Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 241052 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 652 AM EDT Tue Apr 24 2018 .SYNOPSIS... An area of low pressure will track northeastward across the Carolinas and VA through tonight. A weak cold front will then cross our region late Wed and Wed night. && .NEAR TERM /THROUGH TONIGHT/... As of 415 AM Tuesday... WV imagery this morning depicts a parent mid-upr lvl low over w-cntl KY/TN, with a pair of preceding srn stream perturbations over ern GA and SC. The lead perturbations will pivot newd, in increasingly negative tilt fashion, across cntl NC between 12-18Z, then to the nrn middle Atlantic coast by this evening. The parent mid-upr low will then wobble ewd across the srn/cntl Appalachians tonight, to the wrn NC Piedmont by 12Z Wed. Between the lead srn stream perturbations and the parent mid-upr low, a mid level dry slot will nose across the Carolinas this aft-eve. In the lwr levels, strong low lvl warm and moist advection/ isentropic upglide --courtesy of a 40-50 kt sely low lvl jet-- will support ongoing widespread low overcast and rain this morning, the latter of which is forecast to pivot newd with the migration of the low level jet through midday-early aft. Upstream hourly rainfall amounts over SC and sern NC have increased to around a quarter to half inch this morning, and similar rates will likely result in another one to two inches of rain focused over the Sandhills and srn and cntl Coastal Plain as the warm conveyor precipitation migrates newd - short of 3-hr flash flood guidance values of 2.5 to 3.5 inches there. At the surface, a 1010 mb surface low just east of Atlanta at 08Z will track slowly newd through the w-cntl Carolinas and cntl VA through tonight. A warm front preceding the low was analyzed at 08Z from the low ewd to the s-cntl SC coast (near CHS); and this warm front is forecast to retreat nwd into srn and s-cntl NC by 18Z. Associated scattering of the earlier low ovc will support weak to moderate destabilization as an increasingly moist warm sector, characterized by surface dewpoints mainly in the lwr 60s, diabatically warms into the 70s. Meanwhile, a lingering cooler and more stable regime north of the warm front will favor highs between 60-65 degrees over the nrn Piedmont. Scattered convection is expected to redevelop, likely in low lvl confluence bands on the ern periphery of the surface wave, then track nwd into srn-cntl NC this aft. Low lvl and deep layer flow will have weakened considerably and veered in the wake of the early day WAA/isentropically-driven rain, though lingering effective SRH on the order of 100-150 m2/s2 in the vicinity of the warm front may support episodic low level rotation in those convective bands, particularly as they track near and across the slowly nwd-retreating warm front. An isolated tornado or damaging wind gust will be possible with any such activity, with the relative highest probability in a corridor from VUJ to TTA to RWI/nearest the warm frontal position. Showers will linger, or more likely redevelop late tonight over the wrn Piedmont, as the mid-upr low and associated cold pool aloft pivot overhead. Lows in the 50s. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... As of 415 AM Tuesday... An active, energetic upper pattern featuring a long wave trof over the eastern CONUS will persist from mid week into the early weekend. An initial stacked low pressure system and associated surface low will lift northeast up the coast on Wednesday with lingering scattered showers, mainly across the northern tier of central NC. A dry backdoor cold front will be pushed south into the area on Wednesday night in the wake of this initial system. Highs on Wednesday will be in the low to mid 70s, cooling a couple of degrees on Thursday to the upper 60s to lower 70s. A second, vigorous short wave system will migrate east into the Tennessee Valley late Thursday, where it will phase with and lift a surface low over the Gulf States northeast across the area Thursday night. This system will feature strong low level convergence from the surface system in conjunction with decent mid level support due to steep mid level lapse rates accompanying the short wave. Will continue chance category PoPs maximized Thursday night for now with an eye on ramping up coverage and potential thunder as details become more certain. Highs on Friday will range from 70 to 75. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 335 AM Tuesday... The primary long wave upper trof will be edging east, with the trof axis passing over the area on Saturday, possibly squeezing out a final few showers during the morning. Highs Saturday will be in the upper 60s to lower 70s. Heights finally begin to build late in the weekend as upper ridging moves into the Midwest, with strong sunshine as the associated surface high builds over the area. Highs Sunday will be in the low to mid 70s, with mid and upper 70s expected on Monday. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 650 AM Tuesday... Widespread rain, and IFR-MVFR conditions, will pivot northeastward across cntl NC early today. A warm front will then retreat nwd into srn and cntl NC this afternoon; and this will result in a lifting and scattering of the low ceilings to VFR at FAY around 18Z, with subsequent destabilization and threat of a strong to severe thunderstorm this afternoon. The warm front and brief scattering to VFR may edge as far nwd as RWI and RDU between 19-22Z, while INT and GSO are likely to remain in a cooler and saturated, cold air damming and IFR regime, throughout the TAF period. While the highest probability of a storm will be at FAY, a few elevated rumbles of thunder will be possible throughout cntl NC today, and again late tonight-early Wed, as an upr lvl low and associated pocket of cold temperatures aloft drift overhead. Otherwise, strong easterly winds will maintain breezy conditions through this afternoon, before subsiding by this evening. Outlook: A low lvl deformation band of MVFR ceilings will pivot ewd across cntl NC early Wed. VFR conditions are otherwise expected until another upper level trough and period of unsettled weather (threat of rain and sub-VFR conditions) spread east across cntl NC Thu night into Fri.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...MLM LONG TERM...MLM AVIATION...MWS is the U.S. government's official web portal to all federal, state and local government web resources and services.