textproduct: Des Moines

KEY MESSAGES

- Slow moving, efficient rainfall storms with isolated heavy rainfall this morning diminishing toward midday, then a dry interval through this afternoon.

- There is a chance of a few severe storms this evening into tonight, but the question is if storms can develop. If storms do develop, gusty winds, hail, and locally heavy rainfall will be the main threats.

- Monday is favoring drier conditions with capping in place to limit if not prevent storms. However, similar to Sunday, if storms can develop, a few severe storms with large hail or gusty winds are possible.

- High pressure drifts southward through the Great Lakes into the Ohio Valley, which pushes rain and storm chances west of the state Tuesday and Wednesday and perhaps Thursday. Highs above normal in the 80s.

SHORT TERM /THROUGH TONIGHT/

Issued at 150 AM CDT Sun May 31 2026

Early morning radar imagery has shown convection blossoming over southwestern Iowa into our southwestern forecast area, which is within a broad area of 850mb low level warm air advection. These storms are moving ever so slowly to the north around 10 to perhaps 15 mph. The 0z KOAX RAOB measured precipitable water (PWAT) values at 1.51", which is between the 90th percentile and the daily max. So, there is an impressive reservoir of atmospheric moisture where these storms have developed with relatively drier air sitting over eastern Iowa with the 0z KDVN RAOB just under an inch and closer to the median PWAT value. An earlier line of convection, which early in the day (May 30) convective allowing models (CAMs) showed pushing through, has now fizzled while a stronger area of convection is ongoing over eastern Kansas pushing into Missouri. CAMs show the activity over southwestern Iowa generally moving to the east and northeast through the forecast area and losing intensity as it does so. There may be credence to this idea given the upper level pattern that has a lobe of shortwave energy (associated with the left/upstream part of the omega block) lifting northeastward over the central Rockies while in the low levels the jet focuses more over Kansas. While there is no severe weather threat with this activity due to the weak effective shear, locally heavy rainfall will remain possible in this favorable environment. Unlike this time yesterday, CAMs and the HREF and REFS have gone full retreat on the higher magnitude rainfall amounts previously discussed last night. Isolated totals by midday today could near 2 to 3 inches (RRFS (both cores)/REFS) to 1 to 1.5 inches in most other CAMs and the HREF. Thus, the concern for flash flooding is quite a bit lower than this time yesterday.

Any lingering convection should be lifting northeast of our forecast area by early this afternoon. This will be pulling the mid and high level clouds away from the area, though there looks to be plenty of lingering low level moisture per RAP cross sections so the amount of sunshine looks to be limited at this point. So, it does look like a dry period from sometime this morning for some to many by this afternoon. With warm level aloft capping the atmosphere and the cloud cover, it remains to be seen how much storm development could occur this evening given the weak low level thermal lift and QG convergence. Models differ on where the LLJ may be pointing with some towards southwest Iowa while others veer into central Missouri. If isolated to scattered storms are able to develop, the environment features between 2000 and 3000 J/kg per forecast soundings and plan view models. However, deep layer shear looks to be marginal between 20 to 30 knots (RAP) to at best 30 to 35 knots (GFS). Soundings persist good saturation in the lowest 1km while the mid-levels dry out yielding favorable downdraft CAPE values for gusty winds to be possible. Thus, any severe risk looks contingent on 1) storms developing and 2) there being sufficient shear to sustain convection. Heavy rainfall parameters will still be favorable with PWATs above normal and between 1.25 and 1.5 inches and deep warm cloud depths. Storm motions will be faster though around 20 to 25 mph with storms pushing generally to the east or perhaps southeast. Again, if storms are able to develop, isolated rain totals from any Sunday night storms could be between 2 to 3 inches on the upper end by Monday morning. However, most are unlikely to see these amounts with some places perhaps seeing no rainfall.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 239 PM CDT Sat May 30 2026

Upper ridging is maintained to start the new work week with moisture largely shunted to the south and west until closer to midweek when shower and storm chances again return to the forecast. Details at this time range remain uncertain with a surface high over the Great Lakes to contend with. Temperatures remain in the 80s through the week.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 623 AM CDT Sun May 31 2026

Scattered showers and a few storms are passing through Central Iowa this morning. Confidence is medium that these showers will continue at terminal sites for a few more hours. To represent the showers, prob30s have been introduced at FOD,OTM and DSM. This could lead to flight restrictions. Though prob30 is not at ALO or MCW due to lower confidence, a passing shower can't be entirely ruled out this morning. As we head into tonight, additional showers or storms will be possible but confidence is too low to issue prob30 at any given terminal site. Winds will turn light and variable tonight which could lead to areas of patchy fog near the end of this TAF period at FOD and DSM.

DMX WATCHES/WARNINGS/ADVISORIES

None.