784
FXUS63 KDMX 310415
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1115 PM CDT Sat Aug 30 2025

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

.KEY MESSAGES...

- Stretch of sunny skies coming to an end as a cloudy and
  unsettled period takes shape. Beginning with rain chances
  (20-40%) today. Three day rainfall totals at or above 1"
  possible mainly in western and southern Iowa.

- Fall-like air mass settles in for the middle/end of the week,
  with high temperatures not making it out of the 60s and low
  temperatures dropping into the 40s - a few areas in northern
  Iowa may even drop into the upper 30s!

&&

.DISCUSSION...
Issued at 221 PM CDT Sat Aug 30 2025

Weakly sheared pattern dominates much of the CONUS, with one
ridge of high pressure drifting southeast from the Canadian
Prairie Provinces towards the Great Lakes; while a second is
entrenched across the western U.S. In between these two
features, resides a nearly stationary elongated area of
shortwave energy. This feature will be the culprit for bringing
an end to the recent run of sunshine, ushering in clouds and
rain chances that will likely stick around through the first
half of next week.

Satellite pix depict pockets of agitated cumulus already
developing across the CWA along with residual subtle
differential heating boundaries. KDMX 88D not showing anything
at this point - however expect that to change over the next few
hours as convective temps are met, sparking popcorn convection
across portions of central Iowa. Primary hazard will be lighting
with this activity, however sufficient 0-3km CAPE and surface
vorticity coupled with boundaries in the vicinity and weak
shear, will once again see an increased potential for weak
funnels this afternoon/early evening. If funnels do manages to
develop would be weak and not expected to touch the ground. No
severe weather is expected. Convection will wane along this band
with loss of daytime heating, just in time for the next push of
moisture associated with the aforementioned shortwave energy to
work in from the west tonight.

The pattern doesn`t change much Sunday-Monday with this slow-
to-move blocking pattern in place across the region. However,
the shortwave will be slightly closer on both days and as such
expect a better eastward push of moisture, thus increasing
shower/thunderstorm chances across western and central Iowa.
Widespread clouds will hold temperatures down as well, with
highs mostly only reaching into the low 70s both days.

The blocking pattern finally breaks down for Tuesday kicking the
shortwave energy out of the region, allowing what will be a very
fall-like air mass, with origins in the arctic to dive into the
state. So expect high temperatures only reaching the 60s
Wednesday and Thursday, with overnight lows dropping generally
in the 40s (perhaps even some 30s across northern Iowa!).

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1107 PM CDT Sat Aug 30 2025

A few lingering showers over central Iowa will continue to
dissipate this evening. Meanwhile, the area of rain over
southwest Iowa will persist and migrate very slowly to the
northeast. Little impact is expected from this rain overnight,
with confidence increasing that it will approach DSM, FOD, and OTM
in the latter part of the TAF period. Concern at northern sites
is potential for fog overnight again where the cirrus is thin.
With the stagnant air mass in place, could see similar
visibilities as last night at MCW and ALO in particular.

&&

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

&&

$$

DISCUSSION...Hahn
AVIATION...DMD