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645
FXUS64 KHUN 050234
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
934 PM CDT Sat May 4 2024

...New NEAR TERM...

.NEAR TERM...
-- Changed Discussion --
(Rest of tonight)
Issued at 934 PM CDT Sat May 4 2024

More tranquil weather has returned across the Tennessee Valley, as
convection over our eastern areas have exited to the east. Other
showers were in progress over the Ozarks and fading over western
Mississippi. 9 PM temperatures have cooled into the upper 60s to
lower 70s, after earlier rising into the upper 70s and lower 80s.

Unlike last night, skies across the region were mostly clear, with
a few passing cirrus clouds. Thus with a moist surface, the clear
skies, light winds, lower rain chances and the night-time; brings
a risk of fog developing. Model MOS guidance was showing this,
especially the GFS and GFS-based LAMP, while the older NAM was
only showing patchy fog at best. When refreshing the grids with
newer blended guidance (and lower rain chances/coverage) this has
generated more fog in the overnight. That said, I am not too
inclined for a Dense Fog Advisory at this time with shorter nights
and some inherent instability that could result in a stray
shower or two forming. Do have patchy to areas of fog in the
grids, based on new dewpoints and minor temperature adjustments.
Other places more subject for fog would be locations that received
measurable rainfall the past day or so, and those more sheltered
locations. Low temperatures otherwise should cool into the low/mid
60s by daybreak Sunday.
-- End Changed Discussion --

&&

.SHORT TERM...
(Sunday through Tuesday)
Issued at 319 PM CDT Sat May 4 2024

As a stronger disturbance moves north-northeast from northeastern
Texas and central Oklahoma late Saturday night into Sunday
morning, a warm front ahead of it moves northeast into northern
Arkansas by the mid-afternoon hours. Models form robust convection
along this warm front. However, most models only develop this
convection as far east as Mississippi through the afternoon hours.
This is a good thing given the sounding parameters further east
into northern Alabama. This will likely keep any severe thunderstorm
activity to the west of the area through the afternoon hours.
Models do push this warm front further north into northwestern
Alabama between 7 and 9 PM. However, models really drop off
instability these storms have to work with during that timeframe.
Shear continues to be too weak to support any severe weather.
Gusty winds, frequent lightning, and heavy rainfall could occur as
this weakening convection moves into the area and across northern
Alabama and southern middle Tennessee overnight. If this activity
along this warm front moves in sooner than expected, then a severe
downburst or large hail threat might materialize. However, this is
not expected as mentioned before.

Models weaken this upper level disturbance and have it move more
to the east Monday into Monday night. Not expecting as widespread
or strong thunderstorm activity this far south, with the main
energy with this disturbance remaining more over northern
Tennessee into the Ohio Valley. However, high chance to likely
chances of showers and thunderstorms should still remain in the
forecast through the day on Monday.

A drier pattern with zonal flow aloft is in place Monday night
through Wednesday. Very strong warm air advection develops ahead
of a strong cold front that develops over the central CONUS on
Tuesday. 925 mb temperatures between 23 and 26 degrees are
advected into the area ahead of the developing cold front well to
our west. This should allow temperatures to climb into the mid to
upper 80s during this period in the afternoon, despite some
isolated to scattered showers and thunderstorms. We could see
some highs around 90 degrees on Wednesday, but kept things a tad
cooler for now. These isolated to scattered showers or thunderstorms
should remain fairly unorganized, given low shear value and lack
of drier air aloft.

&&

.LONG TERM...
(Wednesday night through Saturday)
Issued at 319 PM CDT Sat May 4 2024

The more reasonable scenario for Wednesday evening into Thursday
continues to look like an MCS ahead of that stronger cold front
reaching our region by Wednesday evening. In this case,
redevelopment of thunderstorms would occur along the path of the
surface low (across MO) early Wednesday afternoon that could
potentially grow upscale into a larger and more significant MCS
that would move through our region late Wednesday night/early
Thursday morning. This convective system would be entering an
environment of even stronger deep-layer shear (with WSW flow aloft
of 45-50 knots) and moderate-high levels of instability driven by
surface dewpoints in the lower 70s beneath a plume of steep lapse
rates aloft. Thus, a notable risk of severe thunderstorms
producing large hail and damaging winds may materialize during
this timeframe. A third and final round of storms may occur on
Thursday night/Friday morning prior to the eventual passage of a
cold front that should bring a drier/cooler airmass into the
region by next weekend.

&&

.AVIATION...
(00Z TAFS)
Issued at 622 PM CDT Sat May 4 2024

Low chances (15-25%) of showers/storms will persist through this
evening, then diminish for the overnight period. Patchy fog is
possible at the terminals, with forecast MVFR conditions at HSV
and IFR at MSL later tonight; however, this will be reassessed at
the next TAF issuance for any potential of patchy, dense fog.
Confidence was too low to include in the TAFs at this time. Any
fog will then lift and dissipate through 14Z, with low to medium
(30-50%) chances of showers/storms to follow Sunday afternoon.
Winds will decrease to be light and variable tonight, then become
southwesterly at around 5 knots or so on Sunday.

&&

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

$$

NEAR TERM...RSB
SHORT TERM....KTW
LONG TERM....KTW
AVIATION...26