Severe Thunderstorm Warning 109, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
631 PM CDT Mon Jun 16 2025

...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Scattered strong to severe thunderstorms this evening.
  Damaging wind gust and hail are the main hazards.

- Periods with thunderstorms, some strong will continue into
  Tuesday night and early Wednesday.

- Areas with heavy rainfall also likely through Wednesday with
  the focus shifting south into central and southern Iowa.

- Turning hot and humid late week and into the weekend.

&&

.DISCUSSION...
Issued at 243 PM CDT Mon Jun 16 2025

Storms are still ongoing over parts of the northeast county warning
area including near Waterloo. This convection has been moving slowly
east/southeast since earlier this morning as it fired along an
outflow boundary from overnight storms. A few of the storms have
been strong and near severe and they are beginning to have stronger
cold pools associated with them, as indicated by the the 20+ degree
drop in temperatures. Wind gusts have responded as well with a few
gusts of 40 to 55 mph now being recorded. These storms have also
produced rainfall amounts of 1-2 inches. A pseudo boundary has setup
also as a result of the storms with south/southwest wind and
temperatures in the mid 80s mainly south of Highway 20 to near
Waterloo to Fort Dodge then arcing northwest into Minnesota.

The convective allowing models (CAMs) have not performed well today
and outside the HiRes ARW, the remainder of the CAMs have combined
for a near zero batting average on this mornings convection and the
new convection firing over southeast South Dakota along the primary
cold front. The lack of consistency with the CAMs and the turned
over air north and the pseudo boundary a bit south, the confidence
on the evolution of storms going into this evening is lower than
normal. Once potential outcome is the storms over southeast South
Dakota become rooted and then travel southeast along the pseudo
boundary where and instability axis is situated and eventually move
into central Iowa this evening. Otherwise, it could be a waiting
game for the development of an MCS over Nebraska mid to late
evening, though that system should turn southeast. The main cold
front will move into Iowa tonight and stall somewhere over central
Iowa. That will eventually become the focus for storm development
overnight or through the day Tuesday. The triple point will move
into should move into south central Iowa late Tuesday into Tuesday
night which may bring the tornado threat into the state.

Heavy rain potential will remain through Wednesday. The strongest
moisture advection will remain just south of Iowa but PWATs in
excess of 2" will be over Iowa at times from late Tuesday into early
Wednesday. Warm cloud depths by Tuesday night will be approaching 13
kft so efficient warm rain processes and slow storm motions will
lead to areas with heavy rainfall. At this point, much of the heavy
rain has been over northern Iowa. That focus should shift south into
central and southern Iowa. Will continue to monitor the situation as
several streams are running above normal.

After the short wave passage on Wednesday, 500 mb heights will be on
the increase and a transition to a very warm and humid pattern will
occur. High temperatures in the 90s with dew points in the 70s at
times will be the warmest weather so far this year. Eventually the
upper flow will undergo another transition late weekend into early
next week with a large upper high developing to the east and and
upper low to the west and southwest upper flow into Iowa. One period
to watch is Thursday night as this transition occurs as an MCS could
develop over Minnesota and drop southeast into Iowa. Otherwise, the
next convective chances, barring the presence of a stout enhanced
mixed layer (EML), will be next week, which may be stormy at times
after a lull late week and into the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 631 PM CDT Mon Jun 16 2025

Lower confidence forecast with guidance not handling the current
picture well, but in the near term have timed out storms to FOD
as well as MCW with a PROB30 for storm potential. Will have to
monitor trends through the evening and make AMD as needed.
An uptick in shower and storm chances is expected Tuesday
afternoon and for now have advertised as prolonged SHRA/TSRA at
the terminals.

&&

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

&&

DISCUSSION...Donavon
AVIATION...Ansorge

Hazardous Weather Outlook
National Weather Service Des Moines IA
404 AM CDT Mon Jun 16 2025

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-170915-
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-
404 AM CDT Mon Jun 16 2025

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Scattered thunderstorms are expected again today, with stronger
and more widespread storms during the afternoon and evening. Some
storms this afternoon and evening may be severe, with hail,
damaging winds, and tornadoes all possible. Localized heavy rain
may also lead to ponding of water.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Severe storms are again possible on Tuesday, with gusty winds, hail,
and tornadoes possible. Heavy rainfall is also expected, which
will add the potential for flash flooding and river rises.

Additional rounds of storms are expected through the week. Details
on these later storms will become clear er in the coming days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

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Preliminary Local Storm Report
National Weather Service Des Moines IA
642 PM CDT Mon Jun 16 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0642 PM     Hail             Pomeroy                 42.55N 94.68W
06/16/2025  E0.75 Inch       Calhoun            IA   Trained Spotter

&&

Ansorge