Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 141746 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 146 PM EDT Mon Aug 14 2017 .SYNOPSIS... A front stalled across portions of central North Carolina will gradually wash out and dissipate by mid-week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 145 PM Monday... Challenging forecast. Central NC remains situated at the southern periphery of the westerlies in SW flow aloft. Upper level forcing will be limited to small amplitude waves progressing across the far N/NW Piedmont. The cold front that progressed southward into central NC yesterday remains stalled over the region. At 17Z, the boundary was located over portions of the Sandhills and Coastal Plain, extending (roughly) SW-NE from Wadesboro to Rocky Mount. The boundary should remain nearly stationary through tonight, though some meandering is likely in assoc/w differential heating and convective outflow this afternoon. Regardless, forcing assoc/w this feature will be very weak in nature and confined to shallow convergence. Diurnal destabilization is expected to yield marginal MLCAPE (250-500 J/kg) in the north (weakest along/north of I-85) to moderate MLCAPE (1000-1500 J/kg) in the south (strongest near the NC/SC border) this afternoon. With the above in mind, expect the best potential for convection in the N/NW Piedmont where episodic DPVA will augment forcing and offset weaker instability. Further S/SE, instability will be greater, however, coverage is likely to be isolated in nature due to weak forcing. The latest guidance suggests small amplitude waves are most likely to traverse the region this evening/overnight, and convective coverage may be greatest after sunset. Expect highs ranging from the upper 70s to lower 80s near the VA border to upper 80s /90F/ near the SC border. Lows tonight in the lower/mid 70s, warmest S/SE. -Vincent
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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As of 145 PM Monday... With little change in the synoptic pattern, expect conditions similar to today, though a fair amount of uncertainty persists w/regard to the spatial/temporal extent of cloud cover, convection, and high temperatures. Like today, convective coverage/timing may largely be dictated by small amplitude waves in WSW/SW flow aloft. With the above in mind, will indicate a 50% chance of showers/storms across the area, primarily during the aft/eve hours, with highs in the mid 80s (N) to ~90F (S) and lows in the lower/mid 70s. -Vincent
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&& .LONG TERM /WEDNESDAY THROUGH TUESDAY/... As of 240 AM Monday... There is still quite a bit of uncertainty with respect to where and when the best chances for convection will be during this part of the forecast, resulting in below average confidence. Wednesday through Thursday Night: Expect the climatological diurnal convection through the period (higher chances during the aft/eve, general lull overnight into the early morning hours. Medium range models also suggest the highest chances will be along the sea breeze and in the lee of the Appalachians. The upper level pattern will be characterized by high pressure over the deep south and weak cyclonic flow over and north of Central NC. The surface pattern will consist of a weak low/trough over the eastern half of the region with weak high pressure ridging into the northwest. Temperatures will be on the increase, with highs increasing from the mid 80s North to near 90 degrees South on Wednesday to upper 80s to low 90s on Thursday. Lows generally in the 69-75 degree range, highest southeast. Saturday through Monday: A cold front is expected to approach the Carolinas on Friday and impinge on Central NC Friday night into Saturday. It is unclear at this time if, and how far, the front will progress into the area since the medium-range models really diverge at that point. Meanwhile aloft, an upper level shortwave disturbance will swing through the Great Lakes and Ohio Valley. As stated above, details regarding timing, coverage and location of the convection during this part of the forecast are highly uncertain. As for Temperatures, highs will top out in the low to mid 90s on Friday, gradually decreasing thereafter. Lows will generally range from upper 60s to mid 70s through the rest of the extended period. Although it is at the tail end of the extended period, the partial solar eclipse expected over the region on Monday will result in a period of lower temperatures Monday afternoon. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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As of 145 PM Monday... 24-hr TAF Period: As of 17Z, LIFR ceilings persisted at the INT/GSO terminals, though RDU/RWI have improved to MVFR and FAY to VFR. Expect further improvement mid/late afternoon, with VFR conditions possible at RDU/RWI/FAY terminals (esp FAY). LIFR conditions at the INT/GSO terminals should improve to IFR and possibly MVFR mid/late afternoon, though confidence is lower. Convection could potentially affect any terminal this aft/eve, though the relative best chance should be at the INT/GSO terminals. With little change in pattern/ airmass, IFR/LIFR ceilings are expected to re-develop at all terminals late this evening/tonight. Winds will be light/variable throughout the TAF period. Looking Ahead: With relatively little change in the synoptic pattern, adverse conditions associated with diurnal convection (primarily 18-03Z) and early morning stratus (primarily 06-15Z) are likely to persist through mid-late week. -Vincent
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...KC AVIATION...Vincent

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