Severe Thunderstorm Warning 246, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
249 PM CDT Mon Sep 22 2025

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Slight risk (15%) for severe storms mainly northern and
  western Iowa this evening. Marginal risk elsewhere. Damaging
  winds, hail, and a tornado or two possible.

- Storm chances continue south Tuesday, but the threat for
  severe weather is low (<5%).

- Dry and mild from Wednesday into the weekend.

&&

.DISCUSSION...
Issued at 116 PM CDT Mon Sep 22 2025

Main forecast concern today is on the potential for storms
tonight. Initial focus is on front draped near the IA-MN border.
High resolution models continue to depict storms developing
along the boundary between 4pm and 6pm then slowly migrating
south during the evening. This evolution is supported by
moisture pooling along the front in northern Iowa with dew
points already in the 67-70F range and surface based CAPE ahead
of the front around 3000 J/kg. Ample sunshine will also
continue to destabilize the atmosphere near the boundary as we
head into late afternoon. Mid level lapse rates are slowly
increasing, progged to reach 7-8 C/km by 00z. This would suggest
updrafts capable of supporting large hail this evening. And as
with any boundary, a tornado cannot be ruled out where storms
are tied to the boundary.

Looking to the west, an upper level wave approaching out of
Nebraska will help destabilize the atmosphere over western
Iowa. Storms are expected to develop over Nebraska and move east
into Iowa during the late evening hours. Large hail will remain
a concern with cooling aloft associated with the incoming wave
along with damaging wind with DCAPE from 1000 to 1400 in western
Iowa this afternoon.

Another concern is potential for heavy rain. With the slow
movement of the front, there is potential for heavy rainfall.
PWATs are in the 1-1.5 inch range. and with opportunity for
multiple rounds of storms, training could result in locally
heavy rainfall with impacts more likely in urban areas.

Tuesday chance of storms continues in the morning over
southern portions of the state. Chance for severe storms
tomorrow is limited.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 116 PM CDT Mon Sep 22 2025

Unsettled pattern for the next 24-36 hours across the region as
a cold front slowly drops south across Iowa. Result will be
periods of storms this evening through the overnight hours.
Storm have the potential to produce large hail and gusty wind.
Introduced prob30 for TSRA at all TAF sites during the period
of most likely tstorm activity. In the wake of the storms, will
need to watch for potential fog development due to light surface
winds and high humidity; although confidence too low to mention
in TAFs at this time due to expected cloud cover.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION...DMD
AVIATION...DMD

Hazardous Weather Outlook
National Weather Service Des Moines IA
515 PM CDT Mon Sep 22 2025

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-232215-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
515 PM CDT Mon Sep 22 2025

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

A few strong to severe storms are possible this evening though 3
am. The greatest chances for severe storms is over parts of west
central and into north central Iowa. Large hail up to half dollar
sized and damaging wind gusts of 60 mph or greater are the primary
threats.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms will remain in the forecast over the southern half
of Iowa Tuesday and Tuesday night. At this time, the threat for
any severe weather looks low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible this evening.