Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201821 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 221 PM EDT SAT AUG 20 2016 .SYNOPSIS... An upper level trough and attendant cold front will approach the region from the west tonight, then progress east across the Mid- Atlantic and Carolinas Sunday into Sunday night. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Saturday... Generally flat flow continues across the Southeast US, though some ridging is noted across the TN valley and more northwesterly mid/upper level flow at KGSO this morning. At the surface, a remnant trough, modulated by outflow last evening, appears to have settled across the Sandhills and southern coastal plain, though radar imagery from last night suggests an outflow boundary may arch back across the central and northern Piedmont. northerly 850mb flow is advecting some drier air across the northern half of the CWA and the higher, near 2 inch PWs are confined to the south and east where RAP/HRRR soundings indicate MLCAPE of around 1500 j/kg will develop this afternoon. There aren`t any really obvious disturbances aloft in water vapor, so coverage may not be as great as yesterday, but the best coverage should be from Albemarle toward Fayetteville based the morning analysis and CAM guidance. A ribbon of 25kt mid- ]level flow should still support at least an isolated strong storm or two, and those storms a little further north toward HWY 64 may have a little better DCAPE environment to work with. Overall changes to the forecast grids are minimal, with highs still expected to reach the upper 80s and lower 90s as morning stratus over the coastal plain burns off. Lows in the lower 70s tonight as mostly diurnally driven convection dies off by midnight. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 345 AM Saturday... Flow aloft will further strengthen Sun/Sun night as the aforementioned upper low progresses ENE into southern Canada and additional shortwave energy digging southeast through the central MS river valley amplifies an upper level trough over the OH valley and Great Lakes, and an attendant surface cold front approaches from the NW Sunday afternoon, progressing through central NC sunday evening/ night. Expect the best overall potential for convection this weekend to occur late Sunday afternoon through Sunday evening as the surface cold front /low-level trough/ progresses into the region in vicinity of peak heating in the presence of above normal moisture, marginal to moderate destabilization, and small amplitude waves embedded within relatively speedy westerly flow aloft. Deep moisture /cloud-cover/ and weak mid-level lapse rates may temper instability such that more favorable deep layer shear attendant stronger flow aloft may not be fully realized/capitalized upon by updrafts at this latitude. Weak DCAPE suggests weak cold pools, though ~20 kt westerly flow in the lower-levels may support upscale growth /downdraft consolidation/ and eastward propagation, perhaps evolving into a multicells line along/east of hwy 1 with an isolated potential for damaging winds via precip loading and downward momentum transport. Regardless, expect the best potential for convection in the late afternoon and evening, ending from west-east Sunday evening/night as the surface front low-level trough progress east toward the Carolina coast. Expect highs in the upper 80s to lower 90s and lows Sunday night driven by cold advection, ranging from the lower/mid 60s far NW to lower 70s far SE. -Vincent && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 245 AM Saturday... Surface high pressure will build into the area behind the cold front early next week, resulting in much lower afternoon humidity values and temps near to below normal along with dry weather. The surface high will slowly shift off the Mid-Atlantic coast mid to late week, allowing for moisture and temps to slowly increase. However, dry weather is generally expected to continue through the end of the workweek. High temps are expected to be in the 80s early to mid week, before increasing into the upper 80s to lower 90s by late week. Low temps will follow a similar trend, with lows generally in the 60s throughout the week though (with possibly a few 50s in the usual rural cool spots early to midweek). && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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As of 210 PM Saturday... VFR conditions this afternoon, with brief periods of sub-VFR possible within showers and storms that are developing in an axis of low-level convergence that extends from KFAY northwest toward KGSO/KINT and KTDF. Most of the convection should diminish by 06z and yield predominately VFR conditions through the overnight period as a light southwest wind develops. Some areas of IFR ceilings are possible late, though the best chance should be east of KRWI. On Sunday, a cold front will approach from the west and cross the area between 21z and 03z Monday, with scattered (south) to numerous (north) showers and storms. Looking ahead: Showers and storms will be moving through the area Sunday evening and east of the area Sunday night, followed by VFR conditions through at least midweek.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH/VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...BSD AVIATION...SMITH

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