536
FXUS63 KDMX 302340
AFDDMX

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

 ...Updated for the 00z 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.

- Today`s primary storm hazard will be lightning. Similar to
  recent days, atmospheric conditions point to the potential for
  funnel clouds this afternoon once again.

- 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 /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 619 PM CDT Sat Aug 30 2025

Ongoing showers and storms are percolating along a web of weak
boundaries, bisecting Iowa from northwest to southeast. This
activity will weaken over the next 2 hours as night encroaches.
Overall VFR conditions A stubborn area of MVFR stratus
continues to impact KMCW, with all other TAF sites currently
VFR. With stagnant air mass over the area, there is again a
chance of fog development tonight, especially northern TAF sites
where cloud cover is less. Confidence is low, so will monitor
and update if needed. Otherwise, clouds will be on the increase
bringing periodic rain and storm chances through the TAF period
as system to the west progresses into the area over the next 24
hours.

&&

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

&&

$$

DISCUSSION...Hahn
AVIATION...DMD