Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 090208 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 910 PM EST Thu Dec 8 2016 .SYNOPSIS...
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A strong and cold high pressure centered from Alberta Canada into the northern Plains will continue building SE toward NC through Saturday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 910 PM Thursday... Cold air advection continued over NC this evening as arctic surface high pressure builds in from the NW. The jet level cloudiness continued to shift east and was slowly thinning out as well. In general, the skies were mostly clear to partly cloudy at mid- evening. The skies are expected to become clear by morning. The pressure gradient that is tight will remain so overnight which would normally keep the winds up. In this case, with the center of the high pressure so far to our NW (Alberta/Saskatchewan), winds will at times die off to nearly calm in the NW flow. The dew points were already in the single digits and teens over the NW Piedmont, ranging into the 20s SE Coastal Plain. The occasional breeze to 10 mph should keep the temperatures up somewhat even with the CAA. Lows 25- 30 NW to SE for the most part expected.
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&& .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/... 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 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett/Smith NEAR TERM...Badgett/Smith SHORT TERM...Smith LONG TERM...MWS AVIATION...KC/Smith

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