Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181326 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 926 AM EDT Tue Jul 18 2017 .SYNOPSIS... An upper level low will drift slowly east across NC and VA through Wed. Hot and mainly dry sub-tropical high pressure will otherwise expand from the central U.S. to the Carolinas through the weekend. && .NEAR TERM /THROUGH TODAY/... As of 355 AM Tuesday... Persistent shear axis and moisture plume will again stack higher chances of convection towards the southeast today. A short wave trof will be edging east over the area, which will provide better support for convection with good diffluece aloft along I95 as a 60kt jet in the lee of the trof lifts into the mid Atlantic. Widespread cloudiness will aid in suppressing temps a bit, with upper 80s in the offing for most of the area this afternoon. PoPs in the chance range look good, and may need to raise them across the area a bit if morning low cloudiness burns off quickly this morning to allow instability to ramp up more quickly. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... As of 355 AM EDT Tuesday... The upper trof cuts off and wanders very slowly across the area through the mid week. Chances of convection will be favored on the east side of the cutoff, but moisture availability will be reduced as the moisture plume which was lying along the coastal plain is pushed offshore tonight. As such, will have small chance of convection overnight, ramping up to 30% in the east on Wednesday afternoon, and falling off the radar scope Wednesday night as subsidence settles in behind the cutoff. Mins tonight and Wednesday night will be persistence in the unchanged airmass...70-ish. Highs on Wednesay should be pretty uniform across the area due to heavier cloudiness in the east...90 to 92...maybe stalling in the upper 80s in the east if rain is more widespread than currently forecast. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 355 AM Tuesday... A mid-upper level evolving now over the middle Atlantic states will move slowly east, to just off the sern NC coast by 12Z Thu, before drifting swwd along the sern U.S. coast and to near the FL panhandle by Sat. This is a change in model run-to-run continuity from previous days, which indicated the low would move off DelMarVa and out to sea through the end of the week. The retrogression of this feature would occur in a break, or weakness, in a pair of sub- tropical ridges that will otherwise span from the central Plains/mid MS Valley to the wrn N. Atlantic, and may result in slightly less hot conditions than earlier forecast, particularly along the sern U.S. coast where a relative minimum in heights/thicknesses would result. At the surface, a trough will become established in the lee of the srn and central Appalachians, on the wrn periphery of high pressure over the central and wrn N. Atlantic. The presence and influence of the sub-tropical ridge will likely restrict diurnal convection to differential heating zones over the mountains and along the sea breeze. Despite the possibility of the slightly less hot temperatures noted above, heat and high heat indices may yet become hazardous, as temperatures beneath the ridge climb into the middle 90s to around 100 degrees - hottest Fri-Sat. When combined with surface dewpoints ranging from the middle to upper 60s west of the Appalachian-lee trough (over the nw NC piedmont) to lower to middle 70s to the east of that feature (over the Coastal Plain), heat index values between 100 and 110 degrees are expected to result. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 140 AM Tuesday... 24 hour TAF period: Extensive high cloudiness will delay fog/stratus development until just prior to sunrise - similar to last night. Light flow will prevent denser fog, so visibility will remain MVFR, while IFR ceilings are possible in the 10-14Z time frame, especially in the east - RWI/FAY. Scattered convection is expected...again mainly in the east...by mid to late morning as a mid level trof moves into and stalls over central NC. Confidence in coverage and timing is not high enough to include in the details of the TAFs. Long term: Day and evening showers and storms will be possible again on Wednesday along with the possibility for fog/low stratus in the morning. Then rain chances will decrease for the latter half of the week with generally VFR conditions expected. && .CLIMATE...
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RDU Records: Date | High Year | High Min Year ------------------------------------------ 18 July | 103 1887 | 79 1887 19 July | 101 1902 | 80 1942 20 July | 102 1942 | 76 1981 21 July | 102 2011 | 78 1932 22 July | 103 2011 | 78 2011 23 July | 105 1952 | 78 2011 24 July | 101 2011 | 79 2011 GSO Records: Date | High Year | High Min Year ------------------------------------------ 18 July | 97 1986 | 76 1986 19 July | 98 1977 | 75 2016 20 July | 100 1977 | 75 1986 21 July | 102 1926 | 76 2011 22 July | 101 1926 | 77 2011 23 July | 99 1952 | 78 2010 24 July | 99 1914 | 78 2010 FAY Records: Date | High Year | High Min Year ------------------------------------------- 18 July | 103 1942 | 76 2013 19 July | 101 2002 | 77 1988 20 July | 104 1932 | 80 1996 21 July | 105 1932 | 89(?) 1944 (we are checking on this) 22 July | 107 1932 | 79 2011 23 July | 103 2011 | 79 1998 24 July | 105 1952 | 79 1945
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MLM SHORT TERM...MLM LONG TERM...MWS AVIATION...MLM CLIMATE...RAH

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