textproduct: Des Moines

KEY MESSAGES

- Hot and humid conditions continue today.

- Active period of severe storms and heavy rainfall tonight thorugh Thursday. All severe hazards will be possible through this period.

- Brief break in storm chances Friday with more precipitation returning this weekend.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 313 PM CDT Tue Jun 9 2026

Our hot and moist conditions continue today, as temperatures over the area have already climbed into the upper 80s and low 90s with dewpoints in the low to mid 70s. This has pushed heat indices into the upper 90s to near 100 with additional warming expected before temperatures cool again after sunset. A Heat Advisory remains in effect until 9 pm CDT over western into central and southern Iowa.

A rather active pattern will kick off today lasting through Thursday, as we expect multiple rounds of thunderstorms to occur over the state. The first of these chances begin today into tonight as theta-e advection increases over the state. This warm air will also contribute to an elevated mixed layer, which should help work against thunderstorm development this afternoon. There are a handful of solutions where the boundary layer warms enough to develop storms over Iowa this afternoon, in which case it would have access to a highly unstable environment (2500+ J/kg of mixed layer CAPE) but minimal shear (20 to 30 kts). The instability alone could produce a strong to severe storm, especially as the boundary layer mixes out and DCAPE increases to over 1000 J/kg, with wind and hail the main threats. A brief tornado can't be ruled out if a storm develops, but the threat is low. That said, this would be conditional upon a storm breaking through the cap, which appears unlikely at this time.

Although the likelihood of storms this afternoon is low, chances will be increasing into the evening hours as better synoptic support lifts north and east across western Iowa and a rather robust, 40 to 50 kts low level jet noses up into Iowa. The EML will still be in place, but the better forcing will allow for at least some elevated convection as the wave passes through. This activity is being modeled to stay just northwest of our forecast area, but close enough to warrant watching. The wind shear tonight still won't be great, but the presence of the low level jet and high most unstable CAPE values (3000 to 4000 J/kg) will be sufficient for potentially severe storms, especially over western Iowa where the highest CAPE values reside. Damaging winds and hail will be the main concerns given the elevated nature of storms this evening and overnight. With the LLJ fueling activity overnight, showers and thunderstorms may linger into the early Wednesday morning hours. Instability will be waning by this point, but still high enough (1000 to 2000 J/kg) to produce at least a few strong storms.

Any lingering storms on Wednesday morning should move out by mid- day, allowing for recovery of the atmosphere through Wednesday afternoon. Assuming the atmosphere is able to rebound, the EML will be weaker and lessen the convective inhibition over the area. At the same time, a subtle boundary will drop through the area, providing a genesis region for storms Wednesday afternoon and evening. By mid- to late afternoon, storms are expected to fire ahead of and along this boundary within a highly unstable (3000+ J/kg of MLCAPE) and better sheared environment (35 to 45+ kts) introducing the risk for organized and severe storms. All hazards will be on the table Wednesday afternoon and evening, including damaging winds, large hail, heavy rainfall and tornadoes. The tornado risk seems the most conditional threat for our area, as winds will generally be out of the southeast with marginal SRH (50 to 100 m2/s2), but there is enough low level stretching (0-3km CAPE around 100 J/kg) that a tornado could occur should a supercell develop. The storms Wednesday afternoon will generally be over the south and east, before moving off into eastern Iowa through the morning hours.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 313 PM CDT Tue Jun 9 2026

As we get into Wednesday night and early Thursday morning, another wave will lift northeastward into the state, nosing the LLJ up into the plains and southwest Iowa again overnight. A few short range models (namely the HRRR and RRFS) are producing convection along the nose of the jet overnight, which eventually evolves into an MCS and rides the instability gradient eastward through Iowa. This system could bring strong, damaging winds through the state early Thursday morning. Likewise, very heavy rainfall could occur with the storms that initially develop along the nose of the LLJ before the line moves through and blows the convection out. Depending on where this rain falls, and how long it takes for activity to grow upscale, flash flooding may occur. However, this scenario will depend on how the Wednesday afternoon into the evening convection plays out, and how worked over the environment is over Iowa overnight. Regardless, this MCS and it's trends will be something that needs monitored closely through the next 24 hours.

Trends into Thursday afternoon will depend on the morning MCS and how much the wave pushes through on Thursday. It's possible all the convection is out of our area before the trailing boundary lights up again Thursday afternoon. If the boundary does linger in the area Thursday afternoon, severe weather will be once again possible. However, with so much happening prior to this wave, will continue to monitor through the coming days and see how the models handle each successive wave. A brief reprise from the storms develops Friday but precipitation chances then return again into the middle of the weekend.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 643 PM CDT Tue Jun 9 2026

VFR conditions and southerly winds this evening. A few storms cloud move over far northern Iowa overnight but chances at any TAF sites is low. A gust front from Nebraska storms could arrive after 06z into central Iowa and may bring and increase in wind and a period of more southwest wind flow. The wind will become gusty on Wednesday with gusts over 25 kts. Scattered thunderstorms will be possible over the southeast half of Iowa Wed afternoon. At this time, focused on KALO/KDSM/KOTM with much less confidence at KFOD/KMCW.

HYDROLOGY

Issued at 313 PM CDT Tue Jun 9 2026

Short and longer term hydrologic conditions exist due to active weather over the next few days. Main short term concern is flash flooding potential. Despite widespread amounts of 2-3 inches over the past five days across the southeast half of the CWA with pockets of 4-5+ inches, much of the rain ran off instead of infiltrating because of its intensities/rates. Thus it did not significantly change soil moisture vs. how much rain fell. Compared to normal soil moisture for this time of year, the northwest CWA is the driest, the south central into northeast CWA is slightly above and most other areas are near normal. Although areas with above normal soil moisture are traditionally most susceptible for flash flooding, nearly the entire CWA has the same risk for this event because rainfall intensity/rates over the next few days will likely exceed soil infiltration capabilities in many locations including drier soils, practically speaking. The most likely scenario will be ponding and lower-end flash flooding mainly in towns and cities, however higher than expected rainfall would increase the geographic and magnitude risk.

Longer term, the risk of river flooding over the next several days is minimal (generally less than 15-25%), however minor to moderate within-bank rises are again possible in basins that receive heavier rainfall.

DMX WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 9 PM CDT this evening for IAZ015-023- 033>035-044>048-057>062-070>075-081>086-092>097.