112
FXUS64 KHUN 181645
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1145 AM CDT Fri Sep 18 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 1007 AM CDT Fri Sep 18 2026

 - A Heat Advisory is in effect through 8 PM Saturday across all
   of southern middle Tennessee and northern Alabama.

 - NWS Heat Risk highlights Moderate (Level 2/4) to Major (Level
   3/4) heat impacts through the weekend across the Tennessee
   Valley. Localized Extreme (Level 4/4) impacts may occur in
   urbanized areas.

 - A Marginal Risk (Level 1 of 5) for strong to severe
   thunderstorms exists Saturday afternoon and evening for gusty
   to damaging downburst winds.

&&

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 1007 AM CDT Fri Sep 18 2026

A stout ridge, 564 dam at 500 mb, will remain the dominant
feature across our area through the near term. This will keep most
of the CWA hot and dry today.

With high temperatures expected to be in the mid to upper 90s and
NWS HeatRisk in the Moderate to Major (level 2-3 of 4) category,
A Heat Advisory will remain in place area wide. With vertical
mixing expected to keep dew points in upper 60s to lower 70s,
maximum heat index values are expected to be around 100 to near
105 degrees.

With the core of the ridge shifted a bit west today, thinking we
may see a bit more in the way of afternoon convection compared to
previous days. Current expectations are for mainly low (15-20%)
chances primarily across our higher terrain in the east. Storms
that do form will move from NE to SW and could produce wind gusts
in the 40-50 mph range given DCAPE values over 1000 J/kg and
inverted V soundings. It may sound like a broken record at this
point, however be heat smart: slow down, cool down, stay hydrated
and NEVER leave people or pets in vehicles. Tonight, temperatures
slightly cool into the low to mid 70s.

&&

.SHORT TERM...
(Saturday through Sunday night)
Issued at 1007 AM CDT Fri Sep 18 2026

Conditions will remain hot through the weekend as the TN Valley
sits under strong upper ridging and while an upper low begins to
retrograde over the eastern Gulf. This will provide additional
support for diurnal showers and thunderstorms on Saturday, and
model soundings show a good amount of mixing/dry air in the low
levels Saturday afternoon. DCAPE values in excess of 1100 J/kg
will support the threat for microbursts as highlighted by a
Marginal Risk (level 1 of 5) by the SPC. Afternoon highs near 100
degrees will create a dual threat for those with outdoor plans,
and the Heat Advisory will remain in effect through 8 PM tomorrow.
While the synoptic pattern stays largely unchanged on Sunday,
slightly lower atmospheric moisture will keep PoPs on the low side
(<30%) and confined east of I-65. Highs on Sunday will once again
approach 100 degrees with heat indices reaching 105F in some
urban locations. Please protect yourself and others from the
dangerous heat this weekend and remain weather aware if spending
time outdoors!

&&

.LONG TERM...
(Monday through Thursday)
Issued at 930 PM CDT Thu Sep 17 2026

Extended range model solutions suggest that a 500-mb ridge will
remain positioned across the forecast area on Monday. However, as we
progress through the rest of the period, it is becoming increasingly
likely the the southern edge of the mid-latitude westerlies will
develop southward into our region, with indications of a flat
subtropical ridge lying across the northern Gulf and development of
an upper low (from phasing of 2-3 distinct northern stream
shortwaves) over the Great Lakes. In the low-levels, a weak area of
low pressure is predicted to migrate from the Mid-South into the TN
Valley on Monday, before degenerating into a frontal wave as it lifts
northeastward into the Upper OH Valley Monday night. Although the
trailing cold front will make only gradual southeastward progression
into the Ozarks and OH Valley by early Tuesday morning, mesoscale
boundaries originating from extensive convection to our northwest
should contribute to a higher coverage of thunderstorms across our
CWFA Monday afternoon and evening. As surface pressures begin to rise
within a high migrating eastward across southern Ontario/Quebec (and
renewed cyclogenesis takes place over the eastern Great Lakes), the
cold front will advance further southeastward on Tuesday, resulting
in another episode of convection during the afternoon/evening hours.
Sufficient CAPE will exist to support a risk for strong-locally
severe thunderstorms both periods, especially given an increase in
mid-level flow to 15-25 knots. As the cold front shifts further
southeastward through the region Wednesday, light-moderate northerly
flow will begin to advect a slightly cooler/drier airmass into the
region, with highs on Wednesday and Thursday dropping back into the
85-90F range and lows falling into the l-m 60s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1145 AM CDT Fri Sep 18 2026

VFR conditions are forecast through the TAF period with a low
chance for a few exceptions. First, a low chance for thunderstorms
will exist over NE AL today, some of which may spread far enough
west to impact the HSV terminal. Confidence in this is very low at
this time, so did not include any mention of TSRA in the TAFs but
amendments will be made if radar trends warrant. Secondly, there
will be a low chance of fog formation early Saturday morning
which could impact either TAF along river valley areas.

&&

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

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

&&

$$

NEAR TERM...HB
SHORT TERM....25
LONG TERM....70
AVIATION...25