FXUS62 KRAH 111731 RRA

Area Forecast Discussion
National Weather Service Raleigh NC
1230 PM EST Mon Dec 11 2023

A strong cold front will push off the North Carolina coast this
morning. Behind the front, surface high pressure will build into the
Southeast today through Tuesday. A dry secondary cold front will
cross the area early Wednesday, and will be followed by another high
pressure area late Wednesday into Friday.


As of 940 AM Monday...

With the morning update, needed to increase sky cover across both
the northwest and southeast portions of the forecast area. Lower
clouds have held on a bit longer than expected, and the new forecast
may still be a little optimistic when it comes to clouds clearing
out. Made some minor tweaks to hourly temperatures, and overall
reduced highs by a couple degrees in the locations with cloud cover.
Previous discussion follows.

As of 255 AM Monday...

The strong cold front has pushed just E of the forecast area in the
last hour, designated by a sudden wind shift and sharp drop in temp
and dewpoint (as much as 10-15 deg F in around 10 min). The heavier
showers persist just behind the front, noted by cool cloud tops and
a period of enhanced gusts up to 30-40 mph, although the deepest
convection has blossomed off the Carolina coast (and this is on
track to pass over the Outer Banks in the next several hours).
Trailing stratiform rain extends back through the E Piedmont and
Sandhills at this hour, having exited the W Piedmont. (The threat of
a little wet snow mixed in at the end is not zero but is low in our
area, as we're likely to see drying in the mixed phase region aloft
prior to temps dropping into the mid 30s or lower, meaning little to
no ice in the cloud.) Satellite imagery and surface obs show strong
gravity wave action behind the front (the saturated stable layer
conducive to ducting is depicted on the 00z FFC sounding at 850-600
mb), and this has led to a period of surface winds over the Piedmont
from the NE (when CAMs suggest we should be seeing NW winds). The
potent mid level shortwave trough and strong upper level divergence
helping to support the post-frontal rain will continue a gradual
eastward shift, with a clearing-out of both low and mid level
cloudiness from W to E through daybreak, although the Coastal Plain
may retain some clouds through mid morning. Surface high pressure
will build into the Southeast from mid-late morning through tonight,
and as we'll be on the subsidence side of the mid level wave, skies
will be generally clear. But some stratocu banked up along the W
slopes may sneak through and into the Triad today, as we'll stay
within a fast cyclonic mid level flow. Very warm thicknesses of 1370
m at GSO this past evening (around 50 m above normal) are expected
to plunge to 15-30 m below normal by morning, suggesting highs in
the mid 40s to lower 50s, despite plentiful sunshine, with brisk
gusty winds diminishing throughout the day. Radiational cooling
conditions will be decent, although perhaps not textbook as a light
breeze may hold through the night as the surface high builds in
further. Lows 23-32 under clear skies. -GIH


As of 330 AM Monday...

One last weak shortwave trough will cross NC early Tue morning, with
flattening and still-swift mid level flow in its wake, as the split-
flow longwave pattern features a large polar low over SE Canada and
another low near Las Vegas. Low PWs around a quarter inch will
persist through Tue, with a stable column, thus expect plenty of
sunshine as the surface high settles over the Carolinas. This air
mass will likely have undergone some modest modification, so expect
highs to be slightly higher than today but still cool, in the upper
40s to mid 50s. Tue night, the upper level moisture currently seen
upstream over the Four Corners region (including orographic
enhancement of high clouds off the S Sangre de Cristos) will spread
into our area, yielding an incoming veil of high clouds over NC Tue
night. Expect lows of 25-36. -GIH


As of 301 AM Monday...

Dry and cooler conditions are expected for much of the longterm
period. Aloft, wnwly will dominate the period as mid-level ridging
builds upstream across the central US. The ridge will slowly move
east and eventually over central NC by Friday.  At the sfc, cold
high pressure originating in Canada will ooze down into the
southeast through Friday. This feature will promote dry and cooler
conditions Wednesday through Saturday as highs struggle to reach the
lower 50s (Thursday in particular looks quite cool with highs in the
upper 40s).

Latest ensemble guidance has delayed the next chance for rain until
at least Saturday night/Sunday associated with a developing trough
and sfc low over the Gulf of Mexico. The GEFS continues to be a bit
quicker bringing associated precipitation into our area compared to
the CMC and ENS solutions. As such, leaned moreso on the CMC/ENS for
introducing slight to chance POPs early Sunday morning into the
afternoon period.


As of 1230 PM Monday...

TAF period: VFR conditions are expected through the TAF period.
RDU/FAY are likely to waver between SCT/BKN clouds, while RWI should
keep a ceiling through the afternoon. So far all cloud heights have
remained VFR, but an isolated MVFR cloud observation cannot be ruled
out. These clouds should fade after sunset. Wind will be out of the
northwest 10G20kt, with gusts ending at sunset and wind becoming

Outlook: Dry VFR conditions are expected through the outlook period.




NEAR TERM...Green/Hartfield
SHORT TERM...Hartfield
LONG TERM...Luchetti