textproduct: Des Moines

KEY MESSAGES

- Drier conditions today through the day Wednesday. Highs around 80 degrees or in the low 80s with breezy winds over western Iowa.

- Pattern turns more active starting Wednesday night and Thursday with multiple rounds of rain and thunderstorms possible into this weekend.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 155 AM CDT Tue Jun 2 2026

Early morning GOES-East upper level water vapor imagery shows an active scene over the central Plains and down into the Deep South with ongoing convection. Of most interest to our forecast are the storms over Nebraska, which have shown a trend downward per cloud top temperatures and lightning activity. SPC mesoanalysis shows weaker MUCAPE and effective shear as these storms move towards the Iowa border this morning. Thus, it is not surprising that convective allowing models (CAMs) and global models are in good agreement that these storms will fizzle out before reaching our forecast area if not the state. While the environment is not conducive to maintaining severe storms as outlined above, a sprawling zone of surface high pressure is sinking into and over the Great Lakes today, which is directing drier air into the state. A few models such as the GFS, Canadian, and RRFS (MPAS core) try to paint light QPF over our far western forecast area from the remnants of the Nebraska storms or some sort of outflow generated activity. This is in line with the eastern extent of the latest day 1 SPC general thunder outlook; however, given the amount of dry air shown in soundings and subsidence from the high along with the rest of guidance pointing to dry conditions, am planning to carry a dry forecast today. Otherwise, today will be seasonably warm with highs a few degrees either side of 80 degrees, dewpoints falling back into the 50s western and central to 40s eastern Iowa, and breezy winds with ample sunshine.

The upper level omega blocking pattern will be starting to break down on Wednesday while the surface high pressure shifts from the Ohio Valley into the Middle Atlantic States. This will offer another day of dry conditions for central Iowa with highs just a bit higher in the low 80s with a bit more cloud cover than today/Tuesday with breezy winds once again over western Iowa. As the high pressure does move away from the region, the plume of higher precipitable water values that will be west of Iowa will begin to drift closer, which is discussed in more detail below.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 250 PM CDT Mon Jun 1 2026

Wednesday night and through the second half of the week will see a slight change in the pattern, as the eastern US long-wave trough departs eastward and the surface high follows along with it. Return flow on the backside of the departing high will advect warm moist air up into the state, meeting with another shortwave trough along the US/Canada border Wednesday night into Thursday. This will bring the return of shower and thunderstorm chances to Iowa, mainly over northwest into northern Iowa, although rain could develop throughout the area as theta-e advection increases ahead of the wave. This Wednesday night into Thursday rain will kick off a more active pattern through the end of the week, as we transition to more of a zonal flow pattern with multiple shortwave passages into the weekend. Instability will also be increasing through the end of the week, as the warmer and higher dewpoint air works up into the state. It's a bit too early to dig too far into the severe weather potential, but Friday looks like it has the greatest potential for a few strong storms, albeit limited by low wind shear values. Machine learning probabilities are keying on Friday as well, putting a 5 to 15% probability for severe storms (equivalent to a marginal risk from SPC) on Friday. Of similar concern will be the potential for multiple days of rainfall Wednesday night through Saturday, some of which could be rather efficient as the better moisture stream and PWATs pivot westward into Iowa. This could be some much needed rainfall, provided it doesn't all fall in one spot. Potential severe weather and hydro concerns will continue to be evaluated in the coming days. Warm, summer-like conditions persist through the weekend and into early next week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1055 PM CDT Mon Jun 1 2026

VFR conditions ongoing and expected to continue through the TAF period. Light winds out of the east to southeast are expected overnight and only pick up slightly towards 10-12 knots Tuesday. Clouds from Nebraska will try to move towards western and central TAF sites but will be fighting dry air. Opted for high clouds but if lower clouds (FL050-080) can make it further east, may need additions at KFOD and maybe KDSM.

DMX WATCHES/WARNINGS/ADVISORIES

None.