Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220248 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1040 PM EDT Sat Jul 21 2018 .SYNOPSIS... A mid and upper-level low across the Ohio Valley will move slowly south across the southern Appalachians into the middle of the work week. A deep, moist, southerly flow will extend across the Carolinas through much of the work week. && .NEAR TERM /THROUGH TONIGHT/... As of 1040 PM Saturday... Scattered showers and thunderstorms continue to develop and shift east across portions of western and central NC late this evening. The convection is being driven in part by an eastward advancing shortwave trough across northwestern NC and and western VA that is visible on the 1.5 PVU surface with another trough noted across northeast GA. These features will pivot northeast around the upper trough overnight. The air mass across much central NC can be characterized as weakly to moderately unstable with MLCAPE values of 500 to 1200 J/Kg. The GSO RAOB notes that the mid-levels have cooled around 3 deg C at 500 MB since 12Z this morning. Given the appreciable forcing across the area tonight, scattered showers and thunderstorms are expected to move across the area overnight with the last batch of storms likely to move across the Sandhills/eastern Piedmont into the Coastal Plain between 4 and 8 am. DCAPE values over 900 J/Kg extend in a south to north axis across the Sandhills into the eastern Piedmont late this evening along with 0-6km bulk shear of around 30 kts in the south will support a limited severe weather threat into the early morning hours, mainly to the south and southeast of Raleigh. Low temperatures by Sunday morning will range in the upper 60s north to lower 70s south. -Blaes && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 330 PM Saturday... The day should start of quiet with subsidence behind tonight`s short wave and convection. Then as the day progresses and the closed mid- level low over the Ohio Valley drifts south, we may see another round of showers and thunderstorms develop to our west over the mountains and move east into our western zones during the late-day or evening period. In terms of temperatures, we should see more sunshine on Sunday compared to today given that the coastal system will be gone and given aforementioned early-day subsidence over our area, thus look for highs climbing into the mid to upper 80s. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 330 PM Saturday... A piece of the closed mid-level low is progged to break off and slowly drift into deep south region, resulting in a long fetch of deep moist south to southeasterly flow to become established over central and eastern NC beginning Monday and lingering perhaps into Wednesday, before the closed low begins to open up and lift toward the northeast during the late-week period. The end result will be unsettled, to perhaps wet weather right through the long term period. Temps during this time will be dependent on whether any breaks in the rain/clouds happen, so for now, will stay close to climo, or perhaps a few degrees below climo. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... As of 845 PM Saturday... A strong upper level disturbance will lift newd across the srn Appalachians and Carolinas tonight, where it will interact with a surface frontal zone draped at 00Z from near EXX to FAY to PGV. A weak frontal/surface low and related compact cluster of showers and storms will likely develop and track newd across cntl NC tonight, thereby causing initially VFR conditions to become sub-VFR as the convection moves overhead. Additionally, patches of mainly MVFR ceilings may develop along and north of the front, including at all of the cntl NC TAF sites, late tonight and early Sunday. A risk of an MVFR ceiling will then persist through around 16Z, after which time cloud bases will have lifted and/or scattered to VFR range. While scattered showers and storms are expected again Sunday afternoon and evening, confidence in timing and location precludes inclusion in the TAFs at this time. Outlook: Moist and perturbed sly deep layer flow will result in an above average chance of showers and storms, and late night-early day sub-VFR ceilings, through the middle of next week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Blaes NEAR TERM...Blaes SHORT TERM...np LONG TERM...np AVIATION...MWS

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