textproduct: Des Moines

KEY MESSAGES

- Multiple low (<20%) storm chances through tonight. A Marginal (Level 1 of 5) Risk for severe weather is in place for northwestern Iowa where storms have the potential to be strongest.

- A cold front will clear the area by Wednesday morning, leading to dry conditions through the rest of the workweek.

- The next disturbance will move through this weekend, followed by a pattern change next week.

SHORT TERM /THROUGH TONIGHT/

Issued at 142 AM CDT Tue Aug 25 2026

Evidence of capping showed its hand tonight in the form of stratus, located at around 6kft, or 800mb, which lines up well with where models initialized tonight. Upstream of the state was a messy complex of thunderstorms near ABR. Cold pool propagation vectors favor these storms to sink southeast towards Iowa, landing near the state line at sunrise. They'll weaken with time with thunderstorm activity waning by the time they outrun instability.

The remnant cold pool of a phantom MCS was sinking south into Nebraska and looks to serve as a secondary anchor point for storms tonight. If Nebraska storms become active tonight, it will have negative consequences on available instability for our storm potential later today. Delving into a worse case scenario: MLCAPE values over 1500 J/kg encroach from the west this afternoon, following along a pressure trough that will be in northwest Iowa by around 20z. At the same time, a midlevel jet max will enhance deep- layer shear in southern Minnesota and northern Iowa and line up orthogonally to the pressure trough/boundary. That said, convergence along this boundary is poor; warm sector winds are out of the southwest and cool sector winds are from the WSW, at best. Overcoming CIN will be difficult with these weak kinematics, as displayed by most models struggling to simulate convection in Iowa this afternoon. The GFS precipitation can be considered an outlier as its overmixed highs in the mid 90s simulate cap erosion. Better chances for convection are with the better kinematics in Minnesota and Wisconsin, which geographically lie closer to the synoptic low. Chances in Iowa this afternoon remain under 20%. If trends continue, the Marginal Risk for severe weather may be trimmed in later updates.

Slightly better moisture continuity comes together across southern Iowa tonight, which may prompt elevated non-severe thunderstorms before sunrise. Most of the moisture will be in the midlevels as the LLJ won't reach Iowa. Chances again remain under 20% as kinematics remain poor.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 225 PM CDT Mon Aug 24 2026

Conditions are expected to remain unchanged as Iowa stays in a pattern of northwest flow. The next disturbance moves through sometime Friday evening into Saturday morning. Beyond that the pattern looks to change as the high that has been pancaked over the Four Corners region begins to break down, leading to a return of warmer temperatures.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 631 AM CDT Tue Aug 25 2026

Showers in southern Minnesota have continued to decay early this morning, so left out of KMCW. If there is precipitation in the next 6 hours, it will be of low impact. Near-MVFR stratus has been expanding in western and central Iowa and will most likely cover KFOD, KDSM, and KOTM in the short term. Added in TEMPO groups for when cigs may drop to 27-30kft as seen in observations. Stratus will become SCT in the afternoon.

Have withheld from precipitation mentions in the afternoon hours as storm chances have now dropped under 10%. The severe weather chances have also decreased. KOTM has a secondary window of precipitation after 06z, but have not mentioned at this time as chances are below 20%.

A wind shift will move from north to south. Southeast winds will become southerly by midday, then westerlies and northwesterlies will gradually transition in after 00z.

DMX WATCHES/WARNINGS/ADVISORIES

None.