textproduct: Des Moines

KEY MESSAGES

- Widespread shower and storm chances expected on Sunday.

- Increased severe weather and heavy rain chances on Monday. Heavy rain potential continues through mid- week.

SHORT TERM /THROUGH SUNDAY/

Issued at 333 AM CDT Sat Sep 12 2026

As of the latest surface analysis, a cold front and pre-frontal trough are moving across the area. Showers and thunderstorms continue to advance across the DMX CWA early this morning. Based on 0700Z surface observations, the cold front is draped across the far northwestern corner of the CWA and is slowly dropping southeast. Ahead of the front, temperatures remain in the upper 60s to lower 70s with dewpoints in the upper 60s. Behind the front, northwesterly winds are advecting cooler air and dewpoints in the low to mid 50s as weak surface high pressure builds in from the northwest.

Through the remainder of the overnight hours and into the day, showers and isolated thunderstorms will continue to move southeast before dissipating later this morning. A lull in activity is forecast before re-development takes place in southeastern Nebraska as a vort max moves from southeast Nebraska through southern Iowa into northern Missouri. The SPC previously placed the area under a Day 2 Marginal Risk, but with cooler low-level temperatures and a stout cap in place, the strong to severe thunderstorm threat is near zero. However, should a parcel break through the cap, a weak EML could support isolated convection. Otherwise, the remainder of the area should stay dry, with high temperatures ranging from the lower 70s in the northwest to the lower 80s in the southeast, and dewpoints ranging from the upper 40s in the north to the mid to upper 60s in the south.

Beginning late Saturday night into Sunday morning, a surface low is progged to lift north toward the region, bringing increasing chances for showers and thunderstorms throughout the day on Sunday. While the severe weather threat for Sunday has been downgraded to general thunder, increasing moisture advection will drive PW values near the 90th percentile into the area. This abundant moisture, combined with skinny CAPE profiles on forecast soundings, will support efficient heavy rainfall, particularly Sunday night. High temperatures on Sunday will generally range from the mid-60s to the low 70s.

A cold front is bringing showers and thunderstorms to the region this morning, followed by cooler and drier air from the northwest. Severe weather risks remain near zero today due to strong low-level capping, though isolated showers remain possible. By late Saturday night into Sunday, an approaching surface low will increase rain chances, with high atmospheric moisture levels creating the potential for heavy rainfall through Sunday night.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Issued at 249 PM CDT Fri Sep 11 2026

The pattern turns quite active starting Sunday night, as deep layer moisture increases ahead of an approaching 500 mb trough and multiple subsequent waves keep the gulf moisture stream open through the first part of the week. The first day of concern will be Monday as the aforementioned 500 mb trough passes through the northern CONUS. This will bring a push of low level moisture and increasing temperatures up into Iowa, along with strong mid and upper level flow. Instability values in our area will maximized Monday afternoon, with plenty of shear for organized storms. Fortunately, a warm nose aloft will work to keep the atmosphere capped off and activity surface based, at least at this lead time. Still, strong 850 mb winds could certainly support some damaging winds. The storm prediction center has already started to key in on Monday, with a Day 4 15% risk over central Iowa.

The active weather continues through at least Tuesday and Wednesday, although the pattern looks to transition to more of heavy rainfall threat through these next two days. Modeled PWATs around 1.9 to 2" will be conducive for efficient rainfall, and multiple days of convection along a quasi-stationary boundary could lead to some flooding concerns. It's still a bit early to get too ingrained in details, as mesoscale factors could cause this boundary to sink or move around, but the current synoptic setup certainly points towards potential hydrology concerns through next week. The weather prediction center is already on top of this as well, with slight risks for excessive rainfall spanning from Sunday to Tuesday of next week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1219 PM CDT Sat Sep 12 2026

VFR conditions prevail over the state today. Breezy north northwesterly winds with gusts around 15 to 20 kts have developed behind a front that passed through this morning. These breezy winds will persist for a few hours this afternoon, before diminishing into the evening. Light to calm winds are expected overnight. Rain and thunderstorm chances return to the area Sunday morning, primarily impacting KDSM and KOTM, although any terminal could see a shower through the morning. Confidence is lower in the widespread nature of showers, so have only included precipitation mention in TAFs where confidence is best (ie KDSM and KOTM). Occasional thunder is also possible with this activity, but have opted to leave out of TAFs at this lead time.

DMX WATCHES/WARNINGS/ADVISORIES

None.