667
FXUS63 KDMX 220350
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1050 PM CDT Mon Jul 21 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Thunderstorm potential and cloud debris preclude heat
  headlines for now. Should the warm front lift through the
  state, heat index values of 100-110 may occur by the
  afternoon.

- Hot and humid Wednesday.

- Thunderstorms possible again Wednesday night into Thursday.

&&

.DISCUSSION...
Issued at 258 PM CDT Mon Jul 21 2025

Surface warm front is just south of Iowa over far southern Nebraska
and into northeast Kansas and southeast towards Kansas City. This
boundary has been active all day with ongoing convection which has
produced heavy rainfall but also has kept high temperatures in the
low to mid 70s. On the north side of the boundary, widespread
stratus/stratocumulus over the state. The elevated mixed layer (EML)
remains stout over central Iowa though some elevated convective
bubbling has occurred into central Iowa. A bit more established
elevated convection is ongoing over southern Minnesota which a few
fragments have reached far north central Iowa.

The boundary will lift into Iowa tonight and on Tuesday. There
remains a fair amount of uncertainty regarding the forecast going
into Tuesday regarding convective trends. Upper ridging is building
north into Tuesday otherwise the overall upper level flow does not
support a strong push of the warm front northward and models tend to
push these features too fast north. Therefore, expecting a slower
warm front movement across central Iowa resulting in thunderstorm
chances for at least part of the day. The potential convection and
any convective debris will have an impact on high temperatures and
also the heat indicies for Tuesday. If sunshine occurs and the
boundary lifts north, heat index values will be in the 100 to 110
degree range south of the boundary. On the opposite end of the
spectrum, there is also a low chance of widespread thunderstorms
with the potential for heavy rain. Due to the uncertainties, will
push headlines decisions off for now and it may need to be a short
lead time headline. Will continue to advertise heat potential with
the storm caveat. A localized severe storm with damaging winds and a
few pockets of heavy rain are possible tonight into Tuesday.

We have a greater confidence in heat on Wednesday as Iowa should be
in the warm sector at that point with highs in the 90s and dewpoints
in the 70s. This will place heat index values at 100 to 110 degrees.
The upper level ridge will pass off to the with the upper flow
becoming southwesterly Wednesday night into Thursday which will
allow a boundary to drop back into the state. That boundary will be
the focus for more storms and it tis the season for heavy rain
potential should storms training along the boundary. Otherwise the
parameters are in place for efficient rain processes. A typical July
weekend looks on tap while the upper level ridge becomes re-
established just west of the area by early next week. That may place
Iowa in the northeast quadrant and possibly withing the MCS ring of
fire zone.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1050 PM CDT Mon Jul 21 2025

High clouds continue to spread across the state from a storm
system all the way in Kansas. Meanwhile, MVFR to IFR stratus is
expanding across northeast Iowa. This will impact sites
KMCW/KALO/KFOD through Tuesday morning, and further reduction to
LIFR is possible. At the same time, patchy light fog
development is becoming more likely and have included mentions
at KMCW/KALO. Clouds diminish late Tuesday morning, along with
increasing south winds. Isolated thunderstorms are also
possible late afternoon into the evening, however there is
little consistency in model data regarding placement so have
kept from TAFs at this time.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Hagenhoff