Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180546 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 146 AM EDT Fri May 18 2018 .SYNOPSIS...
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An area of low pressure will drift slowly northward across the Southeast U.S. through today, bringing an increased threat for showers and few thunderstorms to central NC.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 945 PM Thursday... Deep cyclonic southerly flow continues to draw moist air into NC, with PW holding at 150-200% of normal in the area and upstream. 00z upper air analyses depict the mid level low over MO, with the lower level circulation center further SE between Tupelo MS and Muscle Shoals AL. A subtle/weak southerly upper jetlet over N FL across GA will translate northward into the S Appalachians tonight, boosting weak upper divergence the region, while in the low levels, the 925 moisture transport maximum will surge into central and eastern NC. The greatest shower and isolated storm coverage in the last several hours has been between the Highway 1 and I-95 corridors, at the nose of the northwest-pushing 925 mb jet, and as this continues to translate to the NW, as the HRRR has indicated, the band of showers should continue a NW translation through the CWA, reaching the NW Piedmont late tonight. Otherwise, while moisture remains plentiful, there is little dynamic support for strong ascent, so any other showers should be scattered and disorganized, with a diminishing storm threat given weak to absent deep layer shear, dwindling CAPE with nightfall, and poor mid level lapse rates. Will keep a band of likely to categorical pops tracking to the NW overnight, while maintaining at least chance pops elsewhere, with isolated storms for another few hours. Another sticky night, with lows in the upper 60s to lower 70s. -GIH Earlier discussion from 315 PM: Afternoon convection is a little less than earlier anticipated, and this may be attributed to one or two factors: 1.) Minor perturbation aloft lifting north-northeast from central SC into central NC. The best lift associated with this feature occurring to its east and north, or essentially along and east of highway 1; 2.) cluster of showers and storms over north central SC disrupting the 850mb moisture transport into central NC, cutting off the better inflow into the Piedmont. As the upper level feature lifts farther east-ne, 850mb moisture transport should become re-established this evening, leading to a likely uptick in convective coverage this evening. With loss of heating, should see a downward trend late this evening into the overnight. That being said, the abundantly moist air mass and the relatively close proximity of the upper level low over the Mid- South, a threat for scattered showers will persist through the night. The showers and storms will be efficient rain producers thanks to the available moisture, and with the deep sly flow, the convection will train repeatedly over the same location. This may lead to minor flooding of streets and low lying areas. Overnight temperatures in the upper 60s-lower 70s. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 315 PM Thursday... The weather pattern changes little Friday and Friday night as the mid-upper level low traverses slowly east, and maintains a deep sly flow over central NC. Perturbations in this flow should trigger numerous showers and storms, especially during the heat of the afternoon into the evening hours. Coverage Friday afternoon-evening may be enhanced by a decent perturbation or s/w depicted by the majority of the models, lifting newd from SC. If this materializes, a steady band of convection may result, increasing the threat for locally excessive rainfall. Based on expected sfc pattern, the Piedmont counties may be more under the gun through Friday afternoon, with the heavy rain threat shifting east into the Coastal Plain Friday night. Will hold off on the issuance of a Flash Flood Watch at this time, and see where the heavy rain occurs tonight, and see if models begin to indicate a stronger signal (such as stronger low level convergence) for Friday-Friday afternoon. Extensive cloudiness and scattered/numerous convection will hold temperatures mainly in the 70s to around 80 Friday afternoon. Overnight temperatures Friday night in the 65-70 degree range. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 255 PM Thursday... The long term period will feature a gradual easing of the ongoing wet pattern into more scattered rain chances as we head into the middle of next week. The start of the long term period will feature an amplified pattern with the sub-tropical ridge off the southeast coast and a shearing trough across the OH and TN Valleys. A deep southerly flow will drive an axis of convection across central and eastern NC on Saturday that will shift east on Sunday. Fairly widespread showers and thunderstorms are expected on Saturday with a bit less coverage and a greater focus to the east on Sunday. While the trough departs early next week, a weakness aloft persists on Monday and Tuesday that will support more scattered, mainly afternoon and evening showers and storms. The approach of a backdoor cold front late Tuesday into Wednesday will support scattered storms with a drier air mass reducing storm coverage on Thursday. With very little air mass change, a good deal of cloudiness and at least scattered convection, highs will consistently range in the lower to mid 80s with low mainly in the mid to upper 60s. -Blaes && .AVIATION /06Z FRIDAY THROUGH WEDNESDAY/...
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As of 145 AM Friday... 24-Hour TAF Period: Scattered showers and isolated thunderstorms continue across Central NC. Most of the heavier showers and storms look to miss the main terminals, though KINT and KGSO could still see some heavy rain over the next couple hours. Ceilings will predominantly be around 1500 ft for the remainder of the overnight, with some sites dropping to around 600 ft before sunrise today. Expect any LIFR/IFR cigs to lift back into the MVFR/VFR range this morning. Some sub-vfr visbys will also be possible for brief periods tonight, mainly accompanied by heavier showers, but the cigs will be the lower category parameter. Expect more by the way of showers and thunderstorms today, resulting in periods of very heavy rain and accompanied by low visbys and gusty winds at the affected terminals. Looking ahead: The pattern of daytime showers and thunderstorms resulting in heavy rain and reduced visbys, with a relative lull in precipitation accompanied by sub-vfr cigs and visbys overnight, will continue into early next week.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...Hartfield/WSS SHORT TERM...WSS LONG TERM...BLAES AVIATION...KC

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