Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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852 FXUS62 KRAH 211632 AFDRAH AREA FORECAST DISCUSSION National Weather Service Raleigh NC 1230 PM EDT Sat Sep 21 2019 .SYNOPSIS... High pressure will extend from the southeastern US to Bermuda through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 940 AM Saturday... Forecast remains on track this morning. Temperatures have been quicker to rise compared to previous mornings, which bodes well for the high temperature forecast (middle 80s) today. Previous valid discussion... 00Z upr air data indicate the mid lvl/subtropical ridge has strengthened and drifted east/become centered across the TN Valley/srn Appalachians. Meanwhile in the upr lvls/at the tropopause, a perturbation evident over OH/IN in WV satellite imagery this morning will shear ssewd across the cntl Appalachians and srn middle Atlantic states through this evening, then offshore. Thin cirrus will accompany this feature, while a scattering of cumulus will otherwise focus over the nrn and nwrn Piedmont, where 850-925 mb moisture will remain relatively maximized. At the surface, high pressure analyzed over ern NC at 08Z will drift offshore while continuing to extend wwd into the sern US today, with an Appalachian-lee trough that will strengthen with diurnal heating. While it will remain dry in cntl NC, isolated to widely scattered showers will be possible along both the lee trough, mainly over the Foothills, and also in the mountains. Occasional swly stirring between the lee trough and the offshore ridge may marginally hinder otherwise strong radiational cooling conditions tonight, with lows in the mid 50s to lwr 60s. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 355 AM Saturday... Under the continued influence of a strong subtropical ridge centered over the srn Appalachians, the forecast will be a generally persistence to slightly warmer one. Mostly sunny/clear conditions should persist, with highs in the mid-upr 80s and lows around 60 degrees. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 425 AM Saturday... The extended forecast has remained in fairly good agreement over the last couple of days with the big picture as near normal heights are expected through Wednesday with mid-level ridging quickly intensifying Thursday into Friday. The GEFS, GEPS, and EPS are in very good agreement here with above normal temperatures and below normal precipitation expected through the period. Monday an upper level low will be crossing the Great Lakes region with the subtropical ridge flattening. Ahead of the upper level low 850 mb flow will turn from the west allowing 1000/850 mb thicknesses to surge towards 1415 m. Forecast soundings on Monday show deep mixing with a DALR in place through 850 mb. Highs should easily reach the upper 80s Monday afternoon with 90 degrees possible towards the Sandhills. Monday night into Tuesday morning a surface cold front will cross into central NC and now looks to clear all zones Tuesday afternoon into evening. The GFS remains slower than the ECMWF and CMC with the frontal passage Tuesday, and continues to fracture the baroclinic zone over SC. Both the ECMWF and CMC has the front clearing central NC Tuesday morning and have kept the forecast trended this direction. The other question remains whether or not precipitation will be seen with the frontal passage. The best dynamics (associated 500 mb height rise/fall couplet) with the upper level low remains over New England while surface convergence is weak. The main factor here appears to be the apparent lack of moisture. PWATs ahead of the front are forecast to be around 0.8" with substantial dry air located near the surface and between the 600/800 mb layer. Latest run of the NAM is showing enough air mass moderation for some virga possible across the northern zones. For now have kept the forecast dry, but this might need to be changed in future forecast packages. Tuesday into Wednesday temperatures will remain above normal with highs averaging in the mid 80s area wide, but dewpoints will only be in the 50s which will help keep the heat index in check. By Thursday though the frontal zone, or whatever is left of it, will head north into VA with dewpoints recovering into the mid 60s. High temperatures will also start to quickly rebound Thursday as mid-level ridging begins to take shape across the southeastern United States. 1000/850 mb thicknesses Thursday rise to around 1425 m with highs near 90 degrees expected area wide. Towards the end of the extended mid-level heights continue to slowly rise, with a back door cold front possible. Latest run of the GEFS continues to show some skewness towards the warmer temperatures so have kept the forecast trended this direction. && .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/... As of 1230 PM Saturday... VFR conditions expected to continue over the next 24 hours with high pressure remaining in control. Light southerly to southwesterly flow will continue as the center of the high remains just east off the Carolina Coast through tonight. Some upslope showers/storms formation east of KINT/KGSO will be possible this afternoon and evening, however, coverage east of the Blue Ridge will remain little to none. Overnight, winds calm as the atmosphere decouples quickly. Can`t rule out some isolated MVFR fog/stratus development across the area, however, coverage should remain isolated at best. Have included mention at KRWI only at this time. Outlook: Pockets of MVFR/IFR fog will remain possible across the eastern terminals through Monday, otherwise, high pressure will continue to yield predominant VFR conditions. A mostly dry cold front crosses the region from northwest to southeast Monday night with high pressure filling back in through the middle of the work-week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...JJM/MWS SHORT TERM...MWS LONG TERM...Haines AVIATION...JJM is the U.S. government's official web portal to all federal, state and local government web resources and services.