Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 141503 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1103 AM EDT Mon Aug 14 2017 .SYNOPSIS...
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A front stalled across portions of central North Carolina will gradually wash out and dissipate by mid-week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 1100 AM Monday... Challenging forecast. The cold front that progressed S/SW into central NC yesterday has since stalled over the region. At 14Z, the stalled frontal zone was located over portions of the Sandhills and Coastal Plain, extending SW-NE from Rockingham to Lillington to Rocky Mount. The boundary is expected to remain nearly stationary through tonight, though some meandering is likely in assoc/w differential heating and convection/outflow this afternoon. Regardless, forcing with this feature will be confined to very weak/shallow convergence. Central NC is situated at the southern periphery of the westerlies, in SW flow aloft. Upper level forcing will be limited to small amplitude waves in SW flow aloft and confined to W/NW portions of the state. 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). With the above in mind, expect convective coverage to be greatest in the 18-03Z across portions of the Sandhills/SW Piedmont where destabilization will be greatest invof the boundary, and in the far W/NW Piedmont where episodic DPVA will augment forcing and offset weaker instability. 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/... As of 250 AM Monday... Continued damp with a volatile air mass. Moisture will steadily deepen with increasing surface dewpoints, resulting in slightly higher MUCAPE by Tue afternoon. Mid level flow remains weak from the W or WSW, with little agreement among the models as to where minor perturbations might track. The NAM, which did the best in detecting the convective complex over the OK/TX border early this morning, is the only large scale model that retains its resultant MCV and has it approaching NW NC late Tue into Tue night. But even then, it`s hard to have confidence in tracking a feature in flow this weak. And with the column becoming so damp, it won`t take much to prompt precip. As the models develop areas of showers and storms aligned with subtle boundaries and outflows with little spatial agreement among them, forecast uncertainty rises, with convective details difficult to pinpoint with confidence. Will start out with low chance pops in the morning, increasing to likely areawide (with PW projected to reach well above 2.0") from midday through the mid evening before trending pops downward NW to SE, as models show a weak surface trough tracking ESE through central and eastern NC overnight. Highs 83-90 and lows 69-75. -GIH && .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 1100 AM Monday... 24-hr TAF Period: LIFR/IFR ceilings are expected to improve to IFR/MVFR by early-afternoon. Improvement to VFR will be possible by mid-afternoon at the FAY terminal, however, MVFR ceilings are expected to persist longer at northern terminals, especially INT/GSO. Adverse conditions assoc/w convection will be possible at all terminals this aft/eve, with the relative best chance at the INT/GSO/FAY terminals. With little change in pattern/airmass, IFR/LIFR ceilings are expected again at all terminals late this evening/overnight. 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...Hartfield LONG TERM...KC AVIATION...Vincent

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