498
FXUS62 KRAH 010910
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
410 AM EST Mon Dec 1 2025

.SYNOPSIS...
A cold front will move across central and eastern NC, then offshore,
this morning. Cold high pressure will migrate quickly across and
offshore the Middle Atlantic today and tonight, ahead of low
pressure that will develop and rapidly strengthen from the Southeast
to the Middle Atlantic coast on Tuesday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 245 AM Monday...

* Dry through the day, with rain chances returning late tonight.

* Below normal high temperatures, with near normal lows.

A cold front will continue to push through central NC overnight,
exiting the region by daybreak this morning. This will allow for
high pressure to pass north of the region through the Great Lakes
region and into the northeast US, setting up another wedge airmass
by afternoon/evening. At the same time, a trough and associated cold
front will start to approach from the west late tonight as a low
pressure system starts to form and moves up the southeast coast.
This will allow for a soaking rain to start spreading into the
region from the west shortly after midnight. The HREF 6 hour local
probability matched mean shows generally 0.15 to 0.75 inches of rain
between 1 and 7am for central NC, with the greater values to the
west. Widespread rain will continue into Tuesday.

High temperatures should be about 10 to 15 degrees below normal this
afternoon. This will equate to highs in the mid 40s north to around
to slightly above 50 in the south. Overnight lows will dip to near
freezing in the north to low 40s in the south. Temperatures look to
be above freezing when and where rain will fall late tonight.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 340 AM Monday...

* A cold, soaking rain early Tue will yield to west to east drying
  and clearing during the afternoon and especially Tue night

A shortwave trough comprised of a couple of perturbations now
stretching across the Four Corners and Southwest will have reached
the OH to lwr MS Valleys by 12Z Tue and lift across and offshore the
Middle Atlantic and Carolinas late Tue-Tue night. A strong low
through mid-level WAA regime, and plume of anomalous moisture
characterized by PWs around 200% of normal, will precede the trough
and be swept across and offshore the Carolinas through early Tue
afternoon.

At the surface, the center of a 1035 mb, Arctic high now centered
over IA will migrate quickly ewd and reach Nova Scotia by 12Z Tue,
while steadily weakening to near 1025 mb. A narrow, in-situ cold
damming ridge will extend swwd from the transitory and weakening
high and across the favored cold air damming region across the
Carolinas and neighboring VA and GA on Tue, while coastal low
pressure will rapidly deepen from around 1010 mb along the coast of
the Carolinas Tue morning to around 980 mb off the Nova Scotia coast
Wed morning. Through the same time, a weaker high than the first,
centered around 1025 mb over the srn Plains Tue morning, will
migrate ewd and into the OH and TN Valleys, with associated cold and
dry air advection that will spread east of the Appalachians and
across cntl NC Tue afternoon and night.

The transitory and weakening nature of the Arctic high is not
favorable for wintry precipitation in cntl NC, where forecast
partial thickness and surface wet bulb freezing values, and the top-
down approach from point soundings, all indeed suggest just a cold
rain. Storm total rainfall amounts are expected to range from around
0.75" over the nw Piedmont to around 1.5" in the Coastal Plain, the
latter where where low-level Fgen and weak elevated instability
nearest the deepening cyclone will probably yield a swath of highest
totals.

It will be a cold and raw morning amid widespread rain and peak cold
air damming, when temperatures will be in the mid/upr 30s over the
nw Piedmont to lwr 40s in the Coastal Plain. However, the departure
of the rain shield, and downslope flow and CAA in the stable CAD
layer, will likely yield east to west erosion of the CAD airmass
behind the coastal low (a CAD erosion scenario) during the afternoon
and evening, when temperatures will moderate through the 40s, to
perhaps lwr 50s over the srn/wrn Piedmont. A clear and colder Tue
night will follow, with temperatures mostly in the 20s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 400 AM Monday...

Downstream of a positive tilt trough that will extend from Four
Corners and Southwest, swwd through a cyclone over the sern N.
Pacific, fast/quasi-zobnal flow will prevail across the Southeast
and Carolinas. To what degree and how quickly shortwave energy from
that positive tilt trough ejects ewd will have ramifications on
downstream vertical motion and contribution to cyclogenesis near the
coast of the Carolinas Fri-Sat. While forecast confidence is below
average in that regard, the trend in model guidance has been toward
generally more suppressed and drier solutions, driven mostly by a
plume of mid-level WAA and Fgen, and such that precipitation
centered around Fri-Fri night will very likely be much lighter than
this Tuesday`s system.

At the surface, high pressure will weaken while migrating across and
offshore the Southeast Wed-Thu, ahead of a dry cold front that will
lead an Arctic high across the Middle Atlantic and into the
Carolinas Thu night-early Fri, then quickly offshore by Fri night. A
wavy frontal zone draped from the nrn Gulf to just offshore the
Southeast coast may allow for at least a couple of episodes of, as
it appears at this time, weak cyclogenesis Fri-Sat.

The fast and progressive nature of the pattern described above will
favor a continuation of transitory and weakening Arctic highs as
they migrate across the Great Lakes and Middle Atlantic, then
offshore, which is not favorable for more than nuisance wintry
precipitation mostly at onset in cntl NC. Indeed, the aforementioned
mid-level WAA regime would support adequate lift when partial
thicknesses are initially supportive of snow if the precipitation
were to arrive early in the day Fri, but with subsequent warming
that would favor a relatively quick transition to rain. While there
could also be an intervening, short period of light freezing rain
over the nw Piedmont before surface temperatures rise above
freezing, that too would be short-lived, self-limiting in the
absence of a more favorably located and anchored surface high, and
low impact.

Forecast confidence is even lower for Sun, but with a general signal
for drier and less chilly conditions behind whatever transpires
from the mostly light precipitation Fri-Sat.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
As of 110 AM Monday...

The 06Z observations are showing that much of the region`s ceilings
have returned to VFR as the light rain continues to move eastward
out of central NC. The trailing cold front is also on the doorstep
of the NW Piedmont. Once the front moves through, VFR conditions
should prevail everywhere for much of the 24 hour TAF period. Ahead
of the front and the associated dry air, a few areas may see some
patchy fog develop over the next few hours. A few locations in the
southeast are showing lowered visibilities, but confidence is too
low to include at any TAF sites. Additionally, occasional gusts will
be possible overnight and through the morning with the frontal
passage. The best chance for more frequent and stronger gusts looks
to be in the east, where the wedge airmass did not reach or is not
as deep. Winds overnight and through the day should veer from
northwesterly to easterly. The next round of sub-VFR ceilings look
to hold off until around 06Z Tuesday.

Outlook: Another storm system will bring widespread rain and IFR or
lower conditions late Mon night through Tue. VFR returns Wed and Thu
under high pressure. Another late-week system may bring rain/showers
late Fri-Sat.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...MWS
NEAR TERM...LH
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...LH/AK