Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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368 FXUS62 KRAH 241937 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 337 PM 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 cross our region late Wed and Wed night. && .NEAR TERM /THROUGH TONIGHT/... As of 1100 AM Tuesday... 12Z upper air analysis depicts a mature cyclone over the TN Valley with a mid/upper level s/w emanating from the low sewd into the Savannah River Valley. A reflection of this s/w is depicted at 850mb by a trough situated along the SC/NC border. Low level sely fetch ahead of the 850mb trough transporting abundant moisture into central NC. This moisture being lifted by the approaching low-mid level trough, with additional lift supplied by a 250mb 90kt jet lifting nwd over the central Appalachians. Through 18Z, appears the bulk of the rain showers will occur north and east of Raleigh, where hourly rates of a tenth to two-tenths of an inch will be common. This should lead to storm totals between one and two inches in this region, matching the numbers reported early this morning from the southern and western sections of the forecast area. The focus for scattered convection will be primarily across the southern Piedmont into the Sandhills later this afternoon and early this evening. A warm front, currently residing roughly west-to-east across South Carolina, projected to lift nwd into our southern counties this afternoon in conjunction with a sfc wave currently located near/south of Greer, SC. While the better kinematics will be pulling away from our region, there should still be enough shear to aid in the development/maintenance of isolated strong/severe convection late this afternoon through sunset. While the main severe weather hazard will be locally strong/damaging wind gusts, an isolated weak tornado cannot be ruled out, especially with any cell in vicinity of the warm front where the 0-1km storm relative helicity will be maximized. Timing still favors the mid/late afternoon until sunset, or roughly 3 PM-8 PM. There is the possibility that destabilization in the lower levels will be halted/minimized by thick overcast maintaining its presence longer than expected. If this occurs, the already small threat for isolated severe will become remote. Temperatures this afternoon will vary widely across the region, ranging from the lower 60s in vicinity of the Virginia border to the low-mid 70s across the far south. Its possible that cooler temperatures will occur across the south half if the warm front fails to move as far north as expected. Tonight, the upper level low will migrate ewd into NC. This system will maintain a few showers into the overnight across the western and southern Piedmont. Locations roughly east of highway 1 should get a chance to dry out after midnight. Min temps mainly in the mid- upper 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 /THURSDAY THROUGH MONDAY/... As of 335 PM Tuesday... As the mid- upper-level low lifts off to the northeast and gets absorbed into the low over the Great Lakes there will be a brief lull in precipitation chances over Central NC Thursday morning into Thursday Afternoon. Another shortwave low aloft will swing through the the Deep South and toward the Mid-Atlantic coast Thursday resulting in another chance for showers and thunderstorms across the region Thursday aft/eve into the overnight hours. As that second shortwave low moves through the area, a third shortwave will dive south through the ARKLATEX, elongating the parent longwave trough aloft. This third low may result in additional precipitation over the Carolinas, however there are some model differences in that regard at this time. Will continue to carry at least a slight chance for rain through Friday night, but confidence in rain occurring is not terribly high at this time. Meanwhile at the surface, a low will drift north-northeastward out of the Deep South and along the Eastern Seaboard toward New England. Temperatures Thursday through Saturday: Highs ranging from around 70 degrees in the NW to mid 70s SE and lows decreasing from mid 70s Thursday night to mid 40s NW to around 50 degrees SE Saturday night. Largely expect Sunday and Monday to be dry with highs in the low to mid 70s and lows in the mid 40s to low 50s. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 140 PM Tuesday... There is high confidence that adverse aviation conditions will persist across central NC through Wednesday morning with widespread MVFR/IFR ceilings expected through 02Z Wednesday. After 02Z, widespread LIFR/IFR ceilings should dominate. Scattered showers and an isolated thunderstorm or two will occur through early evening, primarily across the Sandhills, and the southern and western Piedmont. After sunset, scattered showers will continue to plague the western Piedmont, including the Triad terminals. Elsewhere, only isolated showers expected with patches of MVFR/IFR fog developing overnight. After 14Z Wednesday, expect to see ceilings slowly lift with MVFR/low end VFR ceilings expected by 18Z-20Z. MVFR conditions due to areas of fog and ceilings anticipated for Wednesday night. The adverse aviation conditions expected to persist through the end of the work week and possibly into Saturday. Improving aviation conditions and a return to widespread VFR parameters forecast for Sunday. && .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...MWS NEAR TERM...WSS SHORT TERM...MLM LONG TERM...KC AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.