textproduct: Des Moines

KEY MESSAGES

- First stretch of oppressive heat of the Summer begins on Sunday and continues into next week, likely continuing into the upcoming holiday weekend. Record high overnight lows Mon- Tue will amplify impacts by negating typical overnight recovery.

- Scattered showers and storms Saturday evening and overnight. A few storms may become severe containing hail and/or damaging winds.

- The heat wave may be disrupted briefly by overnight thunderstorm chances next week, especially in western and northern Iowa. Locations and which night offers the best chance will be refined over the coming days.

SHORT TERM /THROUGH SATURDAY/

Issued at 200 PM CDT Fri Jun 26 2026

A major pattern change shaping up for the CONUS this weekend as a 250mb 150kt jet carves out a longwave trough across the west. The downstream result will be to strengthen the southeast CONUS sub- tropical high pressure. In between, flow will turn southwest and amplify accessing a reservoir of heat and moisture; and advecting it into the Midwest.

In the meantime while the pattern changes, clouds will be on the decrease central and north tonight, but will likely hang around in the south. Latest short range guidance suggests some patchy fog after midnight in southern Iowa, so have added it for a brief time centered around sunrise Saturday. Otherwise, Saturday morning will feature the last morning with temperatures in the 60s for the next week at a minimum - and likely longer.

Bottom line - if you have things to get done outdoors and you don't want to do them in hot and muggy conditions; Saturday is your day. Temperatures will be seasonal with less clouds north and more in the south.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/

Issued at 200 PM CDT Fri Jun 26 2026

On Saturday night, the flow backs as the aforementioned pattern amplifies. In doing so, the initial surge of theta-e arrives on the leading edge of an eastward advancing EML. Mid-level lapse rates steepen as a result, and when combined with weak shortwave energy moving overhead should be able to spark scattered showers and thunderstorms Saturday evening and overnight. Severe threat is largely conditional depending on timing and isn't expected to be widespread. However, it can't be ruled out either with progd MUCAPEs in excess of 2000 j/kg and adequate deep-layer shear. If storms are able to organize, elevated hailers to be the primary threat, with gusty winds a secondary hazard, especially when storms collapse.

Heat will become the main focus for Sunday and beyond as a well established EML puts a lid on any convection potential. Temperatures will warm and dew point temperatures will climb as the advective trajectory is directly into the Midwest. Additionally, we're entering the beginning of the corn evapotransportation period, which will be additive to the dew points. NBM output is undoubtedly a bit "hot" on high temperatures, however the resultant impact on heat indices should be minimal, given that its likely underdoing of dew points too. As a result heat indices are expected to climb above 100F beginning Sunday and continuing into early next week. A heat headline will be needed for this period as area and hazard type (warning or advisory) is more clear. Record high overnight low temperatures that is only expected to fall into the mid- upper 70s will amplify impacts.

How the pattern amplifies and the position of the sub-tropical high pressure will dictate any overnight thunderstorm potential. Undoubtedly there will be overnight convection set up somewhere, at this point it appears the best chance would be in west and north sections of the state. However, clarity on this won't be known yet for a few days.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 624 PM CDT Fri Jun 26 2026

A cloud deck lifting northward into southern Iowa is producing MVFR and occasional IFR ceilings near KOTM. This is expected to continue northward through the next few hours, reaching KDSM this evening. Recent guidance is starting to suggest that these low ceilings (and MVFR conditions) could span to all sites, including KFOD, KMCW, and KALO by tomorrow morning. However, this is an inconsistent signal and therefore confidence is lower, so have only mentioned scattered MVFR ceilings at these sites. In addition to the low ceilings near KDSM and KOTM, a light fog/mist is also possible by tomorrow morning. Finally, winds generally remain light out of the east to southeast, increasing out of the southeast through Saturday.

DMX WATCHES/WARNINGS/ADVISORIES

None.