760
FXUS63 KDMX 252323
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
623 PM CDT Sat Jul 25 2026

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Dangerous heat will continue to build over the rest of the
  weekend into early next week, with a Heat Advisory in effect
  today, and a widespread Extreme Heat Warning Sunday. An
  Extreme Heat Watch remains Monday for potential continued
  heat impacts.

- Severe weather is possible late tonight into Sunday morning,
  and again Sunday evening into Monday morning. The primary
  concerns are damaging winds, large hail, and heavy rain.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 301 PM CDT Sat Jul 25 2026

After a morning filled with rather widespread dense fog and stratus,
conditions have greatly improved this afternoon, with satellite
imagery showing no fog and skies gradually clearing of clouds over
much of western and north/northeast Iowa. Due to the slow erosion of
stratus through the morning, temperatures were also slow to increase
in the 70s to low 80s, but since early afternoon with the increased
clearing are now rising faster with values through the 80s, warmest
west. The beginning of the well-advertised heat wave certainly has
begun given the presence of the western thermal ridge and a strong
push of low level theta-e advection into the state, with forecast
highs still expected to top out in the upper 80s east, while in the
low to mid 90s west, where the Heat Advisory remains in effect
through the rest of today.

Late tonight into early Sunday morning, model guidance continues to
signal a slowly decaying complex of elevated thunderstorms exiting
South Dakota/Nebraska and entering west/northern Iowa, roughly where
the increasing 30-40 knot low level jet is progged to be located and
where an instability gradient is indicated. As this activity
initially enters the state, the potential is in place for at
least some isolated severe weather, given MUCAPE values around
2000-3000 J/kg and wind shear values around 30-40 knots
overhead. The main hazard of concern would be damaging winds
given drier low levels with DCAPE values over 1500 J/kg and
steeper lapse rates around 7-8 C/km that could lead to hail
concerns as well. PWATS around 1.5-1.75 overhead, along with
notable warm cloud depths could also lead to heavy rainfall
where stronger storms develop, with isolated rainfall amounts up
to 1-1.5 inches, low concerns for back-building potential at
this time but something to monitor. Storm coverage should
decrease through the morning as this activity moves south and
east, with dry conditions expected to return for all areas mid-
late morning. Close monitoring on trends will be important this
evening on storm potential and coverage during this time, hence
only the addition of low PoPS further south and east through the
morning hours, with the potential for increasing these values
if confidence increases.

Despite the potential for showers/storms in the morning and cloud
cover, the further eastward movement of the thermal ridge Sunday
will allow for more widespread heat impacts across the forecast area
as stronger warm air advection moves into the region. Rather
uncomfortable overnight lows through the 70s will be followed by a
gradual increase in temperatures, especially into the afternoon as
skies clear, resulting in highs topping out in the mid to upper 90s.
These temperatures, along with forecast dewpoints in the upper 70s
overhead will lead to widespread heat indices in the 105-110 degree
range across the entire forecast area, making for a very hot and
humid day. The Extreme Heat Warning therefore stands, which is in
effect from 11am to 9pm Sunday. Those planning to spend time
outdoors should limit time in the sun, taking frequent breaks and
staying hydrated.

Sunday evening into Monday morning will feature the next potential
for another window of shower and storm activity over the region.
Guidance continues to indicate a more robust area of thunderstorm
activity from a passing weak shortwave riding the ridge into the
Upper Midwest, particularly over Wisconsin and Illinois where less
influence of the cap further west and closer proximity to the mid-
level feature is indicated. Forcing aloft during this time frame is
more notable and the LLJ surges further into portions of Iowa and
Minnesota, where deterministic models are now suggesting
another MCS developing over eastern Nebraska/South Dakota into
western Iowa, and tracking east southeast across the state
through the morning hours. Favorable instability and shear
profiles overhead will support another potential for severe
weather, though lesser certainty is in place given more of a
presence of the strong cap over these areas. If storms do
develop, damaging winds and large hail would again be possible
given dry low levels and steep lapse rates. Heavy rain is also
in play with this activity into Iowa, given PWATS around 2-2.25
inches and a tall, skinny CAPE profile. Refinements are expected
to continue with future forecast updates into Sunday.

If storms do move across the forecast area into Monday morning over
a larger portion of the forecast area, the potential for continued
widespread heat impacts could be limited somewhat. However, this
would likely at most be a few degrees less for highs in spots where
storms linger the longest and clouds remain. For now, maintaining
forecast highs in the mid to upper 90s and heat indices over 100
degrees in most areas, with no change in the Heat Watch given this
lingering uncertainty.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 301 PM CDT Sat Jul 25 2026

As the aforementioned trough deepens as it tracks over the
Great Lakes into the Ohio valley late Monday into Tuesday, will
see a push of cool air advection into Iowa that will end the
stretch of sweltering heat. While temperatures will only be a
touch cooler in the upper 80s to low 90s Tuesday, drier air from
this shift in low level flow turning northwesterly will allow
for slightly lower dewpoints in the upper 60s for most areas.
The western thermal ridge overall will move very little through
much of the work weak, with any precipitation chances signaled
to largely remain west of Iowa until around Thursday, when a
more potent shortwave dives southeast on the eastern fringe of
this ridge from the Dakotas into Iowa. Certainly room for slight
shifts in these larger scale features to occur in the coming
days given this being further out in the forecast period, so
stay tuned for updates. Highs through the rest of the week
remain generally in the upper 80s to low 90s, paired with
dewpoints in the 60s, more towards normal summertime averages.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 623 PM CDT Sat Jul 25 2026

MVFR ceilings over MCW and ALO will be departing very early in
the period yielding VFR conditions much of the night. Light,
patchy fog may develop over the eastern terminals of MCW, ALO,
and OTM towards Sunday`s sunrise so have continued fog/BR
mention. There is also uncertainty in how thunderstorms
presently over central South Dakota will move into Iowa late
this evening/tonight. While there is no mention at MCW, FOD, or
ALO, will be monitoring trends for possible AMD for PROB30,
TEMPO, or prevailing groups depending on evolution. Outside of
overnight storm chances and fog, VFR conditions are expected to
prevail beneath some high level smoke that will drift back over
the state on Sunday.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until noon CDT Sunday for IAZ004>007-015>017-
023>026-033>037-044>048-057>060-070>073-081-082-092-093.
Extreme Heat Warning from noon to 9 PM CDT Sunday for
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.
Extreme Heat Watch from Sunday evening through Monday evening
for IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.

&&

$$

SHORT TERM...Bury
LONG TERM...Bury
AVIATION...Ansorge