422
FXUS63 KDMX 250823
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
323 AM CDT Fri Sep 25 2026

.KEY MESSAGES...

- Another cool, cloudy, and wet period expected through Sunday.
  Expect several rounds of rainfall along with a few embedded
  thunderstorms. No severe weather is expected.

- High confidence /70-100%/ that portions of Iowa will receive
  over 1+" of rainfall by Sunday with portions of western and
  southwestern Iowa having a 30-70% chance of seeing 2+".

- Another strong storm system expected Tuesday and Tuesday
  night. Thunderstorms with additional heavy rainfall possible.

- Temperatures generally remaining below average due to clouds
  and precipitation with highs in the 60s and low 70s.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 213 AM CDT Fri Sep 25 2026

The synoptic pattern early this morning is dominated by a
stagnant/blocked upper air pattern with troughing over both the
east and west coasts, with modest ridging over the central
CONUS. A series of upper level shortwaves will eject out the
mean western trough, moving through the central Plains and upper
Midwest over the next 36-48 hours.

Today... Early this morning, one such impulse/PV anomaly will
move across the Corn Belt. The combination of low level theta-E
advection and modest upper ascent /Q-vector convg/ has lead to
the development of widespread showers generally south of US
Highway 20. Rainfall since 7pm /00Z/ last evening has not been
particularly heavy, with most areas picking up less than 0.25".
Portions of west-central IA have seen pockets of heavier
rainfall, with several automated gages and MRMS precip estimates
showing 0.40-0.65." Expect periods of rainfall to continue
through at least mid- afternoon today across the southern 2/3rds
of Iowa. By late afternoon, this batch of forcing/lift will
shift ewd and weaken, with soundings/time-sections showing a
brief period drier air and reduced deep layer saturation, with
showers diminishing for a time. Expect additional rainfall
today in the 0.10 to 0.50" range. Due to the modest rainfall
rates, not expecting any significant hydrologic response except
some minor ponding or within bank rises on rivers. Model plan
view and soundings show very little instability/CAPE today due
to weak, moist adiabatic lapse rates, so nothing more than an
isolated lightning strike expected, and even that maybe
overdone. With abundant cloud cover and precip, expect cool high
temps in the 60s.

Friday night and Saturday...
Another shortwave ejecting out the western trough will induce a
second surge in the LLJ, with a period of enhanced of
WAA/moisture convergence returning Friday night into Saturday.
Scattered to widespread showers will re-develop and move from
west to east across the entire state late Friday night into mid-
morning Saturday, with the heaviest rainfall expected along and
south of US Highway 30, where 0.5" to locally 1" is possible.
On Saturday afternoon, the global and CAM solutions show better
instability /250-1000 J/kg/ is possible across southern Iowa
due to slightly steeper mid-level lapse rates and higher low
level level moisture/Tds. This will likely lead to move
convective elements and thunderstorm activity, which could boost
rainfall rates for a time. This activity will likely continue
into the evening, with another "lull" in the activity Saturday
night as the lift weakens. Depending on the location of the
heaviest QPF axes, additional within bank rises are likely on
area rivers. If higher magnitude QPF solutions verify /90th
percentile/ then a few rivers could approach flood stage. Some
to watch in the upcoming days.


&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 251 PM CDT Thu Sep 24 2026

Dryer air will arrive from west to east late Saturday night
into Sunday though mostly cloudy skies are expected to persist.
Monday will be mostly dry and slightly warmer with highs in the
60s to near 70. Another strong short wave will arrive Tuesday
and Tuesday night. PWAT values will approach 2 inches and
conditions will be favorable for rainfall amounts of 1-2 inches.
Note, Des Moines is currently a little over 2 inches from the
September record for precipitation. This will be approached with
the system this weekend and the one early to mid next week.

For Wed into the end of the week, models are taking turns trying to
ingest the Pacific Hurricane Palo into southwest flow as a strong
upper level low approaches the Four Corners region. There remains a
lot of uncertainty here regarding this ingestion and the overall
evolution of the upper level low but a slower progression of
everything may lead to more wet weather for Iowa.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1054 PM CDT Thu Sep 24 2026

While rain is tapering off in most areas, another wave will be
entering southwest Iowa at the start of the TAF period and will
lift across much of the state through the morning. Highest
confidence to see showers will be KOTM and KDSM, with lowering
probabilities further north given uncertainty in northern
extent, so have used PROB30 and TEMPO groups accordingly. With
this rain will also include lowering ceilings, with increasing
coverage of MVFR/IFR conditions throughout the day. Winds out of
the southeast will increase through the morning, with gusts by
late morning to afternoon up to 15-20 knots.

&&

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

&&

$$

SHORT TERM...Fowle
LONG TERM...Donavon
AVIATION...Bury