899
FXUS64 KHUN 261738
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1238 PM CDT Sun May 26 2024

...New AVIATION...

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 948 AM CDT Sun May 26 2024

Lots to talk about in the update this morning. While a majority of
our attention today will be on severe weather potential tonight,
another dangerous threat has consistently been presented in the
models for this afternoon that we must discuss: excessive heat.
HIRES models show greater than 90% chances of NW AL meeting or
exceeding 90 degrees today. While chances are slightly lower for
the remainder of the area (40-70%) those that don`t meet 90 will
still have highs in the upper 80s with real feel temperatures in
the low to mid 90s area wide. Today will likely be one of the
hottest days of the year so far thus, it is important to resume
practicing proper heat safety for anyone participating in outdoor
activities. This includes staying hydrated, wearing sun
protection, and taking frequent breaks in shaded or air
conditioned area.

As for our main severe threat, models have remained consistent in
a line of storms moving through the area from around midnight to 7
AM. All hazards remain the same with potential for damaging winds,
hail, and tornadoes. A full discussion of overnight environmental
parameters and threats can be found in the short term forecast
discussion. The remainder of this discussion will go over what
remains uncertain at this time. Ongoing convection well to both
our north and west will play a pivotal role in any pre frontal
convection today. If any outflow boundaries from ongoing
convection move into our area this afternoon, the environment will
be very favorable for supercells with all hazards possible. There
is very low confidence in this currently. The other parameters we
will be closely monitoring through the duration of the afternoon
will be the evolution of any CAP and presence of any directional
shear. These two parameters will pay a pivotal role in determining
our tornado threat overnight. Current models indicate the
presence of a CAP at the start of the line yet are inconsistent
in maintaining it or eventually degrading it. Likewise, models are
still inconsistent in favoring speed vs direction shear. If
directional shear begins to be favored and the CAP is able to
erode, this would increase our threat for embedded tornadoes. If
the CAP remains and speed shear prevails, straight line winds will
be our primary concern. Regardless, with this being an overnight
event, we want to make sure everyone has multiple ways to receive
warnings including ones that will wake you up while you sleep.

&&

.SHORT TERM...
(Tonight through Wednesday)
Issued at 351 AM CDT Sun May 26 2024

Tonight, a line of strong to severe storms is forecast to impact
the Tennessee Valley from the northwest ahead of a cold front.
Models have begun becoming slightly more consistent with timing
for this, bringing the line into NW AL and portions of southern
middle TN around 6Z and pushing it southeastward until it exits
the area by around 12Z. With this primary line, the following
threats will be possible: large hail (medium confidence), damaging
winds (medium confidence), heavy rainfall/flooding (low- medium
confidence), and tornadoes (low confidence). MUCAPE of 2000+ J/kg
in addition to steep mid level lapse rates (7.5-8.0 C/km) will
allow large hail to be a medium threat, however, with high PWATs
(1.5-1.9" per the HREF, which is above the 90th percentile for BMX
climatology), there is a potential for melting of large hail.
Damaging winds will be supported by DCAPE values reaching 900+
J/kg as well as increased shear (30-50 kts). While heavy rainfall
is likely, flooding may be mitigated by fast storm motion. Our
tornado threat remains a low confidence one due to a cap that is
consistently in model soundings. However, if the cap erodes,
tornadoes will be more of a threat due to backed sfc winds and a
low level jet (40-50 kts).

However, the HRRR is indicating a potential for an outflow
boundary to move in from the northwest around 1Z. If this occurs,
this would force our severe timing window to be earlier than
previously discussed. This would also change our initial storm
mode to be supercell clustering that would eventually upscale
into a linear form. This would increase rain totals and cause
concern for flooding due to runoff.

Regardless of the arrival time, we have medium confidence storms
will exit the area by 12Z with low-medium chances (20-40%) of
lingering showers behind the cold front. Dry weather should return
to the TN Valley Monday night with clear skies as sfc high
pressure filters in from the Mississippi Valley. Highs on Monday
and Tuesday are forecast to reach the 80s with overnight lows in
the upper 50s/60s. Wednesday will be slightly cooler, but still
warm, with highs in the upper 70s to low 80s.

&&

.LONG TERM...
(Wednesday night through Saturday)
Issued at 351 AM CDT Sun May 26 2024

As upper level ridging moves in from the Mississippi Valley
through end of the work week, dry weather and mostly clear skies
will continue to dominate the long term period. Friday afternoon
through Saturday, low chances (30% or less) of showers/storms are
possible as an upper level shortwave forms in the lower
Mississippi Valley. Otherwise, high temperatures during this time
are forecast to be in the upper 70s to 80s with overnight lows in
the 50s/60s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1238 PM CDT Sun May 26 2024

Mostly VFR conditions will prevail for the first half of the TAF
period. After 0Z is when we will see lower ceilings move in ahead
of a line of strong convection. The line will move through from NW
to SE from around 4-12Z. The leading edge of the line will be
associated with the strongest storms prevailing MVFR conditions
expected. Brief periods of IFR and even LIFR are possible as the
line moves through however confidence is low. After the line moves
through rain and storms will likely linger behind it for several
hours. While this will be significantly less intense than the
initial line, it will likely still lower ceilings and
visibilities. Conditions should begin to clear after 12Z with a
gradual return to VFR expected by 18Z.

&&

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

$$

NEAR TERM...RAD
SHORT TERM....HC
LONG TERM....HC
AVIATION...RAD