989
FXUS63 KDMX 121752
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1252 PM CDT Wed Aug 12 2026

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Another chance of severe thunderstorms this morning with
  damaging wind being the primary threat. Isolated instances of
  large hail and locally heavy rainfall are also possible.

- Hot and humid conditions continue through today with heat
  indices nearing or just exceeding 100 degrees across southern
  and portions of central Iowa.

- More shower and storm chances tonight and tomorrow, with
  additional shower and storm chances through the weekend.
  Locally heavy rain and severe weather is possible, but details
  will be better assessed with time.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 315 AM CDT Wed Aug 12 2026

Showers and thunderstorms are again expected this morning and severe
weather is possible. A cluster of storms in southern South
Dakota/northern Nebraska is currently ongoing and moving towards
Iowa, with an expected arrival in western Iowa in the early morning
hours. As has been the case the past several nights, there is no
clear-cut solution with how things will evolve. The devil lies in
the details. Mesoanalysis shows a deeply unstable environment across
Iowa with a strong CAPE gradient farther to the west. This cluster
is expected to ride the CAPE gradient to the southeast, though it
has to fight mid-level convective inhibition. RAP analysis shows the
Low Level Jet (LLJ) is just now beginning to nose into Iowa.
Deterministic models show the jet strengthening around 7am/12z this
morning. As it does this, the cluster would be energized and begin
to build towards the northeast into central Iowa. Another part of
the uncertainty comes from a lack of moisture return. Moisture
transport shows some signal in the mid-levels, and mesoanalysis
hints at better moisture transport with the still-strengthening LLJ.
Another solution that would bring storms even farther north is if
storms are enhanced by shortwave energy ahead of the main cluster.
If everything materializes, there is a decent signal for a damaging
wind threat with this cluster as it moves through Iowa. Compared to
previous nights, confidence is much higher in the evolution of
storms.

Once storms clear the area, which should be around mid to late
morning, with the potential to be as late as 1pm/18z, hot and humid
conditions are expected with heat indices again approaching the 100
degree mark. There is more uncertainty in terms of heat than in
previous days, as storms are progged to track farther south than in
previous nights over the area forecast to be warmest, which could
lessen heat indices. Once again, atmospheric recovery is expected
through the day today, though capping is still going to be in place
to inhibit storms during the daytime hours. Otherwise, storm chances
once again return tonight driven by a shortwave that will move over
the area. Confidence with storms tonight looks much higher than
previous nights have been given a more pronounced shortwave. Severe
wind gusts are not out of the question with this setup, however the
signal for heavy and excessive rainfall looks the greatest with
decent moisture return and PWATs over 2 across the area. There is
still some disagreement with the specific location of where the
heaviest rain will fall. At the very least, flash flooding would be
a concern over any cities/towns.

Thursday looks to bring cooler temperatures to much of the state,
save for far southern Iowa. with temperatures in the upper 80s
across the south, and upper 70s to low 80s across north and central
Iowa. It may not be as dry, however, with the potential for showers
and thunderstorms through the day for at least some part of the
state along a boundary that looks to set up across central Iowa.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 249 PM CDT Tue Aug 11 2026

Active weather persists into Thursday night as another shortwave
traverse into the Plains, The SPC currently highlights the southern
CWA in a Marginal Risk (Level 1 of 5) for Thursday. The active
pattern remains in place through Saturday, maintaining low-end
severe storm probabilities. A more robust cold front will finally
sweep through the region on Sunday, bringing a cooler and drier
airmass. Highs look to top out in the upper 70s in northern Iowa to
lower 80s in southern Iowa.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1252 PM CDT Wed Aug 12 2026

Morning storms have exited east of the area with skies clearing
quickly behind. Scattered cumulus may develop this afternoon
but VFR conditions are expected. Overnight storms will reach
western Iowa, moving across Iowa in the early morning through
the end of the TAF period. Confidence in occurrence is fairly
high and -TSRA was included at all sites, but timing and
location could shift and adjustments in later issuances are
possible.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...67
LONG TERM...TDR
AVIATION...Hagenhoff