Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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603 FXUS62 KRAH 082312 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 612 PM EST Thu Dec 8 2016 .SYNOPSIS... In the wake of a cold front moving offshore, an expansive arctic high will dominate through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 310 PM Thursday... Cold advection has ensued in the wake of a cold front that finally pushed east across the area earlier this morning, with a northwest wind gusting to 15-20kt at times. Temps have only risen a few degrees, if any, owing to the cold advection and a veil of mid and high clouds. A few radar echoes continue to race northeast across the Piedmont and Coastal Plain, but with dewpoints crashing into the 20s and 30s, this is likely all virga. Cold advection will continue tonight as the pressure gradient briefly tightens in response to an expansive 1040mb high building out of the northern Plains. Meanwhile, skies will clear as upper jet to our northwest shifts east, resulting in lows in the mid to upper 20s, per model consensus. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 310 PM Thursday... Arctic high pressure will build east toward the Tenn Valley Friday and Friday night, keeping central NC int he cold advection regime for another day. The pressure gradient will relax a bit, with forecast soundings only showing 15-20kt of wind in the boundary layer, though some slightly stronger gusts are possible at the onset of mixing mid-morning. Otherwise, skies will be clear and MOS guidance products are in good agreement on mostly lower 40s for highs. The surface high will nudge eastward Friday night, though it won`t quite settle overhead. The pressure gradient should be weak enough, however, for decoupling (especially west) and a 1270m thickness supports highs in the lower 20s, with teens in outlying areas. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 310 PM Thursday... The medium range models are in good agreement with the migration of ~1035 mb modified arctic high pressure across the Central Appalachians and Middle Atlantic states Sat and Sat night. Cold temperatures --10-15 degrees below average-- will result, with highs 40-45 and lows in the lower to middle 20s. Aside from cirrus, some of which may become briefly orographically-enhanced over the wrn Piedmont early Sat, the column will otherwise remain dry/clear. A Pacific shortwave trough, embedded within fast and broadly cyclonic flow across much of the Lower 48, will support a migratory wave of low pressure from the TX panhandle Sun to the Nrn Appalachians Mon. A preceding warm/coastal front will retreat Nwwd across central NC with an associated chance of showers during that time (Sun-Mon). Temperatures will moderate with the retreat of the warm front, and clouds. The trailing cold front, and continued chance of showers, will follow and cross NC late Mon-early Tue. Uncertainty in the mid to late week forecast remains above average. There are indications that a flat frontal wave will zip off the SE U.S. during the middle of the week; and this feature may spread a shield of light rain across NC late Tue-Wed. Thereafter, the models continue to indicate another cold frontal passage and associated arrival of colder temperatures will occur by Wed night-Thu, but recent model runs have backed off somewhat on how far S the next dome of arctic air will plunge. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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As of 610 PM THURSDAY... 24-Hour TAF period: High confidence that VFR conditions will prevail through the TAF period. Winds will be northwesterly, generally 5-10 mph overnight, increasing to around 10 mph with gusts of 15-20 mph in the afternoon. Some lingering high clouds will gradually clear overnight. -KC Looking ahead: VFR conditions are expected through the weekend. There is a small chance of sub-VFR ceilings on Sunday, with better chances Monday and Thursday. -Smith
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Smith NEAR TERM...Smith SHORT TERM...Smith LONG TERM...MWS AVIATION...KC/Smith

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