textproduct: Des Moines

KEY MESSAGES

- A prolonged period of hot, muggy, oppressive weather will begin Sunday and will likely continue through the coming week and potentially the Fourth of July weekend. An Extreme Heat Watch has been upgraded to an Extreme Heat Warning for the southwestern two-thirds of the forecast area, with the Extreme Heat Watch in the northeast remaining.

- A few isolated showers and thunderstorms are possible (20-30%) tonight into Sunday morning. A few storms may be strong and produce hail or gusty winds, but the overall severe weather threat is low.

- Additional storm chances are possible Monday evening into Tuesday and again at times midweek.

SHORT TERM /THROUGH MONDAY/

Issued at 245 PM CDT Sat Jun 27 2026

Satellite imagery this afternoon shows an area of low to mid level clouds lifting north/northwest across the state, while upper level clouds shift northeastward overhead as well. Other than some areas of breaks in the cloud cover allowing for peaks of sunshine, most areas will continue to see clouds remain overhead. This is thanks to an increase in moisture coming from the south, with these clouds limiting the extent of warming so far today as temperatures have just recently reached into the low 70s across much of the forecast area. Given the slower warming, forecast highs have been reduced a bit more, with highs expected to top out later this afternoon in the upper 70s to low 80s across Central Iowa. The upper level pattern shows a deepening broad area of upper level troughing, which will continue to dive southeast across the western CONUS today, while weak ridging ahead of this feature is noted over the Midwest. A look at the surface pattern shows the development of two areas of low pressure: the first over Montana/Wyoming into the western Dakotas, and a smaller one south over Colorado and New Mexico, with Iowa generally remaining in the influence of light southeasterly flow associated with the subtle high pressure that will continue move away over the next several hours. The advertised pattern change is becoming imminent, as the western trough and surface low will continue to deepen into Sunday, paired with the arrival of a more pronounced upper level ridge into the southeastern CONUS. Ahead of this, the rest of today into Sunday is expected to remain generally on the dry side for many areas, outside of some low chances (around 20%) for scattered showers and isolated storms near over portions of Iowa, if at all. Specifically, the push of increased low level moisture into the Central Plains out of the south will continue into Sunday, with the southernmost area of low pressure developing further and gradually lifting northeast through the western Central Plains and into the upper Midwest. With weak forcing generally over the area, and limited moisture in the mid and upper levels where this elevated activity would occur leads to low confidence in occurrence. If showers and storms can develop over southern Iowa and lift northeast tonight into Sunday morning, some elevated hail would be the main concern given steep lapse rates over 7.5-8 C/km. Another area of showers and storms pass over far northwest Iowa into South Dakota into Minnesota where the better forcing is located.

Cloud cover will gradually decrease by late morning into the afternoon Sunday, with an increase in low level southwesterly flow allowing for the beginning of our expected heatwave to settle over Iowa. Forecast highs are expected to reach into the mid to upper 90s into the afternoon, paired with heat index values around 100-110 degrees across the southwestern two thirds of the state. This has lead to the upgrade of our Extreme Heat Watch into an Extreme Heat Warning for these areas, while much of northeast Iowa remains in an Extreme Heat Watch given slightly lower values but will likely be upgraded as well by this evening or early Sunday, as similar impacts are expected. Those who plan to partake in any outdoor activities need to make sure to take frequent breaks in the shade, stay hydrated and check on sensitive populations (pets, children, elderly folks, etc), as heat illness or worse can come on quickly in these conditions. Outside of minimal chances (<20%) for showers in the far northeast into the evening, dry conditions into Monday, as well as overnight lows in the upper 70s across the area will prolong the effects of this expected heat wave.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Issued at 245 PM CDT Sat Jun 27 2026

The upper level pattern changes very little through the early work week, with the longwave trough across the western CONUS becoming centered over the Desert Southwest, while the extra-tropical high lifts further north into the Ohio Valley and associated heat dome expands across much if not all of the eastern and central CONUS. Excessive heat will continue to impact all of Iowa, as forecast highs are expected to top out each day into the mid to upper 90s, paired with heat indices up to 110 degrees. Given the expectancy of this oppressive heat over several days and little recovery overnight as lows repeatedly only ''cool'' into the 70s, the Extreme Heat Warning is warranted to continue at least through Tuesday were confidence remains on the higher side, again with the likely expansion of this headline to include the entire portion of the DMX forecast area. Safety measures as discussed above need to remain in practice to avoid negative effects of this conditions that can quickly become dangerous. Outside of this heat, another area of developing surface low pressure is expected to lift northeast across the Central Plains, with an associated boundary moving into northwest Iowa by Monday evening. While deterministic models generally agree on the general area of this boundary, the extent of development of showers and storms remains more uncertain given lack of moisture above the more stable near surface layer. Any storm development that can occur would generally hold concerns for large hail given high instability and steep lapse rate profiles, along with gusty winds into Tuesday morning. The Slight Risk per SPC remains over northwest Iowa given this potential, with at least slight adjustments anticipated over the coming days. Additional chances of evening/overnight convection are signaled again Tuesday night into Wednesday, though confidence is lower to discuss coverage and intensity details in this forecast package, given this is still days away but worth keeping an eye on.

Above average temperatures are expected to remain in the forecast into the mid-late week period, with current forecast highs generally in the low to mid 90s and heat indices over 100 degrees. The expansion of heat headlines will be assessed beyond Tuesday in the coming days, with the likelihood of expansion quite probable. Additional chances for showers and storms are also indicated as a few shortwaves as suggested per long term guidance pass through within a growing area of upper level ridging over the Central Plains and Midwest, while a troughing pattern generally remains across the western CONUS.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1042 PM CDT Sat Jun 27 2026

MVFR cloud cover has expanded across Iowa with pockets of IFR ceilings developing this evening. IFR ceilings will expand through the overnight before improving through the day on Sunday. Winds increase overnight with gusts of 20+ kts by 12z and increasingly southerly winds gusting 25-30 kts 12z through the rest of the TAF period. Confidence is increasing in a thunderstorm complex moving across northern Iowa early SUnday morning with impacts to KFOD/KMCW. Confidence in the exact track and strength by the time these reach Iowa is low, however recent trends and the current environment support strong to severe storms persisting into Iowa Sunday morning.

DMX WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 1 PM Sunday to 9 PM CDT Tuesday for IAZ004-005-015-023>025-033>037-044>050-057>062-070>075-081>086- 092>097. Extreme Heat Watch from Sunday afternoon through Tuesday evening for IAZ006-007-016-017-026>028-038-039.