Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211922 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 322 PM EDT FRI OCT 21 2016 .SYNOPSIS... An upper level trough and attendant cold front will track east across the Carolinas this evening. A cooler and drier airmass will advect into the region from the northwest in the wake of the front tonight and Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 320 PM Friday... Strong forcing in the form of of 120m-180m height falls (170m at BNA this morning) and intense FGEN showing up from 925mb through 700mb, courtesy of a deep upper trough swinging through the Ohio/Tenn Valley and a cold front near the US-1 corridor, coupled with up to 500 j/kg of warm sector MLCAPE, has lead to a very recent formation of a broken band of convection. Moisture is limited, per water vapor imagery, but the aforementioned forcing, 40-50kt mid-level flow, and increasing DCAPE (~800 j/kg, may support some strong winds with the heaviest shower or a few isolated storms, mainly from Fayetteville to Rocky Mount and east. Behind the front, winds are northwest winds are starting to gust a little, mostly 17-22kt, and this should continue into the evening hours as cold advection ramps up. Rap soundings show a bit of a surface inversion by midnight, so gusts should abate despite the cold advection, with lows ending up in the mid to upper 40s. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 320 PM Friday... Thicknesses crash to ~1330m tonight, with very little recovery on Saturday as cold advection continues. Dry adiabatic mixing to 850mb yields upper 50s to mid 60s, with clear skies and a 10-15mph northwest wind that will gust to 20-25mph. Winds will again weaken Saturday night, possibly enough so to decouple across the southern and western Piedmont as high pressure builds in from the southwest. Areas that decouple will see lows in the upper 30s given thicknesses again below 1340m, with low/mid 40s elsewhere. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 230 PM Friday... Dry weather is expected for the end of the weekend through the middle of the upcoming work week. The general weather pattern during the extended period will feature an exiting high amplitude upper trough early Sunday followed by rising heights and a dry northwest to west-northwesterly flow through late Wednesday with a dry cold front dropping across the region on Monday. A short wave ridge will move across the region on Wednesday night as troughing approaches the Appalachians on Thursday and moves offshore on Friday. The sensible weather will feature dry weather through the period with near zero PoPs through early Wednesday night. After a chilly start to the weekend, temperatures will moderate on Sunday and especially Monday. Have adjusted maxes up a degree or two on Sunday and several degrees on Monday. Even though a cold front will move across the area on Monday, it appears the cold advection will lag the fropa in central NC allowing temperatures to moderate. The 10/21 00Z ECMWF ensemble guidance for RDU has a mean of 77 on Monday, the warmest has 80, coolest has 72, and the operational ECMWF has 75. Worth noting that consensus 1000- 850 thickness values jump from Sun to Mon and range between 1365 and 1375m on Monday morning. Temperatures cool down a bit behind the front on Monday night through Tuesday night. Some uncertainty arrives for the end of the period as two northern stream waves drop into the western Great Lakes on Thursday and shift east on Friday. The 12Z GFS and ECMWF have come into better agreement and suggest some slight chance PoPs are warranted for Thursday night and early Friday across the north and northwest. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... As of 145 PM Friday... A narrow band of moisture accompanying a cold front crossing the area should lead to a band of showers and perhaps an isolated storms this afternoon, mainly east of RDU toward FAY and RWI BETWEEN 18z AND 21z. MVFR ceilings and wind gusts to 25-30kt will be possible with the showers, and a winds will shift to northwesterly behind the front at 12-15kt gusting to near 25kt. Winds will weaken and become less gusty this evening, but should stay between 5-10kt out of the northwest, with otherwise clear skies and VFR. Looking Ahead: Breezy NW winds will redevelop on Saturday, sustained at 10-15 kt with gusts up to 20-25 kt, becoming westerly and weakening Saturday night and Sunday. VFR conditions are expected to rule for the remainder of the weekend and through the majority of next week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...VINCENT NEAR TERM...SMITH SHORT TERM...SMITH LONG TERM...BLAES AVIATION...SMITH is the U.S. government's official web portal to all federal, state and local government web resources and services.