Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270829 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 425 AM EDT Tue Jun 27 2017 .SYNOPSIS... A moisture-starved cold front will cross NC today. Canadian high pressure will follow and crest over the southern middle Atlantic states Wed and Wed night. && .NEAR TERM /TODAY/...
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As of 400 AM EDT Tuesday... Mid and high cloudiness will become thicker and more widespread today as an upper short wave and associated surface cold front move east across the area. Moisture depth is shallow but a narrow zone where low level convergence and mid level support coincide will produce a few showers in the west this morning, with low chance PoPs shifting east by around mid day. Diurnal cycle will have time to build weak instability in the east(~500 joules MLCAPE), so an isolated storm is possible. MOS and thicknesses support slightly warmer temps than previous runs and will make a very minor tweak upward in response as the thickening cloud coverage and virga will be pulling in the other direction. Highs will range from ~80 northwest to as high as 87 in the southeast.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
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As of 400 AM EDT Tuesday... The system will be east of the area by early tonight with decreasing cloudiness leading to mostly clear skies after midnight as high pressure builds in from the northwest. Mins will tumble in the drying airmass with the clearing above, and most areas should be in the upper 50s by sunrise Wednesday. Skies will remain clear through Wednesday night as the high moves across the area, with highs Wednesday edging up a bit under strong sun to reach the low and mid 80s, with mins Wednesday night in the lower 60s.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... As of 350 AM Tuesday... Initially zonal flow aloft, around the nrn periphery of a developing/strengthening sub-tropical ridge centered over the wrn N. Atlantic, will yield to (generally weakly) perturbed swly flow aloft as a trough aloft now over wrn Canada amplifies across the central U.S. The most notable (synoptic-scale and predictable) of these disturbances in swly flow aloft will be a s/w trough now crossing TX, which the models indicate will meander briefly over the nwrn GOM before lifting newd across the Sern U.S. and Carolinas Thu-Fri. At the surface, high pressure will drift across and remain over the central N. Atlantic through early next week. Return flow around the high will yield gradually increasing temperatures and humidity levels, marked most abruptly by the passage of a warm front on Fri, followed by a peak in the humidity this weekend and the heat Mon and Tue. Despite mid level warmth associated with the sub-tropical ridge, and resultant weak mid level lapse rates, the aforementioned warming and moistening low levels should prove sufficient for at least scattered diurnal convection throughout central NC during the upcoming holiday weekend, after which time, a sharpening Appalachian- lee trough and mixing out of surface dewpoints to the west will probably shift the focus for convection over the ern half or third of the forecast area. && .AVIATION /06Z Tuesday through Saturday/... As of 155 AM Tuesday... The approach of a mid-upper level disturbance and associated surface cold front will result in patchy mid-high level cloudiness today. Moisture will be in short supply, and while we may see a few showers, coverage is expected to be too low to include in the TAFS. Winds will shift to northerly at 6-8 knots this morning as the surface front moves southeast across central NC, reaching the coastal plain around mid day. High pressure will settle in behind the exiting disturbance tonight and linger through Thursday. As this high exits offshore Friday, the return southerly flow will advect a moist unstable air mass into our region, setting the stage for scattered afternoon-evening convection, and early morning low clouds and fog. Thus, the potential for periods of MVFR/IFR parameters will increase, beginning Friday morning and continuing into the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...mlm SHORT TERM...mlm LONG TERM...MWS AVIATION...mlm/CBL

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