988
FXUS63 KDMX 201137
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
637 AM CDT Mon Jul 20 2026

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Hot and humid today with heat index of 100-105+ this
  afternoon. A heat Advisory is in effect from noon - 8pm.

- Strong to severe storms are expected this afternoon and
  evening. Damaging wind and hail are the main hazards, along
  with pockets of heavy rain. There is a low tornado threat
  mainly in northeast Iowa.

- Cooler temperatures in the low 80s this week behind the cold
  front.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 301 AM CDT Mon Jul 20 2026

The upper level shortwave through has made it to North Dakota and
northern Minnesota overnight with a cold front trailing to the
southwest. The low level jet has increased ahead of the shortwave,
fueling overnight convection that has push across South Dakota and
into southern Minnesota early this morning. The LLJ has brought a
plume of moisture back into the upper midwest and convection is
traveling along this gradient. Expect storms to continue moving
to the southeast through the morning, clipping parts of
northeast Iowa towards sunrise. While this cluster of storms
produced severe winds earlier, is has since diminished in
intensity. This trend is expected to continue this morning with
the LLJ weakening through sunrise. Even so, a few stronger gusts
are possible.

Conditions clear out behind these morning storms in northern Iowa
with strong theta e advection into the area. This will make for
another hot and humid day, the hottest of the recent warm spell.
Heat indicies this afternoon are expected to reach 100-105+ across
most of Iowa. The approaching shortwave should help to push wildfire
smoke back east of the area for most of today.

Storms are expect to develop on the cold front that will make it to
northern Iowa by this afternoon. A few isolated airmass
thunderstorms are possible on remnant outflow boundaries in
northern to northeast Iowa midday into the early afternoon ahead
of the main front. Instability builds with strong theta e
advection into the area and MLCAPE reaches 3000+ J/kg in
northeast Iowa by the afternoon. There is 50+ kts of 0-6 km
shear to organize updrafts, with initial supercell and cluster
thunderstorms anticipated before growing upscale along the
front. Lapse rates are modest at 6-7 C/km, diminished by warmer
mid level temperatures. In northeast Iowa 0-1 km SRH reaches
100-200 m2/s2 with 0-3 km SRH 300+ m2/s2. This increased the
tornado potential in that part of the state, especially as
storms initiate. Low level CAPE is somewhat lacking at under
100 J/kg for 0-3 km which may inhibit the low level stretching
potential. As storms grow upscale and push into central and
southern Iowa this evening wind will be the primary hazard. The
cold front finally sinks south of the area early Tuesday
morning. Pockets of heavy rain are possible with storms owing
to PWATS around 2" and warm cloud depths of 3500+ m. Dry
antecedent conditions and mature crops should mitigate most
hydro concerns.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 318 PM CDT Sun Jul 19 2026

Showers and thunderstorms will likely carry primarily a wind threat
into the night, before decreasing near/after sunrise. With the front
through the majority, if not all of Iowa, northwest flow and cool
advection will spread across Iowa, leading to slightly cooler
temperatures and drier air. With this shift in the flow, HRRR smoke
guidance indicates the return of wildfire smoke into Iowa from
Minnesota, leading to additional hazy skies and at least some
possible lowering of visibilities. Surface high pressure though will
lead to dry conditions through the rest of the day as this feature
descends across the Central Plains and through much of Wednesday.
Conditions will remain comfortable through midweek as northwest flow
remains, with temperatures largely in the upper 70s to 80s and
dewpoints in the 50s to low 60s. A weak wave skimming southwest Iowa
Wednesday evening looks to bring returning chances for rain and
possible thunderstorms, while additional waves riding the upper
level flow follow this activity that will bring additional periods
of active weather through late work week. Details regarding these
systems will be better known in the coming days. Ridging then builds
over the southwestern CONUS that will slowly influence temperatures
through the weekend as highs gradually return into the 90s.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 637 AM CDT Mon Jul 20 2026

Thunderstorms are moving across northern Iowa with impacts at
KMCW/KALO for the next few hours. After a break in the middle of
the day a second round of thunderstorms will move across the
area with a cold front this evening and through the end of the
TAF period. Thunderstorms are most likely at sites KALO/KOTM
with -TSRA is prevailing, though scattered convection along the
cold front may also impact KDSM. Behind the cold front wind
shifts to out of the northwest and smoke settles across the
area through Tuesday morning.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 8 PM CDT this evening for
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.

&&

$$

SHORT TERM...Hagenhoff
LONG TERM...Bury
AVIATION...Hagenhoff