textproduct: Des Moines

KEY MESSAGES

- Showers and storms arrive early this afternoon in western Iowa, then more widespread storms arrive tonight. The severe weather threat is low.

- Next best chance of rain will be Thursday night in southern IA.

- Additional storm chances this weekend with warmer temperatures on the way.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 328 AM CDT Tue Jun 23 2026

Stratus has lingered in northern Iowa overnight, which will keep lows closer to 60 degrees this morning. Upstream, thunderstorms formed in response to the trough ejecting in from Canada. Lee side troughing is disrupting moisture transport towards the northern Plains. This has negative impacts on thunderstorm activity later today. 850mb dew points may inch above 10C on the cold front this afternoon, which will be just enough to generate 1000 J/kg of CAPE in the Dakotas. The first glance at precipitation will be in western Iowa around midday; this is leftover debris from overnight convection. The frontally-forced storms and instability will move in later this evening. Poor lapse rates (<7 C/km) will decrease thunderstorm activity and severity, and more favorable deep-layer shear lags behind the front. The Marginal Risk is just outside the DMX CWA for these reasons.

Will need to watch for more thunderstorm activity in northern Iowa on Wednesday. The low-level moisture field will get pulled away from the lee cyclone slightly, with a small plume advecting towards the trough in Minnesota. CAPE values in Iowa look comparatively better than the night before, exceeding 1000 J/kg. While the front from overnight will be in eastern Iowa by the afternoon, the air left behind will be dry and will mix well in the afternoon, presenting an inverted V sounding. The influence of the upper-level trough will sink into northeast Iowa through the afternoon, the same time as the left exit region of the upper jet enters the picture. Current thinking is that the weak midlevel lapse rates and broad lift will support smaller updrafts in peak heating hours. These storms will produce lightning and some gusty winds due to the dry sub-cloud layer.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 229 PM CDT Mon Jun 22 2026

The upper level flow pattern will remain mostly zonal/westerly much of this week before an upper closed low descends into the western CONUS while a sub-tropical highs forms across the southeast CONUS. This setup will default southwest flow over Iowa initially. That flow will become progressively steeper as the high pushes westward towards the lower Mississippi Valley. This will result in seasonably cool conditions much of the work week followed by warmer and more humid conditions by late this weekend and into early next week. There will be a few chances for showers and storms with weak impulse passage Friday then a greater chances with the main warm advection arrival Saturday night/Sunday.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 640 AM CDT Tue Jun 23 2026

VFR conditions early this morning with VFR stratus over KMCW and KALO. Clouds will increase across the area today, which will be cloud debris from storms in South Dakota this morning. Confidence is low in showers with these clouds, as storms are expected to fall apart.

A cumulus field will develop today and may present brief MVFR BKN decks at sites in the first two hours of formation. Confidence hedged more towards SCT for now.

Refined timing of shower arrival after 00z tonight with the greatest chance for thunderstorms at KMCW. Activity will sink south and east with time, reaching KDSM right at the end of the TAF period.

DMX WATCHES/WARNINGS/ADVISORIES

None.