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 THURSDAY/

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 /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1255 PM CDT Fri Jun 26 2026

Expect mainly VFR conditions to prevail through the period. Some mid-level clouds will linger through the day, although northern Iowa terminals should see those decrease too. Short-range guidance has began to hint at the potential for lower ceilings and/or localized fog at KDSM and KOTM for a few hours centered around 11Z Saturday. Have included a SCT deck to begin trending that way. If confidence increases on occurrence, may need to continue the trend. Otherwise, winds will be out of the SE or E at less than 10 knots through the period.

DMX WATCHES/WARNINGS/ADVISORIES

None.