textproduct: Des Moines

KEY MESSAGES

- Multiple rounds of severe storms and heavy rainfall expected tonight through Thursday. All severe hazards are expected, including damaging winds (potentially up to 80 mph early Thu), large hail, and tornadoes.

- Cooler, drier conditions develop on Friday

- Thunderstorm chances return Saturday, some of which may be severe.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 301 PM CDT Wed Jun 10 2026

The next 36 to 48 hours are going to see multiple rounds of severe storms and heavy rainfall. To simplify the discussion and break up the wall of text, we will be breaking it up into the 3 different rounds of storms.

>> Round 0: Earlier This Morning (Wed AM)

Storms from this morning into mid-day today (we'll call them Round 0) produced rather healthy wind gusts of 50 to 60 mph as they moved through north central into northeastern Iowa, with a few personal weather stations reporting gusts just shy of 70 mph. Tree damage and power outages were relayed from multiple towns impacted by the round 0 storms. These storms have since departed the area, allowing the environment to start its path to recovery this afternoon.

>> Round 1: This Afternoon and Evening (Wed PM)

We now look ahead to our next round of storms expected to develop over central into southern Iowa now through this evening. Cloud cover from this morning's activity has begun to clear out from east to west, allowing temperatures to warm over western into central Iowa. Agitated cumulus over these areas, as well as model soundings, suggest the elevated mixed layer is still keeping things mostly capped off as of this writing. However, this warm nose is forecast to cool quickly as surface temperatures warm this afternoon, which will allow for convection to initiate ahead of and along a boundary passing from west to east through the area. Discrete supercells will be favored initially, thanks to the large amounts of surface based CAPE (4000+ J/kg) and 0 to 6 km shear values of 40 to 50 kts. These storms will be capable of all severe hazards, including damaging wind gusts, large hail, and tornadoes. The tornado threat will be highest along the southern Iowa border, where winds will be more south to potentially south southeasterly with 80 to 100 m2/s2 of 0- 1km SRH. The tornado threat will be lower farther north where low level winds will be less favorable for tornadogenesis, but an isolated tornado still can't be ruled out with any supercells, especially with strong low level stretching along the boundary (0- 3km CAPE of 150 to 200 J/kg). Large hail (2"+) will also be in play given the potential for fairly large, rotating updrafts. Of course, strong updrafts produce strong downdrafts, especially in a 900 to 1000 J/kg downdraft CAPE environment, leading to strong winds.

The east northeast storm motions along and ahead of the southwest to northeast oriented boundary will eventually lead to competing updrafts and likely a congealing of storms. This may favor a more linear mode or a line of embedded supercells. It will also lead to some training of storms and prolonged periods of heavy rainfall over southern Iowa. Some model guidance is kicking out QPF amounts of 2 to 4 inches with isolated amounts nearing 6+ inches along the Iowa/Missouri border. Should this occur, it would undoubtedly lead to some hydro/flash flooding concerns, especially if it lines up with any towns or urban areas. For this reason, have decided to issue a Flood Watch for this area through the afternoon and evening. For more information, see the hydro discussion below.

Storms this afternoon and evening over central and southern Iowa will eventually track south and east through the evening, departing the area by around 11pm.

>> Round 2: Late Tonight into Early Thursday (Thu AM)

After the afternoon and evening storms move out, we will have a brief lull through midnight. However, a second wave forming over Kansas will lift northward through Thursday morning, nosing a 45 to 55 kt low level jet into eastern Nebraska and western Iowa. The storms from the first round will have shunted the boundary and instability gradient southward, giving them a more east to west orientation. As the LLJ/shortwave intersect with this boundary, storms will begin to develop along it. The exact track of these overnight storms has been shaky among guidance, as it will depend on how mesoscale features look after storms move through this evening. That said, the expected region for the overnight storms is generally along the I-80 corridor, although this will be subject to change following round 1.

Regardless of where storms end up being, the expected progression is for storms to initially form along the nose of the LLJ in a west to east orientation. These storms will initially train behind each other, given the easterly storm motions expected, leading to a potential hydro threat through central Iowa. Soils are fairly dry in these regions, so flash flooding will be mainly confined to urban areas. See the hydro discussion below for more details. With the highly unstable environment along the boundary (3000+ J/kg of MUCAPE and 40 to 50 kts of 0 to 6 km shear), supercells could develop initially making damaging winds, hail and tornadoes all a possibility over western Iowa. However, models suggest storms will quickly evolve and grow upscale into an MCS as they progress eastward through Iowa along the instability gradient. This will pose a risk for damaging winds up to 80 mph and potentially a few mesovortexes/embedded tornadoes along the line, especially as we get closer to sunrise on Thursday. This line of storms is expected along the I-80 corridor from roughly 4 am to 11 am, including the Des Moines metro area. Additional storms and stratiform precipitation may linger longer over northern Iowa into mid-day, but the most impactful conditions are expected with this leading line of storms.

