Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281336 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 936 AM EDT Sun May 28 2017 .SYNOPSIS... A series of upper level disturbances will track east across the Carolinas this afternoon through Monday evening. && .NEAR TERM /THROUGH TONIGHT/... As of 930 AM EDT Sunday... Shower activity in southern VA this morning appears to be associated with an MCV (emanating from an MCS that decayed over central NC earlier this morning) along with H85 warm advection atop a surface front stalled in vicinity of the NC/VA border. Differential heating assoc/w overcast skies and precipitation in southern/central VA will enhance the gradient in vicinity of the NC/VA border by late morning/early afternoon. The EML in place over the Carolinas the past few days has been modified and suppressed southward by numerous rounds of convection over the past 24 hours, with H7-H5 lapse rates ranging from ~5.5c/km near the VA border to ~7C/km near the SC border. Diurnal destabilization this afternoon is expected to range from marginal (~500 J/kg MLCAPE) near the VA border to moderate (1500-2000 J/kg MLCAPE) near the SC border where the strongest insolation and richest low-level moisture will be juxtaposed with mid-level lapse rates on the order of 6.5-7c/km. With numerous MCVs upstream of the Carolinas this morning, significant uncertainty is present with regard to the timing/ coverage of convection this aft/eve. Convection allowing models such as the 06Z HRRR and NAM NEST suggest scattered convection will develop over western NC around ~21Z and propagate east across central NC through 00-03Z this evening, presumably in association with one of several MCVs expected to track across portions of the Carolinas. Moderate destabilization, effective shear on the order of 40-50 knots, straight hodographs, and relatively steep mid-level lapse rates across the SW Piedmont/Sandhills suggest the primary mode of convection (should it develop) will be splitting supercells with an attendant threat for large hail (1.50-2.00") and damaging winds. Diurnal destabilization will be weaker north of Hwy 64, particularly in the NE Coastal Plain where weak mid-level lapse rates will be juxtaposed with a cooler airmass in vicinity of the stalled front near the VA border. Relatively steep (6.0-6.5 c/km) mid-level lapse rates expected to advect into portions of the W/NW Piedmont this afternoon will enhance diurnal destabilization (compared to the NE Coastal Plain) amidst 35-45 knots of effective shear. As a result, a conditional potential for splitting supercells capable of producing large hail (albeit smaller than near the SC border) and damaging winds will exist in the W/NW Piedmont, as well. Expect highs this afternoon to range from the lower 90s near the SC border to the lower/mid 80s north, coolest near the VA border in the Northern Piedmont and NE Coastal Plain. Lows tonight should range from the mid/upper 60s near the VA border to lower 70s near the SC border. -Vincent && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 230 AM EDT Sunday... Monday and Monday night: A marginal to slight risk of severe storms expected again Monday afternoon and evening, mainly in the eastern counties. A cold front is forecast to push into the region Monday and Monday evening. Timing of the front is in question, but the slower models may be best. However, any convective outflows may be the main thing to watch for additional strong to locally severe storms Monday afternoon and evening. Both the GFS and EC are in reasonable agreement with the placement of the forecast highest instability and suggest that MLCAPE values could again reach the 1500 to 2000 J/kg range, mainly over the Coastal Plain, where heating may be best. Highs should reach the mid to upper 80s with dew points in the upper 60s. This area should also be in the region of strongest shear with 35-40kt of WSW flow expected (0-6 km). The main threats should be large hail and damaging wind gusts. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 345 AM EDT Sunday... A deep mid/upper level trough is expected across the eastern half of the country next week, with the associated deep mid/upper low expected to slowly wobble eastward across SE Canada/NE U.S. An associated weak cold front will stall/dissipate across eastern portions of the area on Tuesday, with another weak cold front settling south and eastward across the area on Wednesday. This should result in a continued threat of showers and storms across mainly south and eastern portions of the area on Tuesday and areawide Wednesday. However, will keep pops in the low chance/slight chance categories, given differences in model guidance timing of hard to track low amplitude disturbance this far out in the forecast. High temps will generally be in the 80s during this time frame, with lows in the 60s. Surface high pressure will move across the area on Thursday, resulting in generally a dry day, as mid level flow becomes westerly. Mainly diurnal chances of showers and storms are expected on Friday and Saturday as surface high pressure shifts offshore. High temps late week into the weekend are generally expected to be in the 80s and lows in the 60s, near seasonal norms. && .AVIATION /12Z SUNDAY THROUGH WEDNESDAY/... As of 650 AM EDT Sunday... Generally VFR conditions expected today until the chance of storms develops this afternoon. Any TAF site having a 50/50 chance of a period of storms, mostly likely less than an hour at any site. All told, outside of convection, VFR conditions are expected through the 24 hour TAF period, although there could be patches of MVFR fog in the predawn at locations which do receive rain. Outlook: There be a chance of mainly late day storms Monday through Wednesday as a cold front slowly approaches from the west and potentially stalls over the area. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Badgett LONG TERM...BSD AVIATION...Badgett

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