textproduct: Des Moines

KEY MESSAGES

- Low potential (20%) for isolated showers and thunderstorms in northeast Iowa later this morning to afternoon.

- Heat and humidity continues into this weekend. The Heat Advisory has been expanded another row of counties in north central Iowa. The heat headlines are in effect through Saturday.

- Low storm chances (10%) Saturday morning to afternoon in western Iowa. On and off storm chances continue into early next week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 311 AM CDT Fri Sep 4 2026

Dry but warm conditions keep hold early this morning across Central Iowa, with partly to mostly cloudy skies as temperatures as of 2am sit through the 70s, paired with dewpoints in the upper 60s to low 70s. Broad mid to upper level ridging remains the primary feature overhead, which is largely draped across the central to eastern CONUS. Within the apex of this ridge is a shortwave trough that is over the Upper Midwest region, with an area of strong 925mb frontogenesis paired with notable upper level divergence across Wisconsin through Central Minnesota, which has led to ongoing strong to severe storms over these areas. Through the rest of this morning and into the afternoon, the expectation is that this shortwave will track eastward, with lingering shower and storm activity expected to continue southeast with time. While most of this activity should remain north and east out of Iowa, there is remaining potential (20%) near sunrise to see storm development into northeast Iowa. Weak forcing however overhead and low level dry air however will likely keep storm development, if any, more isolated and short lived later this morning and even into early afternoon. Cannot rule out gusty winds though given the aforementioned dry low levels as any storms collapse, though the concern for severe weather continues to decrease. Outside of the low storm potential, the main weather story continues to be the late summertime heat and humidity, thanks to the nearby heat dome that continues to dominate over much of the country. Forecast highs are on track to reach into the low to mid 90s this afternoon, with heat indices up to 100-105 most likely over southern to central Iowa, but also trending even further north to include much of north-central Iowa as well given latest trends. Therefore, have included another row of counties (Sac to Black Hawk) in north-central Iowa in a Heat Advisory this afternoon through Saturday.

The start of the weekend will see little change in the overall synoptic pattern, with the ridge building northward slightly. A strengthened low level jet is anticipated to point due north across Kansas through the Dakotas, where morning convection per CAMs is anticipated to occur. Trends keep this activity mainly west of Iowa, but some members suggest some storms making it into western Iowa into the late morning to afternoon. If storms can develop, a favorable environment featuring instability values around 3000-4000 J/kg and lapse rates around 7.5 C/km could lead to potential isolated severe weather, though given lack of forcing overhead and weak shear, the chances are quite low (10%). Will continue to monitor trends and adjust accordingly. Otherwise, dry conditions should generally prevail Saturday, with forecast highs again in the low to mid 90s and heat indices up to 100-105 degrees into the afternoon. Heat headlines therefore continue through this timeframe as well.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 211 PM CDT Thu Sep 3 2026

A more robust trough will move east across the northern US from Sunday into early next week. This will renew the periodic scattered thunderstorms chances each day while also helping to squash the thermal ridge. We will not see substantial cooling, however temperatures Sunday into early next week should be at least a few degrees cooler than what we have seen this week. The ridge does look to rebuild for the middle to end of next week. Heat and humidity along with continued scattered thunderstorm chances looks to be the story for at least another week.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1052 PM CDT Thu Sep 3 2026

Main change this issuance was introducing LLWS to more sites tonight, which will range between 35 and 40kts. Have delayed rain at KMCW in the Prob30 group. Most of this activity will remain north of the site. There is <10% chance of thunderstorm development after 20z, highest confidence at KALO, but could also affect KMCW and KDSM. Will continue to monitor trends.

DMX WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 1 PM this afternoon to 7 PM CDT Saturday for IAZ033>039-044>050. Heat Advisory until 7 PM CDT Saturday for IAZ057>062-070>075- 081>086-092>097.