textproduct: Des Moines

KEY MESSAGES

- Marginal Risk for severe weather in northwest Iowa Sunday, mainly for storms arriving in the evening. Hail is the main threat, damaging winds the secondary (and early window) threat.

- Showers and storms may linger in northern Iowa during the day monday (15-20% chance) then focus in northwest Iowa in the evening.

- Summertime pattern with highs in the 80s for the remainder of the week. Shower and storm chances for the southwest half, mainly occurring in the peak heating hours.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 1229 PM CDT Sat May 23 2026

The front responsible for showers early this morning continued to slowly trek east today. Scattered showers reignited along the convergence and will quickly move east. A few thunderstorms will be possible, but the chances are highest once the line exits the CWA. Cirrus follows behind. Highs will top out in the low to mid 70s this afternoon. A surface high will hold moisture just to the west tonight, and a decaying MCS may bring some light showers in its finals hours of life in northwest Iowa Sunday morning. The moisture axis will start its recovery on Sunday; so will the thermal ridge. Highs in the 80s and dew points in the 60s return and moisture will collect ahead of a surface low in western Nebraska. That feature will succumb to the midlevel height rises overhead, morphing into more of an open wave feature, but it will be enough to kick up the LLJ Sunday night. Warming 700mb temperatures nearing 8C will steepen lapse rates to 8C/km. The LLJ will begin near the Missouri River and storms will extend into southern Minnesota on the instability axis. A Marginal Risk for severe weather covers the hail and wind threat associated with these storms. The LLJ will veer into northern Iowa overnight which supports MCS development Sunday night into early Monday. The lack of shear to balance storms will make them cold pool dominant early, the severe threat lowering as storms enter central Iowa. This thinking is supported by the last few hours of the 12z HRRR.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 1229 PM CDT Sat May 23 2026

Upper-level ridging will start its expansion on Monday in response to the blocking pattern, and the height contours will orient vertically west of here with time, pulling the best moisture axis away from the area. Remnant moisture from the night before will have stalled over northern Iowa, which may be enough to realize the instability that remains before peak heating. Have added in 20% PoPs to reflect this. Better consensus in rain and storms is presented in northwest Iowa in the evening and the LLJ takes over again. Should storms be present in northern Iowa at this point, weak flow will make them assume a slow, perhaps westerly motion.

For the week, Iowa will reside almost under center of the ridge in the omega block, favoring warm, summertime temperatures. The challenge will be the looming moisture axis in southwest Iowa and the trapped closed low ejecting almost due north from the ArkLaTex region. The other challenge is the later arrival of high pressure later this week. Eventually, when that gets here, dry air will dominate. Until we get there, temperatures in the 80s will be accompanied by showers and storms, mainly in peak heating hours. Highest confidence in storms will be across southern and southwest Iowa.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1221 PM CDT Sat May 23 2026

MVFR will hang on at KOTM in the short term. Have timed out VFR conditions as 2030z. Showers have struggled to reappear thus far, and have removed Prob30 groups due to diminishing confidence in impacts from rain. Winds will become variable from west to east tonight and VFR conditions will prevail.

DMX WATCHES/WARNINGS/ADVISORIES

None.