>> Round 3: Thursday afternoon into the Evening (Thu PM)

The wave responsible for the storms late tonight into early Thursday morning will track eastward over the state during the day Thursday, likely keeping rain over the area in some capacity throughout the day, especially north. The trailing cold front from this wave is then expected to develop more storms in the afternoon and evening over central into eastern Iowa, although the severity of these storms is a bit uncertain for our area. The round 2 storms are trending a bit later into the morning on Thursday, which may limit the amount of time the atmosphere has to recover on Thursday afternoon. This is especially true if showers and storms linger behind the morning MCS. That said, models still suggest that some clearing will develop over southern Iowa, allowing for mixed-layer instability values to climb back to around 3000+ J/kg Thursday afternoon. The shear won't be as strong (30 to 40 kts ahead of the front), but still conducive for organized storms and severe weather. With surface based storms expected, all severe hazards will be possible over central into eastern Iowa tomorrow afternoon, including damaging winds, hail and tornadoes. That said, the tornado threat will likely be best nearer to the triple point in northern to northeastern Iowa where the more southeasterly winds meet the better low level instability/stretching. Again, this will all be contingent on how rounds 1 and 2 play out, and very well could end up being mostly east of our forecast area.

Of note, behind the wave and cold front, models are producing quite gusty winds as dry and cooler air fills in behind the low Thursday afternoon and evening. Wind gusts of 30 to 40 mph look possible behind this front.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 301 PM CDT Wed Jun 10 2026

Behind the cold front on Thursday, conditions become cooler and drier through Friday. Thunderstorm chances then return again on Saturday, with severe storms possible once again Saturday afternoon. With so much ongoing in the short-term, will discuss this risk more thoroughly once we are through the current active period.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1234 PM CDT Wed Jun 10 2026

Breezy to gusty SSW winds will continue through much of the day, with wind gusts dropping out after midnight. Several rounds of thunderstorms are expected through the TAF period, with the first beginning as early as 18z impacting most northern sites and has been reflected in a TEMPO. The second round of thunderstorms is expected to begin around 00z. Confidence in coverage of this round is lower and thunder mentions have been left as PROB30. KOTM is the most likely site to be impacted by this round, but ongoing thunderstorm development makes it difficult to time out when thunderstorms will be over the terminal. Have left showers as prevailing and PROB30 for thunder as a result. The final round is expected to begin around 12z Thursday, with more widespread coverage. Thunder mentions were PROB30'ed again here and timing will be refined in later issuances.

HYDROLOGY

Issued at 1134 AM CDT Wed Jun 10 2026

Flash flood concerns exist through Thursday morning due to rainfall earlier today as well as additional rain later today into tonight. See the latest WPC Day1/Day2 Excessive Rainfall Outlooks (EROs) and Mesoscale Precipitation Discussions (MPDs), as well as NWC Flood Hazard Outlooks (FHOs) and Area Hydrologic Discussions (AHDs) for more details. We issued a flash flood watch up to I-80 to highlight the threat through Thursday morning.

Greatest concern is potential flash flooding tonight in central and southern Iowa. Training storms may produce up to 3-4+ inches of rain in those areas. Flash flood threat in central Iowa would mainly involve urban areas including the Des Moines metro area. Higher end rainfall may lead to flooding of creeks and small streams. In southern Iowa, flash flood concerns involve more than urban areas, such as roads going through lower areas or near streams. Higher end rainfall there may lead to more significant flash flooding.

With much of the potential flash flooding occurring during the night, floodwaters can be more difficult to see especially in areas that lack urban lighting. We would like to remind people to avoid driving into flooded areas, instead find an alternate route. Also people living in areas prone to flash flood impacts should plan in advance what to do if floodwaters threaten their areas tonight.

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

Flood Watch from late tonight through Thursday morning for IAZ057>060-070>072-081-082-092. Flood Watch through Thursday morning for IAZ061-062-073>075- 083>086-093>097.