textproduct: Des Moines

KEY MESSAGES

- Warm this week with highs in the 80s.

- There are low chances (20-30%) for showers and thunderstorms nearly every day this week as different systems skim edges of Iowa. It will not be a washout, but a few stray thunderstorms are possible each day, especially later in the week.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 226 PM CDT Mon May 25 2026

Morning showers and thunderstorms cleared out by late morning, making way for a quiet day across Iowa. With dry conditions and deeper mixing across the area south winds have become breezy, gusting 25-30 mph. These breezy conditions will last through sunset until the atmosphere can decouple and limit deeper mixing. Around the same time the low level jet will develop and strengthen, oriented across Kansas and Nebraska, nosed into South Dakota and southern Minnesota. Showers and thunderstorms will develop on the nose of the jet, attempting to take advantage of the waning pool of instability overnight. With around 2000 J/kg of MLCAPE there should be plenty to get storms started, but expect them to be short lived with around 20 kts or less of 0-6 km shear to organize and sustain them. There is some uncertainty as to how long storms will last overnight, skimming northwest Iowa. CAMs seems split at this time with roughly half (NAMnest, ARW, NSSL-WRF) favoring storms dying out overnight while the others (HRRR, RAP, FV3) continue storms across far northern Iowa and southern Minnesota. Given that storms this morning persisted a little longer than expected, it seems that the LLJ should again be able to sustain disorganized and sub-severe thunderstorms through the early morning hours on Tuesday.

The upper air pattern is fairly diffuse with no real feature of note to influence local weather this week. Iowa sits on the edge of a weak surface high, enough to keep the upper air pattern quiet but not quite strong enough to prevent peripheral waves from reaching the area. This means that most day to day weather is more readily influenced by mesoscale features rather than any better developed shortwave or surface low. Tuesday is expected to remain largely dry, though a decaying MCS across Minnesota on Tuesday evening may sink across far northern Iowa by early Wednesday morning. Seasonably warm conditions settle across Iowa on Wednesday with another day in the mid to upper 80s.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 226 PM CDT Mon May 25 2026

The upper air pattern is more pronounced to the west with a level large cut-off upper level low that will be nearly stationary and churn across the west coast most of the week. The west edge of the flow around this trough will align well with the gulf and pump moisture through the central plains. By late week this unstable axis of moisture will shift ever so slightly to the east, beginning to skim parts of southern and western Iowa on Thursday. This may allow for a window of thunderstorm activity into southern and western Iowa from Thursday into the weekend. There is still no robust forcing mechanism so at this time severe storms are unlikely. The main uncertainty is how far this plume of instability will make it and how much of Iowa will (or will not) be impacted.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1042 PM CDT Mon May 25 2026

VFR conditions are forecast through the TAF period and beyond. There are low chances for showers and thunderstorms in northern Iowa overnight into Tuesday morning, with a 30% chance at MCW justifying continuation of a PROB30 group for -SHRA at that site. However, the probability of TSRA is lower (around 20%) and the probability of MVFR or lower visibility is lower yet (around 10%), so those are not advertised in the 06Z TAF. If radar and observational trends increase the probability of those conditions, then an amendment may be needed overnight. Otherwise, light south southwest breezes and only high clouds are forecast for the next 24 hours.

DMX WATCHES/WARNINGS/ADVISORIES

None.