-- Discussion containing changed information from previous version are highlighted. --
767
FXUS62 KRAH 201836
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
235 PM EDT Fri Sep 20 2024

.SYNOPSIS...
An upper level trough along the East Coast will shift slowly
eastward and offshore through Saturday morning, as a weak surface
high pressure ridge extends from New England down through the
central Carolinas. An upper level disturbance will track southeast
through the Mid Atlantic region late Saturday through Saturday
night. An upper level high pressure ridge will then build in from
Texas across the Gulf and Southeast states through early next week.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 1020 AM Friday...

No major changes with this morning update. There is still a bit of
lingering fog in the southwest Piedmont as of 930 AM, but that is
expected to dissipate in the next hour or so as the boundary layer
continues to mix out. The 12Z upper air analyses show the upper
trough situated along the East Coast, with the anticyclone over srn
TX, ridging newd through the central Plains and mid MS Valley. The
atmosphere remains saturated over central NC at H7 an H85. At the
surface, high pressure encompasses the mid-Atlantic and Carolinas,
while a low sits off the northern mid-Atlantic coast.

A mid/upper level s/w is swinging through central NC this morning
and should exit to the east this afternoon. Some drier H7 air is
expected to advect into the area from the northeast, ahead of a
trailing mid-level disturbance sliding sewd through the northern
Coastal Plain and northeast Piedmont late this aft/eve. It is this
feature that could help some showers develop. Exactly where the
mainly isolated to scattered showers will develop remains somewhat
uncertain, but for now the best chances will likely be along the H7
moisture gradient (over the NC Piedmont) as the mid-level
disturbance swings through the area. Some of the hi-res guidance
still shows about 500 J/Kg of SBCAPE across central NC this aft/eve,
so cannot rule out an isolated thunderstorm. Highs ranging from
around 80 degrees north to mid 80s south. -KC

From the previous discussion (as of 235 AM Friday): Any showers
should peter out and shift to our S early this evening, leaving dry
conditions overnight, however another round of patchy fog and low
stratus is probable late tonight, following persistence with little
change in antecedent conditions and surface wind. Lows generally 60
to 65. -GIH

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 315 AM Friday...

Confidence is increasing in scattered showers and perhaps a few
storms across the N and W Piedmont and far NE late Sat. A prominent
shortwave seen on WV imagery over the Upper Midwest is on track to
round the top of the amplified ridge centered over TX and covering
much of the central CONUS through tonight, before diving SE through
the Mid Atlantic region late Sat and Sat night. While the timing of
this DPVA may not take full advantage of the daytime heating and
resulting destabilization this far SE, we should see an uptick in
mid level flow to support some deeper convection esp over the
mountains to our NW, and this activity may spill SE into our NW and
far N sections very late in the day and through the evening. Most
deterministic models and ensemble systems support this, with
isolated to scattered coverage across our NW and far N late
afternoon through the evening, and this is where we`ll have 15%-30%
pops, mainly from 21z-06z but with perhaps an isolated shower or two
lingering in the far NE overnight. With dry weather through much of
the Sat daytime hours, temps should reach slightly above normal
highs around 80 to the mid 80s, as thicknesses are projected to be 5-
10 m above normal. Lows in the low-mid 60s Sat night. -GIH

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
As of 235 PM Friday...

Near to slightly above normal temperatures will start the period
early next week. Forecast confidence decreases after Wed with
ensemble solutions not in agreement on the pattern. As such,
temperatures are less certain but currently projected to be near to
slightly below normal in the upper 70s to low 80s. While rain
chances are possible Mon through Fri, highest confidence for showers
exist Tue into early Thu.

Ridging builds in from the TN valley Mon, while at the surface the
passage of a backdoor front will settle somewhere along the far
southern Piedmont and along the SC border. High pressure will nose
down into the region from Maine. Highs will be lower from the weak
cold advection and some daytime stratus. Expecting mid/upper 70s NE
to low 80s SW. We cannot rule out an isolated shower/storm in our
far southern and southwest zones along the stalled boundary, as well
as along the far NW Piedmont tied to some weak upslope.

Come Tue and Wed, guidance shows a system across the MS valley
trying to bring a cold front into the region. Ensemble solutions
start to diverge, however, regarding the frontal passage, if at all,
depending on the strength of the ridge in the far NE Gulf and the
trough over the Great Lakes. Solutions that bring the front through
show a passage late Wed night to early Thu. Have retained 20-40
percent chances of isolated to scattered storms, highest presently
for Wed, but confidence remains on the low end.

By mid to late week, ensemble solutions continue to diverge and
overall forecast confidence is low. Some ensemble solutions bring NW
flow aloft with a cold frontal passage, favoring drier conditions
and slightly below normal temperatures, while other solutions keep a
trough to our west in the MS valley, favoring warmer highs. This
pattern would favor higher storm chances in the late-week period as
it could pull deeper moisture into the area from the Gulf. NHC is
tracking the potential development of a tropical depression (50
percent chance of formation) over the northwestern Caribbean Sea and
southern GOM late next week. If something were to indeed form, its
energy could get pulled into the Deep South by the aforementioned
trough, depending on the pattern. Given the large model spread, PoPs
Thu/Fri are only 20-30 percent.
-- End Changed Discussion --

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 155 PM Friday...

24 hour TAF period: Aside from a few isolated pockets of MVFR cigs
(KGSO), VFR conditions should prevail through at least midnight.
Isolated to widely scattered showers have already developed over the
NC Piedmont and will largely linger through the afternoon/early eve.
While an isolated thunderstorm cannot be ruled out (highest chance
would be at KGSO/KRDU), chances are too low to include at this time.
Shower activity should abate after sunset, with dry weather expected
thereafter. Winds should largely be nely around 5 kts, going calm
overnight. Biggest aviation concern is the chance for early morning
fog and low stratus at all terminals, mainly between 08Z and 13Z
Sat. Conditions should improve quickly Sat morning, with VFR
conditions returning by mid/late morning.

Outlook: VFR conditions should generally prevail through mid-week,
with the exception of sub-VFR fog/stratus each morning. Light rain
or showers will be possible each day but those details remain fairly
uncertain at this time.

&&

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

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...KC/Hartfield
SHORT TERM...Hartfield
LONG TERM...Kren
AVIATION...KC