Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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477 FXUS62 KRAH 271423 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1020 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/... As of 1020 AM EDT Tuesday... Just minor adjustments required to the near term forecast, primarily to decrease PoPs in the west and tweak temp/dewpoints as temperatures are averaging 2-3 degrees warmer than expected. 12Z upper air analysis depicts a modest mid-level trough exiting the TN Valley this morning. This feature accompanied by 30-40m height falls. While synoptic lift present, atmosphere over central NC not all that moist, and minimal moisture advection noted in the analysis. Still expect the highest coverage of a few showers and possibly an isolated t-storm to occur this afternoon-early evening across the eastern and southern sections of our forecast area. The threat for showers does not look all that impressive across the western Piedmont so have lowered PoP a bit in this region. Early morning dewpoints were in the upper 50s to lower 60s. As mixing ensues late morning-early afternoon, expect dewpoints to drop into the low-mid 50s most places. Mid-morning temperatures have warmed into the low-mid 70s. Temperatures should slow their rise as mid/upper level clouds thicken this afternoon. Still expect enough heating to warm into the low-mid 80s. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... 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. && .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 /14Z Tuesday through Saturday/... As of 1020 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. Sfc winds will veer to a nly direction with speeds less than 10 kts. 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...WSS SHORT TERM...mlm LONG TERM...MWS AVIATION...WSS

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