354
FXUS63 KDMX 262354
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
654 PM CDT Sat Sep 26 2026

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Showers and a few storms build back in this evening into the
overnight, with rainfall totals highest in central and southern
Iowa, and localized areas seeing up to 2-4 inches.

- Dry and mild weather by Sunday afternoon and all day Monday
  with highs in the lower 70s.

- High confidence in widespread and repeated rain chances by mid
  next week, with renewed flooding concerns and a few
  thunderstorms.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 258 PM CDT Sat Sep 26 2026

Showers are ongoing across eastern Iowa this afternoon, though some
relatively dry air has been effective at clearing them out. Still,
moisture through the profile will remain high through the rest of
the day. Sounding climatology combined with last night`s 00z
soundings and RAP reanalysis show that PWATs have been near the 90th
percentile and may be approaching record at times for late
September.

Attention shifts to the next shortwave/weak remnant MCV and moisture
plume advecting towards our region out of eastern Kansas. Mid-level
flow is relatively weak with this system, but the shortwave is
expected to meander across the state this evening into the
overnight. This places the 850mb trough across eastern Nebraska and
resurges the LLJ over central Iowa tonight, though the "nose" isn`t
expected to be all that pronounced and may not provide much forcing.
PWATs up to 1.7" are being observed in the Kansas moisture plume and
would bring efficient rainfall with any showers/storms that form
tonight. Temp profiles tonight will be nearly moist adiabatic and
minimize any sort of severe weather threat, though a plume of weak
MUCAPE (~500 J/kg) may exist across NW Iowa tonight and may support
some thunderstorms. Forecast rainfall totals across the 12z model
suite are notably lower now, with many areas receiving minimal
rainfall tonight, though CAMs are beginning to suggest two specific
regimes of concern. Area one is near the IA/MO border where the MCV
may slow tonight and bring long-duration rainfall to a small area.
Some CAMs suggest localized rainfall as high as 2-3 inches, but
flash flood concern is not all that high considering the way this
may be spread across 4+ hours and soil moisture is near average in
this area. It is also worth noting that this feature has so far been
unable to drum up very noteworthy rainfall totals in Kansas. The
other possible area of concern is further north, where MUCAPE may be
a bit higher, and scattered slow-moving showers and storms are more
likely rather than continuous showers in the south. Still, recent
CAMs are not suggesting high coverage or training of these storms.

Showers may linger into Sunday morning, but overall dry air
advection is expected with the brief return of high pressure from
the Great Lakes. Drier air in this case means the midlevels hang
around 80% humidity rather than 100%, so clouds may stick around for
a good part of the day on Sunday. However, high pressure and mild
conditions hang around through the day Monday as well. 850mb Tds may
still be around 10-11C but the mid and upper levels really start to
dry out Monday morning, resulting in more clearing of clouds and
highs temps returning to the 70s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 258 PM CDT Sat Sep 26 2026

The dry weather is short lived, as Tuesday looks like the first of
several more rainy days with renewed flooding potential. By Tuesday,
the western trough is cutoff from the main flow and slowly makes its
way towards Iowa, leaving the area sitting beneath several days of
southwest flow. Particularly on Tuesday and Wednesday and perhaps
Thursday, a slow moving surface boundary looks to set up SW to NE
over Iowa with repeated flare ups of the LLJ and a persistent
moisture plume with PWATs of 1.5-2". The wild card in all this is
the behavior of Hurricane Polo, whose remnants at mid levels may
make it past the Sierra Madre mountains in Mexico and help to
enhance the gulf moisture transport ahead of the cutoff low. The
result is high confidence in repeated rounds of heavy rainfall and a
few thunderstorms mid week. WPC QPF guidance shows widespread 48hr
totals near 2-4", and the threat for localized higher totals due to
training thunderstorms is definitely present. Given already high
soil moisture content, expected totals will be enough to bring up
flash flood and river flood threats. Experimental HEFS guidance has
a 50% chance that many central and southern Iowa rivers and streams
reach or exceed action stage and border on minor flood stage next
week, and a 30% chance that some (Raccoon/Skunk/Thompson) reach
minor to moderate. With so many moving pieces on the synoptic and
mesoscale, trends will need to be monitored and changes are
expected.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 655 PM CDT Sat Sep 26 2026

MVFR ceilings continue to impact KFOD and will decrease to IFR
ceilings with chances of fog through the overnight period. IFR
ceilings will eventually reach KALO/KDSM overnight as well.
Showers are moving through the area impacting KDSM at this time
before continuing east to KOTM/KMCW/KALO in the next couple of
hours. Showers may linger through the night with gradually
decreasing chances into early morning. MVFR/IFR ceilings will
persist at the western and northern TAF sites through the late
morning into early afternoon.


&&

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

&&

$$

SHORT TERM...De Bruin
LONG TERM...De Bruin
AVIATION...Wyss