textproduct: Des Moines

KEY MESSAGES

- Elevated fire weather conditions in the northwest today. A low chance (20%) for showers in the north.

- Expansion of the Slight Risk for severe weather Thursday, now including the entire area. Damaging winds and isolated tornadoes are the main threats, large hail secondary. Severe weather will extend into the nocturnal hours.

- Next window for storms Sunday night into Monday.

SHORT TERM /THROUGH THURSDAY/

Issued at 349 AM CDT Wed Apr 22 2026

A moisture discontinuity was observed tonight both with surface obs and in differences in GOES Nighttime Microphysics. The leading edge of theta-e advection was illustrated by the forming midlevel clouds in western Iowa. There is also CAPe associated with this moisture axis, totaling around 500 J/kg. Have added low chance PoPs in the northwest today as saturated parcels look to take advantage of the elevated convective environment. Rainfall production will be high enough that some drops will overcome the dry low-levels and reach the surface. Dew points in the 50s will follow the boundary, building into the area through the afternoon. The building EML aloft won't be as conducive for mixing like seen yesterday, so highs will be closer to NBM guidance and in the low 80s. The driest air mass will be over northwest Iowa where moisture advection is less of a factor today. This is where temperatures have a better chance of overperforming and where fire weather conditions are elevated today. The LLJ will increase in western Iowa and keep surface winds elevated tonight.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/

Issued at 349 AM CDT Wed Apr 22 2026

The most notable change to the forecast period is the expansion of the Slight Risk area for Thursday, now covering all of the DMX CWA. This is in response to an improved wind field over the region. Recall yesterday that it appeared mid and upper jet influences were going to be too far west, decreasing the LLJ and confining shear into the lowest 3km. That is less the case today, as the dynamics now look to align more favorably, this is due to a secondary vort max ejecting around the base of the parent trough around 00z, enhancing the mid and low level jet over Iowa. Pre-frontal convection on the instability gradient, possibly presenting itself as an MCS in the morning, brings some questions of NSE recovery, but if the cold front arrives later, the warm sector has added time to destabilize. Soundings at this range favor a moist PBL with some scattered convection possible through the day (some hail included), favoring low LCLs. The moisture and the elevated winds in the PBL will delay decoupling and keep surface-based potential going into the overnight hours. The HRRR may be decoupling too fast and favoring a cold pool dominant line prematurely for this reason. 0- 3km shear is over 35kts and points northeast, giving the QLCS cold pool balance and a tornado threat into the nocturnal hours. The increased 850mb wind field supports the tornado threat with SRHs between 150 and 200 m2/s2 in the lowest kilometer. Not to be forgotten is the wind threat due to theta e differences of 12K and the aforementioned increased wind field in the NSE.

The cold front shoves moisture away for a few days and troughing to the north will keep temperatures in the 60s to start the weekend. Western CONUS troughing starts to amplify Saturday and causes cyclogenesis off the Lee Rockies in Colorado. This feature will eject northeast while the trough tilts negatively. It appears the surface warm front will make it as far north as southern Iowa and could spell strong to severe storms Sunday night into Monday.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1037 PM CDT Tue Apr 21 2026

Little change from previous forecast with the wind becoming light and variable at times north with KDSM/KOTM maintaining a southwest wind overnight. The wind will become more southerly on Wednesday and will be breezy. Still monitoring MVFR stratus over southeast Kansas. There remains uncertainty on impacts reaching KDSM/KOTM. At this time, confidence remains low enough to exclude. A few showers could develop over northern Iowa on Wednesday though cloud bases will remain 9 kft or higher.

DMX WATCHES/WARNINGS/ADVISORIES

None.