398
FXUS64 KHUN 251714
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1214 PM CDT Wed Sep 25 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 1009 AM CDT Wed Sep 25 2024

Todays weather will continue to be influenced by a stalled cold
front draped over the area. Current observations indicate the
front is currently located in NW AL. Model guidance indicates the
front will linger in NW AL for most of the day and then slowly
push SE this evening. The frontal boundary will continue to
provide lift to support showers and thunderstorms along and to the
SE of the front through most of the day. Fortunately, the
overcast conditions will greatly limit instability keeping storms
sub severe.

As for rain, overnight totals were scattered with totals ranging
from a trace in NW and NE AL to near an inch along the I-65
corridor. HREF guidance indicates near an inch of additional
rainfall possible along and east of I-65 through the remainder of
the day today. This is significantly less than previously forecast
and will hopefully keep soils in NE AL from becoming fully
saturated prior to Helene. As the front pushes east late this
evening, rain chances will begin to decrease through the overnight
hours yielding a brief period of low rain chances this evening
through tonight before tropical impacts arrive, see short term for
more details.

&&

.SHORT TERM...
(Tonight through Friday night)
Issued at 233 AM CDT Wed Sep 25 2024

The front will drift more to the east closer to the I-65 corridor
tonight, with rainfall diminishing with the loss of weak buoyant
energy. Weak convergence along the front may still allow for some
shower/tstms overnight, mainly east of I-65. The influx of cooler
air will at least translate into lows tonight in the lower/mid
60s. The pattern will then change considerably starting Thu, as
Tropical Storm Helene in the western Caribbean lifts northward and
strengthens into a hurricane. Outer rain bands/squalls associated
with Helene will begin to spread northward into the eastern half
of the region. Periods of moderate/heavy rainfall can be expected
into Thu night, as the hurricane makes landfall along the FL Big
Bend region and then lifts to the NNE. Additional rainfall amounts
around 2-4 inches are possible Thu/Thu night, especially east of
I-65 and a Flood Watch will likely be needed for the eastern half
of the area during this time frame. Wind gusts east of I-65 could
also be around 20-30 MPH into Thu night. These speeds are just
below Wind Advisory criteria, although any change in the track of
Helene to the west once inland could result in higher winds/gusts.

The threat for localized/flash flooding could extend into Fri
morning for areas east of I-65, as the remnants of Helene begin to
lift N/E of the area and the upper low to the west drifts into the
lower MS Valley. Going more into the day Fri, the better moisture
convergence axis between these two systems will lift northward
into TN, allowing for a diminishing trend in the rainfall over
much of the area. This pattern continues into Fri night, as the
remnants of Helene begin to be absorbed into the upper low to the
west. Given the continued cloud cover/rainfall, highs Thu/Fri will
likely trend in the lower/mid 70s, with lows into early Sat predom
in the mid 60s/near 60F.

&&

.LONG TERM...
(Saturday trough Tuesday)
Issued at 233 AM CDT Wed Sep 25 2024

The upper low will then begin to lift N/E of the central TN Valley
this weekend, providing for a low chance of showers (20-30%) both
Sat/Sun with some decreasing cloud cover. Minimal rain chances are
expected into the first half of the work week as well, as a
reinforcing cold front out of the NW sweeps thru the region. With
the decrease in cloud cover/rainfall, highs this weekend will be
more in the mid/upper 70s, before climbing into the upper 70s/near
80F Mon/Tue. Overnight lows thru the latter half of the forecast
period also look to remain in the mid 60s/near 60F.

&&

.AVIATION...
(18Z TAFS)
Issued at 1210 PM CDT Wed Sep 25 2024

Rain bands in assoc/w a front moving across the are mainly
impacting the KHSV terminal and areas to the east. RA/SHRA may be
close to KMSL and possibly impact the site through 12Z, but
confidence is too low to warrant a mention in the TAF. Otherwise,
impacts to vis/cigs will be minimal at either site with mainly lgt
SHRA expected as the main belt of instability and TSRA will be
confined to our east. Increased SHRA in assoc with the combined
effects of the stalled front and Helene will begin to impact areas
mainly to the east of the TAF sites after 12Z. SHRA will begin to
increase mainly after the end of the TAF period (18Z) at KHSV,
but impacts will be gradually lowering cigs into MVFR range late
in the period, with potential for MVFR vis if any brief mdt SHRA
impacts either site.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch through Friday afternoon for ALZ008>010.

TN...Flood Watch through Friday afternoon for TNZ097.

&&

$$

NEAR TERM...RAD
SHORT TERM....09
LONG TERM....09
AVIATION...KDW