textproduct: Des Moines

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.