-- Discussion containing changed information from previous version are highlighted. --
339
FXUS62 KRAH 230736
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
335 AM EDT Mon Sep 23 2024

.SYNOPSIS...
A back-door cold front will move through central NC through this
evening, then stall and waver over SC and southwestern NC Monday
through Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 945 PM Sunday...

Behind the passage of an initial cold front and north to northeast
wind shift, a continued moist but cooler airmass has been deposited
over much of central NC. A secondary and drier cold front is seen in
regional observations and satellite imagery spilling southwest over
southeast VA and northeast NC. In between these two fronts over
central NC, the cooler and still moist airmass will promote the
development of a widespread blanket of stratus over most of the
area. Slowest to cloud over looks to be the southern Piedmont which
may be the favored area of some initial fog < 1 mile to develop.

Some moisture pooling in the upslope region, and gradual moist
isentropic ascent over the northwest Piedmont may allow for some
light drizzle to develop early Mon morning, but flow through the
saturated layer will be weak so confidence this will result in any
measurable precipitation is low given inconsistencies within high-
res guidance. Lows will gradually drop into the mid/upper 60s (W) to
low 60s (NE).

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 415 PM Sunday...

A ridge accompanying a sub-tropical, 500 mb anticyclone along the
Gulf coast will progress across the Southeast through 12Z Tue, with
associated anticyclonic flow across cntl NC. Meanwhile, convectively-
perturbed, wswly to swly flow will be directed from the lwr MS
Valley to the OH Valley and cntl Appalachians, downstream of a
synoptic shortwave trough that will deamplify across the cntl Plains
and mid MS Valley.

At the surface, the backdoor cold front now progressing through cntl
NC will stall over w-cntl SC early Mon, then retreat nwd into the
srn NC Piedmont Mon afternoon-night. High pressure centered over
Atlantic Canada will otherwise extend swwd across the Northeast and
middle Atlantic, including ern and e-cntl NC.

Widespread low overcast will likely have developed over most of cntl
NC by daybreak Mon. This post-frontal, low overcast may be
accompanied by patchy light rain and drizzle over the nw Piedmont
through the morning, in the upslope regime there where point
forecast soundings depict saturation in the lowest 1000-2000 ft. The
early day clouds will lift and at least partially clear, especially
away from the nw Piedmont, with afternoon warming into the mid/upr
70s north to lwr 80s south. Low-level moisture pooling along and on
the immediate cool side of the surface front will favor weak to
moderate diurnal destabilization, strongest across the srn Piedmont
and Sandhills. There remains a signal in model guidance for an area
of showers and storms to move into the srn and wrn NC Piedmont
during the late afternoon-evening, with a risk of a strong storm or
two over the srn Piedmont, where both instability and
unidirectional, wnwly flow are forecast to maximize. A chance of
showers, and generally weaker storms, should then spread ewd through
the night, as PWs increase to between 1.75-2" and support continued
weak instability. Widespread low overcast should otherwise redevelop
in an unseasonably moist/humid regime, with low temperatures in the
60s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
As of 335 AM Monday...

Increased chance of precipitation through the long term period
despite the uncertainty with respect to the development and track of
the tropical cyclone in the Gulf of Mexico mid week.

On Wednesday, a cold front moving east across the OH and TN valley
will weaken as it moves into the region Wednesday afternoon. Expect
scattered showers and isolated storms in the afternoon especially in
the NW Piedmont as models are depicting afternoon CAPE values range
from 500-1000 J/kg. With that, high temperatures in the NW will
range from the upper 70s to low 80s and in the SE low to mid 80s.

For the rest of the week and into the weekend, deterministic models
are showing a tropical cyclone landfall somewhere along the Florida
Panhandle or Big Bend area of Florida Thursday afternoon or evening.
While the intensity, timing, and location is uncertain for now,
models have come in more agreement in the past few model runs.
Either way, Central NC is expected to begin to see some impacts as
early as late Thursday night/early Friday morning. While most models
show the center of the storm staying west of the region, increased
moisture from the Atlantic will help  support showers and storms
through the day Friday. For the weekend, the forecast will depend
largely on the the timing and location of the TC remnants, thus kept
low end slight chance PoPs for Saturday and Sunday but with very low
confidence.

Temperatures will be a few degrees above normal on Thursday with
highs in the upper 70s to low 80s. The rest of the week/weekend
becoming near average for the the rest of the week and weekend with
highs ranging mid/upper 70s to low 80s.
-- End Changed Discussion --

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
As of 140 AM Monday...

NELY low-level flow behind back the back-door cold front passage has
ushered in IFR to MVFR ceilings into the area. Ceilings should lower
further to LIFR through 12z, especially at KINT and KGSO, where the
low-level saturated layer will bank up against the eastern slopes.
Additional, patchy fog may promote reduce visibilities around
daybreak, with models currently showing the best fog signal over the
northern coastal plain, INVOF KRWI.

At KINT, KGSO, and KRDU:  The sub-VFR ceilings will be slow to lift
throughout the day, eventually lifting to MVFR during the afternoon.
Ceilings could temporary improve to VFR during the late
afternoon/early evening, but should be short-lived before ceilings
lower again during the evening and overnight hours

At KRWI and KFAY: Drier air across eastern NC should allow flight
conditions to improve much quicker, Ceilings at KRWI are expected to
lift to VFR by mid/late morning, while KFAY could be delayed
until the afternoon.

Precipitation wise: Scattered rain showers and storms are expected
to spread west to east across the area during the evening and
overnight hours, with the best rain chances expected at KINT and
KGSO.

Outlook: Expect daily scattered showers and storms through much of
the work week. A tropical system could bring impacts to our area by
Friday, but confidence is currently low. Additionally, sub-VFR
restrictions in fog/stratus will be possible each morning.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...Swiggett
SHORT TERM...MWS
LONG TERM...CA
AVIATION...CBL