097
FXUS62 KRAH 221955
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
255 PM EDT Sun Sep 22 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 350 PM Sunday...

Satellite imagery shows the area of low-stratus just to the north-
northeast of the Triangle, where it has persisted since this
morning, albeit slowly eroding with time. A scattered to broken cu
field has developed over the remainder of central NC this afternoon.
The area of stratus has created a significant differential heating
boundary, with temperatures only reaching the low 70s under it and
mid to upper 80s elsewhere. Highs may top out around 90 degrees in
the west and south, while under the stratus and where it lingers
through sunset, highs will struggle to reach the mid 70s. The
surface pressure trough that moved southward through the area today
has settled south of the area as of 3 PM, with the backdoor cold
front draped across the area from the Triad through the Sandhills
and far srn Coastal Plain. Some hi-res guidance still shows the
chance for an isolated shower, mainly over the southern Coastal
Plain/Sandhills ahead of the front this evening, and possibly over
the far northeast Coastal Plain. Otherwise the weather should be dry
through midnight.

Tonight, in the wake of the backdoor cold front, cool surface high
pressure will ridge sswwd into the area. Low clouds/stratus will
develop over the nrn Coastal Plain/ northeast Piedmont around
midnight, spreading quickly and covering all of central NC by Mon
morning. Despite low-level thicknesses some 10m lower in the NE than
last night, with the expansive cloud cover lows may be a couple/few
degrees higher tonight. Lows should range from mid/upper 60s SW to
upper 50s/60 degrees NE. Additionally, some showers could still move
into/clip the northwest Piedmont late tonight/early Mon morn as a
weak mid/upper disturbance riding the sub-topical ridge slides into
the area. There may also be some isentropic lift over the western
Piedmont (which shows up on the 300K sfc off the 12Z NAM) that may
result in some drizzle/light rain around daybreak.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 330 AM Sunday...

Weak H5 rises are expected over the region on Monday as the upper
ridge over the GOM builds towards the Florida Peninsula. The
aforementioned back-door cool front near the SC/NC border early
Monday could retreat back north during they day. Meanwhile,
downstream of the an upper shortwave trough over the Mid/Lower MO
Valley, weak disturbances will continue to eject east atop the mid-
level ridge axis and through the region, keeping a plume of enhanced
mid-level moist and WAA focused over NC and VA, with PWATS forecast
to increase to ~2.0" by Monday evening.

We`ll see considerable multi-layer cloudiness across central NC,
especially the western Piedmont. Weak to moderate destablization
across the southern and western Piedmont will support a chance of
showers and storms, especially during the afternoon and evening,
with general model consensus the potential for scattered
shower/convection to spread east into central and eastern NC Monday
night.

Highs Monday ranging from mid/upper 70s north to mid 80s south. Lows
again in the lower 60s NE to upper 60s south.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 248 PM Sunday...

The frontal boundary from Mon is likely to linger across the western
and southern Piedmont early Tue, before slowly shifting northward on
Wed. Aloft, models are showing an impulse of energy tied to a
shortwave in the OH valley tracking across the region in the SW flow
aloft. Morning stratus across the region is likely to also set up a
differential heating boundary as it slowly erodes over the southern
Piedmont and Sandhills, with highs mid 70s NE to mid 80s SW. While
SPC does not have us outlooked, models are showing MLCAPE between
1000-1500 J/kg with deep-layer shear of 30-35 kts, focused over the
southern Piedmont. This could pose a non-zero severe threat. As a
result, guidance is fairly high on shower/storm chances. Morning
showers are possible in the NE, but aftn/eve convection is favored
to develop first in the west/southern Piedmont and track ENE in the
evening to overnight.

By Wed, the surface boundary is largely favored to lift into VA as a
warm front. A cold front will be weakening to our west in the OH
Valley. Highest storm chances Wed will be over the NW in closer
proximity to the northward moving front and mid-level energy,
focused in the afternoon and evening with diurnal heating. Highs
should trend warmer than average in the upper 70s N to mid 80s S.

Thu to Sun: The overall synoptic pattern and potential impacts from
what develops in the Gulf remains uncertain. While the latest
deterministic GFS, ECMWF, and CMC show decent agreement that the
potential tropical system forecast to develop in the Gulf (80-
percent now from NHC) will get pull northward by troughing over the
mid to lower MS valley sometime late Thu or Fri over the SE US,
their respective ensembles still show a large spread in possible
scenarios. As a result, confidence on expected impacts from heavy
rainfall or gusty winds late this week to weekend, remain low. Where
the tropical system tracks ultimately will depend on the location of
the trough in the midsection of the country, as well as the ridge
off the SE coast, and whether any blocking sets up over the Great
Lakes or northern Great Plains. The inland landfall could be as far
west as the coast of AL or as far east as NE florida, per the ECENS
00z low tracks. For now, we have highest PoPs late Thu into Sat of
30-40 percent, decreasing to 20 percent by late in the weekend Sun.
This is likely to change, however, as models come into better
agreement in the coming days. Consequently, temperatures are also
uncertain, but for now are favored to be near or slightly below
average in the mid/upper 70s to around 80 Fri-Sun.


&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
As of 200 PM Sunday...

24 hour TAF period: An area of MVFR cigs lingers roughly from KRDU
to KRWI and north, with few/scattered cu at 15-25 kft developing
across the rest of central NC. Skies may bounce between sct and bkn
MVFR for the next several hours, most likely at KRDU and KRWI, but
possible also at KFAY and maybe even the Triad briefly. Otherwise,
VFR conditions should prevail through sunset, with winds generally
nely to ely. Some hi-res guidance still suggests some isolated
showers could develop this aft, but should largely miss the
terminals, coming closest to KRWI and KFAY.

Widespread IFR/LIFR stratus will spread across central NC, mainly
around and after midnight, with a period of MVFR/IFR vsbys expected
Mon morning. Skies will be slow to scatter/lift on Mon, with only
KRWI and possibly KFAY improving to VFR before the end of the TAF
period and MVFR/IFR everywhere else through 18Z.

Outlook: Mainly VFR conditions expected each day, with the exception
of sub-VFR fog/stratus each morning. There is a chance for mainly
afternoon/evening showers/tstms each day, which could result in
periods of sub-VFR conditions where/when they occur.

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...KC
SHORT TERM...CBL
LONG TERM...Kren
AVIATION...KC