-- Discussion containing changed information from previous version are highlighted. --
479
FXUS64 KHUN 042019
AFDHUN

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

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

.NEAR TERM...
-- Changed Discussion --
(Tonight)
Issued at 319 PM CDT Sat May 4 2024

Some isolated to scattered showers or thunderstorms could end up
diving SSE from our southern middle Tennessee counties into
portions of northeastern Alabama through 7 or 8 PM. However,
coverage should be on the low side (30-40%) at best. Although
some instability (1000-2000 J/KG is in place in this area, lapse
rates and DCAPE is very meager. With no shear in place, only
expect typical garden variety of thunderstorms producing heavy
rainfall and some lightning.

Expect this activity to become very isolated after 9 PM and mainly
occur near the AL/GA border. Winds will be fairly light 2 to 6
mph much of the night. Expect mostly clear skies much of the
rest of the evening into the overnight hours. This should allow
some fog formation, but winds should be just high enough to kept
it isolated in nature.

Decent radiational cooling conditions should allow temperatures
to drop to or just above dewpoint values though. Thus, expect lows
to end up between 60 and 65 degrees in most locations.
-- End Changed Discussion --

&&

.SHORT TERM...
-- Changed Discussion --
(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.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(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.
-- End Changed Discussion --

&&

.AVIATION...
(18Z TAFS)
Issued at 1247 PM CDT Sat May 4 2024

Primarily VFR CIGS are expected through 22Z. However, some MVFR
CIGS could occur, so a tempo group for that was included. A low
chance (PROB30) for -TSRA exists from 22Z through 03Z at KHSV. Not
expecting this possibility further west at KMSL. Fog may be a
possibility at both terminals, but left out for this issuance.
Some may be added in subsequent issuances.

&&

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

$$

NEAR TERM...KTW
SHORT TERM....KTW
LONG TERM....KTW
AVIATION...KTW