444
FXUS64 KHUN 241933
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
233 PM CDT Tue Sep 24 2024

...New NEAR TERM, SHORT TERM...

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 233 PM CDT Tue Sep 24 2024

The remainder of the day will see increasing rain and storm
chances as a cold front creeps in from the west. SPC mesoanalysis
indicates 2500-3000 J/KG of CAPE present in NW AL, with totals
decreasing to the east. This, coupled with 40-45 KTS of bulk
shear will certainly be sufficient enough to support more
organized storms and maintain our severe threat this afternoon.
Current idea is that scattered showers and storms will develop
across the area from 1-3 PM and begin to combine into multicell
clusters. Main threats will be damaging winds and frequent
lightning.

The severe threat looks to greatly diminish after sunset with the
loss of daytime heating. The cold front looks to slowly continue
to push east and will likely bisect a portion of our area for much
of the night. The lingering boundary will support continued
rain through the night along and east of the front, which will
likely be roughly east of I-65. Enough CAPE may linger to support
some thunder overnight but the concern will quickly transition to
heavy rainfall and localized flooding. The flooding concern is
driven by the high possibility for training storms overnight.
While cold front driven rain will come to an end tomorrow, a bulk
of the rainfall will likely fall tonight with 1-3 inches possible
with highest totals in the east. If on the roads tonight or early
tomorrow morning make sure to watch out for localized flooding
and ponding of water.

&&

.SHORT TERM...
(Wednesday through Friday)
Issued at 233 PM CDT Tue Sep 24 2024

Rain is likely to start the day on Wednesday with continual
support from the frontal boundary. The front looks to stall over
our area as it begins to interact with Tropical Storm Helene.
A medium chance of showers and thunderstorms, scattered in
nature, are likely through most of the day tomorrow, however the
severe threat will be significantly less than today. Rain chances
will decrease through the evening however with Tropical Storm
Helene continuing to move NE, a brief period of low rain chances
will be our only relief between monitoring the cold front and the
transition to monitoring the tropics.

Tropical Storm Helene is forecast to make landfall as a major
hurricane on Thursday evening. While the center and worst of the
storm itself is forecast to move east of us, Helene is forecast to
be very large, thus its impacts will be felt well beyond the
center of the storm. For the TN Valley, we will begin to
transition into Helene`s influence Thursday during the day. Rain
chances and wind speeds will gradually pick up as Helene pushes
north. Current forecast has wind gusts 20-30 MPH from Thursday
during the day through Friday evening. NE AL overnight on Thursday
will see the highest gusts. While current forecast does not
warrant a Wind Advisory, it would still be a good idea to bring
in loose objects.

Rainfall will be our main concern as Helene moves through. Current
forecast supports widespread rain totals of 2-5 inches of rain
from Wednesday night through Saturday morning. While this amount
alone is likely manageable, we have two concerns regarding the
rainfall forecast. The first is that this rain is in addition to
the 2-4 inches of rain we are expecting with the cold front from
Tuesday (today) into Wednesday. It is very likely that soils will
be very saturated by the time tropical rain from Helene gets here
and make NE AL much more prone to flooding than it otherwise would
be. The second concern related to how Helene will interact with
the upper level low. As Helene pushes NE, the upper level low is
forecast to retrograde across our area. This will place us
squarely between the upper low and Helene, creating an enhanced
area of convergence as both will be contributing to SE flow. SE
flow will continue to pull in warm, moist tropical air and could
support an additional threat for very efficient rainfall
production. The impacts from this could lead to an increased flash
flooding threat Friday morning, yet this threat materializing
remains uncertain. We will be monitoring how both of these
concerns play out over the next several day yet the bottom line up
front front is concerns for flash flooding and river flooding
from Helene with our area of highest concern being NE AL. Make
sure to have multiple ways to receive warnings.

Rain will continue for most of the day on Friday yet chances will
quickly drop off Friday evening as Helene continues on her
northward journey. Lingering SE flow will support a low chance of
rain through the remainder of the short term but the flash
flooding threat will likely have ended.


&&

.LONG TERM...
(Friday through Monday)
Issued at 233 AM CDT Tue Sep 24 2024

The forecast going into the Long Term portion will of course be
dependent on the eventual track of the tropical system, but the
rainfall impacts to the area may transition more to the upper low
over the Mid South/lower MS Valley regions as opposed to the
remnant tropical system exiting to the ENE. Medium chances for
showers/tstms (30-50%) are expected on Fri, as the upper low
begins to drift eastward. However, given the slower movement of
this feature, rain chances look to taper off this weekend to
around 20-30%. In fact, any additional rainfall looks to remain as
showers, although an isolated storm cannot be ruled out Sun
afternoon. With less cloud cover/rainfall, highs this weekend look
to climb back into the lower 80s/near 80F. Those rain chances
increase slightly on Mon, as the upper low begins to lift into the
OH Valley area. Highs on Mon also look to trend more in the upper
70s/near 80F. Lows this weekend and into next week look to remain
in the lower/mid 60s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1158 AM CDT Tue Sep 24 2024

VFR conditions will start the TAF period. An approaching cold
front will support showers and thunderstorms this afternoon. As
showers and storms move through ceilings and visibilities will
likely drop into periods of MVFR. Heaviest rain and storm chances
look to be from 20-0Z, thus a tempo group was included for both
terminals to reflect MVFR potential. After sunset, storms will
wane with rain forecast to continue through the night. While the
current forecast keep VFR conditions in the TAF through the
remainder of the period, we will continue to monitor trends
overnight to see if prolonged MVFR conditions develop.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&

$$

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