166
FXUS64 KHUN 180726
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
226 AM CDT Sat May 18 2024

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

.NEAR TERM...
(Today)
Issued at 226 AM CDT Sat May 18 2024

Much of the Tennessee Valley region remains under the influence
of southwesterly flow. A surface front has moved slightly north
into southern Mississippi and southern Alabama this morning. A
weak surface low has formed along it near the Hattiesburg, MS
area. The most widespread area of showers and thunderstorms has
been developing near and south of this surface front.

In the upper levels of the atmosphere, a longwave trough axis lingers
to the northwest of it and stretches from the central Great Lakes
region SW into central Arkansas and eastern Texas. Models finally
show this trough axis aloft moving east this morning into the
afternoon hours. As this occurs, would expect convection to our
south to be guided ENE via the predominate flow pattern in place
and additional showers and thunderstorm activity begin to develop
around daybreak and continue into the afternoon hours, as the
trough axis and a weak developing upper low aloft move east
through the area.

The strength of the storms that will develop this morning into the
afternoon hours is not very clear. However, that being said, there
is a enough shear in place especially this morning into the early
afternoon hours to warrant a low end threat for severe storms. The
0-6 km shear really weakens by the mid afternoon timeframe (less
than 25 knots). However, instability after 2 PM may climb to a bit
above 2000 J/KG. Not great DCAPE values later in the afternoon,
but with some models hinting at 7.5 degrees/km mid level lapse
rates and that much CAPE - severe storms could last into the late
afternoon hours (mainly east of the I-65 corridor). The main
threats with any severe storms looks to be large hail and damaging
winds. Hail might end up being the more realizable threat
overall. Cloud cover and expected convection today should keep
temperatures from climbing much above the mid to upper 70s.

The main period of potential for severe weather at this time looks
to be between 9 AM and 2 PM for areas west of the I-65 corridor.
For locations further east, a window of noon to 6 PM looks more
likely.

&&

.SHORT TERM...
(Tonight through Tuesday)
Issued at 226 AM CDT Sat May 18 2024

Most guidance moves the upper low and upper level trough axis into
northern Georgia and southern Alabama this evening. Wrap around
shows and a few embedded thunderstorms could persist though in
northern Alabama and southern middle Tennessee. These storms
should not be severe given the lack of shear present and declining
instability. These showers and thunderstorms could last until
around midnight before pushing further east into Georgia.
Slightly drier air behind the departing trough axis and surface
front should allow lows to drop into the 60 to 65 degree range as
you wake up on Sunday morning.

Guidance continues to move this upper low east and drag the
surface front southeast through the day on Sunday. The result
should be a nice day across much of northern Alabama and southern
middle Tennessee. Some morning clouds should give way to mainly
partly cloudy skies in the afternoon. Clouds and a 20 to 30
percent chance of an afternoon shower or thunderstorm will pop
back up far eastern portions of Alabama (due to the back edge of
forcing from the upper low to our east/afternoon instability). Not
expecting to see much development though or any of these storms
if they develop to become severe. This insolation should allow
highs to climb back into the lower to mid 80s.

Sunday night light winds and clear skies are expected across the
area. This could allow lows to drop into the upper 50s to lower
60s. A warmup begins on Monday, as strong upper level ridging
starts to build over the area. 925 mb temperatures climb into the
lower 20s in the afternoon. With sunny skies, temperature will
likely climb into the mid to upper 80s (maybe a tad higher).

&&

.LONG TERM...
(Monday night through Friday)
Issued at 226 AM CDT Sat May 18 2024

Dry and warm conditions will continue into Tuesday, as upper level
ridging amplifies over the area. Highs should approach 90 degrees
in a few places. Lows should only drop into the mid 60s to near
70 Tue night.

A storm system forecast to form over the Rockies and adjacent
High Plains over the weekend will head to the NE, reaching the
Great Lakes on Wednesday. A cold front trailing south of it will
move across the area on Wed. Moisture convergence and lift
preceding it will return medium chances (30-50%) of showers and
thunderstorms beginning Tue night. Unsettled weather with
scattered showers and thunderstorms will remain in the forecast
into Thursday. Overall storm strength should remain "general" with
a risk of strong outflow wind gusts, heavy downpours, and sudden
and/or frequent lightning. Even with more clouds and rain chances,
high temperatures on Wed/Thu should range in the mid/upper 80s,
and lows in the 60s.

&&

.AVIATION...
(06Z TAFS)
Issued at 1135 PM CDT Fri May 17 2024

Calm or very light winds are in place at the terminals at this
time. Cloud cover is in place and should become thicker after
8Z/9Z. This should keep fog from becoming dense. However, with a
boundary in place near the terminals helping focus higher moisture
in the boundary layer, some MVFR to IFR fog could occur through
8Z at KMSL and 9Z at KHSV. Fog should improve but MVFR VSBYS or
CIGS will likely remain in place towards daybreak. A good chance
of -TSRA are expected to develop between 8Z and 13Z at both
terminals, so a tempo group for -TSRA was included with IFR VSBYS.
A more predominant period of -SHRA and VCTS is expected after 15Z
at both terminals with another period of heavier TSRA between 17Z
and 22Z.

&&

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

$$

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