FXUS62 KRAH 090208

Area Forecast Discussion
National Weather Service Raleigh NC
910 PM EST Thu Dec 8 2016

A strong and cold high pressure centered from Alberta Canada into
the northern Plains will continue building SE toward NC through


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.


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


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.


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





NEAR TERM...Badgett/Smith

NWS RAH Office Area Forecast Discussion