152
FXUS64 KHUN 191728
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1228 PM CDT Sat Sep 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1045 AM CDT Sat Sep 19 2026

 - Conditions will be favorable for strong-severe thunderstorms
   each afternoon Today-Tuesday, with the greatest spatial
   coverage of storms expected Monday and Tuesday. Locally
   damaging downburst winds, frequent lightning and heavy rainfall
   will be the main storm impacts.

 - Hot temperatures will continue from Today-Monday, with highs in
   the mid-upper 90s in the valley. A Heat Advisory remains in
   effect through 8 PM CDT today.

 - A slightly cooler and drier airmass will arrive late in the
   forecast period, with highs dropping back into the 80s on
   Thursday/Friday.

&&

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 1045 AM CDT Sat Sep 19 2026

A number of changes were noted with the upper level pattern in
comparison to earlier this week. A former "mega" upper ridge that
helped bring the heat to much of the central, southern, and
eastern Lower-48 has weakened with maximum 500mb heights around
593 decameters over the AR-LA-TX-OK region. A TUTT type upper
low was moving westward across the far NE Gulf of America. This
Tropical Upper Tropospheric Trough feature should remain over the
eastern Gulf into early next week. A weaker upper disturbance over
eastern Kentucky was producing weak troughing extending southward
along the AL/GA border. Otherwise, mainly sunny skies prevailed
at 10 AM with temperatures climbing through the 80s with light
winds.

Strong daytime heating and resultant instability will result in
scattered to at times broken fields of CU and some TCU. Moderately
high precipitable water of amounts from 1.6-1.8" with heating will
result in most unstable CAPES rising 1500-2200 J/kg late this
morning and early this afternoon. Thus low/medium chances of
showers and thunderstorm will be realized mainly in the afternoon.
Per convective outlooks from the SPC; some of the storms over our
more eastern areas could become strong to severe. The main threat
from the stronger storms will be downburst-type outflow wind
gusts. The best chances for the stronger storms will be more to
our east. WINDEX numbers and an inverted-V signature from forecast
soundings confirm a strong outflow wind potential.

Heat is another concern for today. Before showers commence, expect
another hot day with highs rising into the mid/upper 90s, with a
100 degree reading over NW Alabama. Over the past few days, strong
surface heating has mixed dewpoints from the 70s into the 60s,
which has put a damper on heat indexes rising into the advisory
area. Unless newer guidance suggests otherwise, we are planning to
let the Heat Advisory expire at 8 PM this evening. After shower
activity ends this evening, expect another muggy night with lows
from near 70 east to the low/mid 70s near large bodies of water.
As we go to the end of the summer season, longer nights under
mostly clear skies could allow the development of fog before
daybreak Sunday, and mainly in/near areas that receive wetting
(greater than 1/10") rainfall and/or in fog favored areas.

&&

.SHORT TERM...
(Sunday through Tuesday)
Issued at 1045 AM CDT Sat Sep 19 2026

The upper disturbance to our NE will move further to the east on
Sun, while the upper ridge to our west and low over the NE Gulf
remains. Thus another hot day expected. Highs should rise into the
low 90s east to mid/upper 90s west. Dewpoints in the 70s again
should mix down into the 60s, thus are expecting heat indexes to
remain less than 105 degrees. Despite no advisory, area residents
should maintain awareness for the heat. The mixing should also
lower shower/thunderstorm chances in the afternoon. Will keep low
chances of afternoon convection for our more eastern areas, that
will be helped by more rugged terrain. Similarly mild/warm Sun
night with lows in the low/mid 70s.

A synoptic scale system forming to our west will approach the
Tennessee Valley on Monday. This system will bring low/medium
chances of showers/thunderstorms. With better forcing from this
system, storms that form could become strong to severe, with more
downburst-type outflow wind gusts the main threat. This risk has
been noted by the SPC, with most of the area in a Marginal (1 out
of 5) Risk for severe storms. Before showers begin, expect
similarly hot conditions with highs mainly in the 90s (lower 90s
east to mid/upper 90s west). It should be bit cooler Mon night
with lows from the mid 60s east to lower 70s near large bodies of
water. Scattered to numerous showers and thunderstorms are
forecast Tuesday, with highs from the upper 80s east to mid 90s
west. Confidence is too low this far out to exactly discern storm
strength; cannot rule out stronger storm chances Tue. Lastly, the
Autumn 2026 season begins Tue evening around 704 PM CDT.

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 1057 PM CDT Fri Sep 18 2026

Latest extended range forecast data suggest that a weak northern
stream trough will advance slowly eastward from the Mid-MS Valley
into the northern Mid-Atlantic states next week, as it will likely
be blocked by ridging to its north. At the surface, a trough
(initially extending from central parts of MS/AL north-
northeastward into the Upper OH Valley) is predicted to remain
nearly stationary on Tuesday, and will likely focus development of
additional showers and thunderstorms across our region both
during the day and at night. In similar fashion to Monday, a few
strong-severe thunderstorms may occur during the afternoon and
evening hours, aided by high CAPE and increasing W-NW flow aloft.

Although there is some uncertainty regarding precisely when this
will occur, the surface trough is expected to shift slowly
southeastward at some point Wednesday/Thursday, allowing a
cooler/drier airmass (originating from an anticyclone across
southern QC) to spread southeastward into the region. This coupled
with 20-30 knot W-NW flow aloft and dry advection through the
depth of the tropospheric column will allow rain chances to
decrease considerably on Thursday/Friday. Afternoon highs will
fall back into the l-m 80s by the end of the work week, with
overnight lows Thursday night/Friday morning in the u50s-l60s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1228 PM CDT Sat Sep 19 2026

Strong daytime heating and resultant instability has resulted in
the development of isolated to scattered showers and thunderstorms
around the TN Valley. Most of this activity was forming in the
higher terrain. General movement of the convection was SSE around
5kt. Given development trends, have kept a PROB30 in for both
terminals this afternoon and early evening. Storms will be capable
of producing strong to severe microburst type wind gusts and heavy
downpours, with brief reductions of CIG/VSBY to MVFR and lower.
Convection should wane as we go into the evening with VFR weather
returning. However late in the night and early Sun morning,
cannot rule out patchy fog. It will be more likely in/near places
that received recent heavy rainfall.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Heat Advisory until 8 PM CDT this evening for ALZ001>010-016.

TN...Heat Advisory until 8 PM CDT this evening for TNZ076-096-097.

&&

$$

NEAR TERM...RSB
SHORT TERM....RSB
LONG TERM....70
AVIATION...RSB