border by late afternoon. Heating of the moist atmosphere will yield a moderately unstable air mass with surface based CAPE values projected to be in excess of 3500 J/kg over the northern/central Coastal Plain, and MLCAPE around 2000 J/kg. Shear values not too shabby with effective bulk shear around 30 kts, supportive of organized convection. Thus, bulk of the strong/severe parameters are still pointing toward the northeast Piedmont into the Coastal Plain from mid afternoon through early evening. Character of the storms still favors multi-cellular though a few parameters hint of potential for isolated super cells, mainly over the Coastal Plain east of I-95. Main severe weather hazards will be strong/locally damaging wind gusts, and marginally large hail. Wly steering flow of around 20kts suggest that there should be enough movement to the storms to lessen the threat for flash flooding. Timing wise, appears best parameters for scattered-numerous convection occur between 3 PM and 9 PM. Partly-mostly sunny skies through early afternoon will boost temperatures solidly into the mid 80s with a few upper 80s possible across the eastern Piedmont, Sandhills, and Coastal Plain. Tonight, as the sfc front sags southward, the focus for scattered convection will also shift southward, with most of the scattered convection after 9 PM occurring south of highway 64. Farther into the night, convection will gradually dwindle down to isolated across the southern tier overnight. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 305 AM Wednesday... All but the southern third of the forecast area is expected to be mostly dry. The broad mid level trough will continue to push ESE and offshore Thu morning, while the surface cold front will have settled just to our south, as high pressure builds in from the N. Models depict a lingering moisture axis near the front spanning southern NC through Thu/Thu night, with warmer temps and higher dewpoints here supporting scattered showers and perhaps a few storms. Will retain low chance pops and mostly cloudy skies across the S Thu, with no pops and fair skies over the N. Highs from the lower 80s N to mid 80s S. As the low level anticyclone center moves over and off New England, the degree and depth of low level upslope-directed flow should allow low pops to drift into the SW CWA, and will hold only 15-25% rain chances across the SW sections Thu night. Fair skies elsewhere. Lows from the upper 50s NE to the mid 60s S. -GIH && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 315 AM Wednesday... An elongated east/west oriented surface high just to our north will try to keep central NC dry on Friday but a moisture ridden airmass lingering to the south will try to bring precipitation into our southern and western counties, with the emphasis still on diurnal convection. Chances for precipitation will increase later in the day as the surface high pulls out to sea and the return flow around the Bermuda high takes back over. Highs in the low to mid 80s with dewpoints in the low to middle 60s will feel drier, but again this could be short lived as more moist air returns for the evening hours. All eyes will be to the south for the holiday weekend as a low pressure system with tropical characteristics will develop over the Gulf of Mexico and move northward. Run to run consistency in the ECMWF solution makes it the more favorable solution at this point, which takes the system to the northwest and over Louisiana by Sunday. This system will bring moisture transport northward into the Carolinas but that doesn`t yet mean that the weekend will be a total washout. At this point the best chance for convection on Saturday will be in the western Piedmont with the same type of hit and miss showers possible anywhere across the CWA. Highs in the mid to upper 80s. By Sunday, the moisture begins to be focused more towards the low, which will actually work to force it westward and away from NC. This could lead to a relatively dry Sunday but with increased cloud cover. This will drop temps back into the low 80s for daytime highs. By Memorial Day, moisture reinforcements will arrive and this looks to be the day with the most convective coverage, particularly during the afternoon hours. Highs in the low 80s once again. More of the same for Tuesday despite the fact that models handle the tropical low much differently at this point with the ECMWF solution still spinning over Louisiana and the GFS a mere remnant of its former self. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 125 PM Wednesday... While VFR parameters will persist across central NC through Thursday evening, there will be brief periods of MVFR/IFR ceilings. Scattered convection this afternoon through early evening will produce instance of sub VFR ceilings/visibilities. The threat for convection appears highest in proximity of KRWI and KFAY, mainly between 20Z through 24Z. In vicinity of the stronger convection, wind gusts 30-35kts may occur along with small hail. After 06Z, areas of low stratus will develop in the NE low level flow behind the departing sfc cold front. The threat for these low ceilings appears greatest over all the region except the Triad region, mainly between 09Z-14Z Thursday. A stable air mass will overspread the majority of the central NC Thursday and Thursday night, maintaining the VFR conditions. The only threat for isolated-scattered convection should be across the southern Piedmont, well south of the Triad, and west of KFAY. The atmosphere is projected to become increasingly moist and unstable from Friday and beyond, especially during the later half of the holiday weekend. This should lead to extended periods of sub VFR conditions, primarily related to ceilings.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...WSS SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...WSS

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