402
FXUS62 KRAH 260012
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
810 PM EDT Wed Sep 25 2024

.SYNOPSIS...
Tropical Cyclone Helene is forecast to make landfall in the
Florida Big Bend late Thursday, then move north and northwest across
Georgia and into the Tennessee Valley while weakening through
Friday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 315 PM Wednesday...

Despite 1500-2500 J/kg of SBCAPE and positive H8 moisture flux, the
presence of mid level dry air (noted on WV imagery) over all but the
far NW and near-normal PWs have led to scant convective coverage so
far, limited to a cluster of scattered showers over our S areas so
far. Most CAM output including the HREF probability matched mean
depict little more than isolated to widely scattered showers and a
few storms over the area through early evening, becoming even more
sparse late evening into the overnight, and this scenario will be
reflected in pops through tonight, with chances topping out near
climatology and the higher-end pops restricted to the far NW. The
highest rain chances will remain to our W, close to the upper
divergence maximum swath on the E edge of a 100+ kt southerly upper
jet extending through central and eastern TN, where PWs will be
slightly higher through tonight. Another round of low stratus is
expected late tonight, once again with highest confidence and lowest
cigs over the NW half. Lows in the upper 60s to lower 70s. -GIH

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 235 PM Wednesday...

On Thursday morning, Hurricane Helene should be intensifying over
the Gulf of Mexico as it moves north, likely to make landfall along
the Florida Gulf Coast Thursday evening. Scattered showers and
isolated thunderstorms will continue Thursday morning along the
leftover boundary from today, slowly expanding to the east Thursday
afternoon. Have maintained likely pops across western counties
Thursday afternoon. As Helene weakens to a tropical storm by the
time it reaches northern Georgia Friday morning, rainfall will
expand farther across the forecast area Thursday night, with the
greatest coverage and intensity of rainfall likely to occur Thursday
night and Friday morning. 12Z models indicate that rain could come
to an end a little quicker than previously forecast as the dry slot
moves in from the south - likely pops will continue north of US-64
Friday afternoon, but pops should become more scattered across the
south in the afternoon, and all locations should be dry by late
Friday night.

While there is still spread as to the exact time of Helene once it
makes landfall, the overall trend across central North Carolina has
been a reduction in rainfall totals. A general one to two inches of
rainfall is expected, with greater amounts to the west. The maximum
wind gusts remain generally unchanged, ranging from 20-25 mph across
the east to 30-35 mph in the west. There have been some locations
that have received as much as five inches of rain in the last three
days. Considering how wet the ground is in some locations, despite
wind gusts that are expected to remain below tropical storm status,
there is the potential for many more trees to come down than would
be expected for the given wind speeds. The preceding rainfall will
also increase the risk for flash flooding and river flooding,
although there is not enough confidence in higher rainfall rates to
issue a flood watch. There will also be a risk for tornadoes on
Friday with ample moisture and instability for thunderstorms. This
threat will be evaluated more closely tonight and Thursday once
additional high-resolution model guidance is available.

High temperatures will range from the mid 70s in the northwest to
the mid 80s in the southeast. Low temperatures will range from the
upper 60s to the mid 70s Thursday night, then be in the mid to upper
60s Friday night as clouds clear out Friday night.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 244 PM Wednesday...

The mid-upper low/trough expected to pull Hurricane Helene northward
will linger over the TN Valley Saturday before slowly oozing
northeast through the Mid-Atlantic through early next week.

Saturday: The remnants of Helene will likely have moved over TN by
Saturday morning. The anomalous moisture associated with this system
will have congealed well to the north and west of central NC,
promoting a primarily dry day on Saturday. By Saturday evening,
however, some models suggest some of that anomalous moisture may
trickle back into our northwest Piedmont. As such, maintained a low-
end slight chance for showers Saturday afternoon and evening.
Otherwise, daytime highs in the lower to mid 80s is expected.

Sunday through Wednesday: As the mid-upper low slowly migrates
across the mid-Atlantic through early next week, additional daily
showers and thunderstorms will be possible.  Will maintain low
slight to chance PoPs each day for now, with highest chances across
the north where better moisture will pool and upper forcing for
ascent appears strongest.  There does seem to be good consensus that
the upper trough will shift offshore through Wednesday, behind which
nwly flow aloft will usher in drier air by mid-week (mean ensembles
suggest <1 inch PWAT may encompass our area by Thursday morning).

Temperature wise, we`ll generally see upper 70s to lower 80s through
Wednesday.  There is a signal for a potential cool down Wednesday
night into Thursday, but confidence is low at this point.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 810 PM Wednesday...

Generally VFR conditions are expected to become IFR to LIFR
overnight into Thursday, especially from RDU and GSO to INT.
Isolated showers will be possible tonight, with scattered showers at
GSO and INT. Showers with occasional IFR to MVFR conditions are
expected at INT and GSO Thursday, with generally MVFR to VFR cigs at
RDU, FAY, and RWI. Scattered showers and thunderstorms are expected.

Looking beyond 00z Fri, what is now Hurricane Helene is expected
to make landfall in the central FL panhandle early Thu evening, then
track N and NNW through GA and into eastern and central TN Thu
night through early Fri afternoon. Moist flow ahead of and east of
Helene will bring predominantly adverse aviation conditions to much
of central NC Thu afternoon through early Fri morning, with periodic
rain bands bringing occasionally sub-VFR conditions in moderate to
heavy rain with isolated storms, along with frequent gusts over 20
kt. Low level wind shear may occur esp at FAY/INT/GSO early Fri
morning, but confidence is low. Conditions will improve to VFR from
S to N Fri, lasting through Sat. A chance of showers/storms will
return esp to the NW Sun into Mon. -GIH

&&

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

&&

$$
SYNOPSIS...Badgett
NEAR TERM...Hartfield
SHORT TERM...Green
LONG TERM...Luchetti
AVIATION...Badgett/Hartfield