367
FXUS62 KRAH 220734
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
335 AM EDT Sun Sep 22 2024

.SYNOPSIS...
A back-door cool front will drop south into the area this afternoon
and evening and tonight. The front is expected to become quasi-
stationary INVOF of upstate SC and southern NC, eventually washing
out early week as weak high pressure extends south down the mid-
Atlantic coast.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 330 AM Sunday...

Central NC will remain in the NW flow between the upper ridge
centered over the western GOM and lower MS Valley and upper trough
moving east out into the western Atlantic. A back-door cool front is
forecast to work it`s way south through the area during afternoon
and evening.

Upper impulse and associated convective cluster will exit SE of the
area over the next few hours. In it`s wake, some patchy fog and low
clouds/stratus may develop around or shortly after daybreak,
especially across the northern/central coastal plain and possibly
extending into the eastern Piedmont counties as a back-door cool
front sags in from the NE.  These low clouds could linger/hold on
over NE portions for a fairly substantial portion of the diurnal
heating cycle, which will likely set-up an impressive NE to SW
temperature gradient across the area, while also making for a
challenging max Temp forecast today, especially along it`s eventual
western fringes. HREF probabilistic guidance indicates as much as 8
degree spread in afternoon temps, with the greatest uncertainty
centered over the central Piedmont, including the Triangle. Highs
ranging from mid/upper 70s northern coastal plain, lower/mid 80s
interior sections, and upper 80s/near 90 across the southern
Piedmont.

Isolated showers/storms will be possible as the front slips
southeast, mainly across eastern/coastal plain sections where the
best instability is forecast. Widespread low clouds/stratus will
spread NE to SW during the the evening and overnight hours.
Additionally, some showers could spread into the western/NW Piedmont
tonight as shortwave impulses spread in from the west within a mid-
level plume of enhanced moisture and WAA. Lows ranging from lower
60s NE to upper 60s southwest.

&&

.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 /MONDAY THROUGH SATURDAY/...
As of 230 PM Saturday...

* Near to slightly above normal temperatures into midweek, followed
  by seasonal to slightly below average late week and weekend

* Shower and storm chances highest Tue into Thu

* Forecast confidence decreases mid to late week as ensemble systems
  continue to differ on the overall synoptic pattern and possible
  tropical influences

We will start the week with ridging building into the area at mid-
levels from the north and northeastern Gulf. High pressure will
build into the area from the Eastern Seaboard and Canada. Models
still show a lingering backdoor front to our southwest in northern
SC, though it appears models have trended further south with its
location. As such, rain/storm chances are lessened Mon aftn/eve, but
still cannot rule out a 20-30 percent chance over the western and
southern Piedmont. Temperatures will be near normal in upper 70s to
low 80s.

Ridging will continue into midweek, though we should get increasing
influence from a trough over the MS/OH valleys and Great Lakes late
Tue through early Thu. Model and ensemble solutions start to diverge
on how the trough evolves as it moves east, but there does appear to
be a general consensus that a cold front will try to move through
sometime Thu morning. It`s still unclear whether it will actually
move through or stall out and linger NW of us. Ahead of that front,
shower and storm chances should increase (30-60 percent), primarily
in the late Tue through Wed night period. Temperatures should rise
above normal ahead of the front to above average in the low to mid
80s.

Probabilistic and ensemble solutions continue to vary widely in the
Thu to Sat timeframe with respect to the synoptic pattern. Some
ensemble cluster solutions indicate troughing over the MS valley and
ridging off the western Atlantic (aka latest GFS/CMC), which would
favor warmer highs and help draw northward any disturbance in the
Gulf later in the week. Where it tracks though is widely varied.
Other solutions show troughing nearby with the aforementioned cold
front, keeping rain chances elevated. And still a third solution
shows a rex/omega ridge pattern near the OH valley and troughing on
either side, which could favor drier conditions to start but also
advect any tropical system in the Gulf over the weekend. This is
seen in the prior 00z ECMWF. Speaking of the Gulf, NHC now has a 60-
percent chance of tropical development late next week over the south-
central Gulf. Where the system would move is highly dependent on the
pattern discussed above, which is too uncertain, but certainly bears
watching, given a wide range of potential impacts. As a result, have
kept rain chances low Thu to Sat, with temperatures near to slightly
below normal in the upper 70s to near 80.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
As of 138 AM Sunday...

A cluster of showers and storms and associated sub-VFR restrictions
will impact KRDU and KRWI through 08z, and KFAY through ~10z. In the
wake of the convection/rain, some patchy fog and MVFR ceilings may
develop around or shortly after daybreak, mainly at KRWI. These
sub-VFR ceilings could linger at KRWI into the early afternoon
before lifting. Elsewhere, flight conditions should remain
VFR.

Then during the afternoon and evening, a back-door cold
front, denoted by a NELY wind shift, will push southeast through the
through the area, bringing widespread LIFR to IFR restrictions
in stratus and fog Sunday evening/night.

After 06Z Monday: 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 also
briefly reduce flt conditions at times.

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...Kren
AVIATION...CBL/np