textproduct: Des Moines

KEY MESSAGES

- Breezy with scattered, intermittent showers through this afternoon. If new activity can develop, a few thunderstorms are also possible in mainly western and southern Iowa this evening. More widespread storms move through overnight. A few gusty winds are possible overnight, but severe weather is not forecast.

- Locally heavy rainfall and isolated flash flooding are possible into tonight over southern Iowa and northern Missouri.

- Conditional threat for strong to severe storms on Sunday, in mainly western Iowa, though potential is low at this time.

SHORT TERM /THROUGH MONDAY/

Issued at 239 PM CDT Sat May 30 2026

Upper level pattern continues to feature an Omega block but both the eastern and western upper lows undergo some amount of northerly movement over the next few days. This still largely keeps upper riding over the central U.S. but a lee side surface low will develop and move northward into the Dakotas into Sunday. Have continued to see showers lift northward into early this afternoon after they developed this morning with additional activity developing in especially portions of north central into eastern Iowa along the theta-e gradient. Shear continues to be weak with the main area of instability in southwest Iowa so largely expecting any of this developing activity to be mainly showers with the only hazard lightning for the most part, which given where the main instability axis is and these showers are developing, is on the lower side too. However, as noted in the previous discussion, the non-supercell tornado parameter is picking up on an area in mainly western Iowa where around 100 J/kg of 0-3 CAPE overlaps with surface vorticity which could potentially lead to the development of a few funnel clouds though again shear is quite weak and there is no notable boundary. Will continue to monitor this closely through the rest of the afternoon hours.

As we get into tonight, there continues to be disagreement between the CAMs and global models on new showers/storms that can develop ahead of an expected approaching MCS which looks to reach far southwest Iowa around 06Z. Although cannot rule out a few gusty winds in far west/southwest Iowa as this MCS arrives, it will encounter a more stable environment so the expectation is the line of storms will weaken as they cross and move through Iowa overnight. However, as also noted in the previous discussion, it may be able to maintain a heavy rain threat with pwat values between 1.5 to 2" in southern Iowa and favorable warm cloud depths. Several guidance sources continue to suggest an area of 1-2" with an even more highly localized area of 2-4". With the overnight activity, these highest rain totals look to be in northern Missouri with the slightly lighter amounts into southern Iowa. Prior to that, centered around this evening, the NAMNest, HRW NSSL and to a lesser degree ARW all kick off exceptional rain totals with any storms that can develop in southern to southwest Iowa prior to the MCS. Will agree that anything that can develop ahead of the MCS would still be in an environment for efficient rainfall and would be slow moving, what remains more unclear if there is enough forcing to kick off these new showers/storms (other than the areas already discussed above). With this uncertainty, confidence was not high enough to issue a flood watch though areas in especially Taylor and Ringgold Counties are especially primed given heavy rainfall a couple weeks ago and in Taylor County, this morning. WPC maintained the Marginal Risk (Level 1 of 4) for Excessive Rainfall given the possibility for heavy rain and localized flash flooding to occur which was supported locally and with neighboring offices given the environment but uncertainty in storm development and coverage. Will continue to monitor the hydro threat into this evening as well.

Behind the departing MCS on Sunday, the mesoscale details remain more uncertain with additional storm development. SPC maintained the Marginal Risk (Level 1 of 5) for severe weather over the southwest half of the state but removed the Slight (Level 2 of 5) in western Iowa with the overall setup conditional. If storms can develop, large hail and strong winds could be possible in a strong to severe storm, as well as additional heavy rain, with weak, but overall better shear than today and plenty of instability. However, soundings looked capped with midlevel dry air through a good portion of the day and there isn't a discernible mechanism to kick off new activity either thus reliant on any features left from the MCS overnight.

It will be warm and muggy in the 70s to 80s with dew points in the 50s to 60s through Sunday.

LONG TERM /MONDAY NIGHT 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 /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1055 PM CDT Sat May 30 2026

A line so scattered showers and thunderstorms has reached far southwest Iowa and will spread across the state overnight, lingering through Sunday morning. This is expected to weaken as it moves into central Iowa, though thunderstorms are still possible. Have included prevailing mentions at KFOD/KDSM/KOTM on the mostly likely window for showers with a prob30 group to time out the thunder chances. Introduced prob30 -shra groups at KMCW/KALO as data has trended towards showers reaching farther east on Sunday. There is uncertainty as to how long the scattered activity will linger into Sunday and adjustments are likely. Additional thunderstorms are possible SUnday night just beyond the current TAF period.

DMX WATCHES/WARNINGS/ADVISORIES

None.