textproduct: Des Moines

KEY MESSAGES

- Warmest temperatures of the week expected across Iowa today, as highs climb into the upper 80s to near 90.

- An isolated shower/storm is possible (10-20% chance) over northern Iowa late this afternoon or early evening. No severe weather is expected.

- Temperatures remain in the 80s through the remainder of the week and weekend. Conditions will be mostly dry, but occasional showers or storms could occur at times, mainly over western Iowa.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 300 AM CDT Wed May 27 2026

We once again start this morning's discussion with scattered showers and occasional thunder over northern Iowa, although this activity has waned considerably just in the time it took to write this. An outflow boundary propagating southward had tried to kick off additional storms just after midnight over north central Iowa, but it has since outrun the unstable air over northern Iowa and now wanders aimlessly into central Iowa. Through the morning hours, the expectation is for rain and occasional thunder to continue to diminish, although cant rule out at least a rogue shower lingering to around day break. Regardless, the potential for any severe weather the rest of this morning is low.

Skies clear out nicely again today, giving way to sunshine and what looks like will be the warmest day of the week. Highs will approach the upper 80s over much of the area, with a few locations reaching or exceeding 90F. NBM seems to have a fairly good handle on the spread in high temperatures today, with only a 2 to 4 degree spread between the 25th and 75th percentile temperatures at most locations. Our relatively static pattern can be thanked for this tight spread in solutions, as Iowa remains under a broad area of upper level ridging, sandwiched between a western CONUS cutoff low and northeastern CONUS trough. At the surface, this has kept us in weak high pressure with light winds, mostly dry conditions and ample sun.

A well-mixed boundary layer today will once again produce some instability primarily over the northern half of Iowa this afternoon and evening, introducing potential for isolated showers or storms. That said, with minimal moisture transport to replenish the atmosphere from rain last night into this morning, storms will have to squeeze what little moisture is left out of the existing environment. This lack of available moisture has kept precipitation coverage fairly minimal in model guidance, and the forecast reflects this with just a few hours of low shower/storm chances (< 20%) through the peak heating hours. If a storm does develop, MLCAPE will generally be around 1000 to 2000 J/kg (depending on the model) but with almost no deep layer wind shear. A stronger storm could produce some small hail and/or gusty winds as it precipitates into the dry air below, but the severe risk is low.

As we go through Wednesday night and into Thursday, our persistent surface pattern from the last few days will begin to undergo a slight change. Surface high pressure will begin to build over the Great Lakes region and it's influences will begin to spill into Iowa. Temperatures will begin along a subtle cooling trend, as east southeasterly low level flow begins to push the the thermal ridge back west and milder temperatures advect in. That said, the net result will only be a couple degree change in temperatures, with highs still reaching the mid 80s on Thursday then low to mid 80s through the remainder of the week. The building Great Lakes high will also keep drier air over Iowa, with the main moisture stream staying off to our south and west through at least Thursday. There is some potential for light precipitation to leak into the southwest portions of the state as the moisture stream oscillates eastward late Thursday into early Friday but overall the chance for showers or storms looks low with the surface high pressure overhead.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 210 PM CDT Tue May 26 2026

The upper air pattern is largely unchanged into the weekend with a plume of instability from the Gulf and through the plains, skimming western Iowa. This will provide a window for diurnal thunderstorm development each afternoon and evening along this axis through Friday and the weekend. Sunday and especially into Monday the surface high east of the area builds back, helping to push thunderstorm chances west of the area and keeping Iowa dry. At this time guidance suggests that this will remain in place through early next week.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 1124 AM CDT Wed May 27 2026

VFR conditions will prevail at all terminals through the period. Light and variable winds will persist today and tonight. Tomorrow morning, winds will take on a more easterly direction at around 10kts. There is a low chance (10-15%) for a shower or thunderstorm to impact KFOD or KMCW this afternoon. Due to low confidence and low probability, this was not mentioned in the TAFs but will be monitored for the 00z issuance.

DMX WATCHES/WARNINGS/ADVISORIES

None.