River Flood Warning 18, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
1053 PM CDT Tue Sep 8 2026

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Reintensification expected along a cold front moving across
  Iowa this afternoon and early evening. A few strong to severe
  storms may produce gusty winds a pockets of heavy rain.
  Showers linger across southern/southeastern Iowa through
  Wednesday morning.

- More seasonal temperatures in the upper 70s to low 80s the
  rest of this week.

- Additional thunderstorm chances later Friday into Saturday and
  again Sunday into early next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 226 PM CDT Tue Sep 8 2026

A line of showers has lingered across north central Iowa through the
morning and into the early afternoon, very slowly sinking toward
central Iowa. Warm air advection in the warm sector of the low is
ongoing with station in far southern Iowa reporting temperatures
into the low to mid 90s this afternoon. This has allowed for
destabilization ahead of the boundary with MLCAPE around 1500-2000
J/kg already. This prefrontal convection will continue to bubble
this afternoon ahead of the main cold front that has just reached
far northwest Iowa around 2 pm. Daytime heating should help to
reinvigorate the ongoing convection as it reaches central Iowa and
there is a window from around 21-03z for stronger storms to develop.
Any stronger cores would primarily present a damaging wind concern
with dry low levels noted in soundings lending a microburst
potential. Those would be fairly short lived. Shear is largely
parallel to the boundary, but if a bowing segment could orient
moving ENE with the shear a more organized wind signal could
develop. SPC has also outlined a 2% tornado risk. This would be
difficult to come by in this environment with parallel shear and
LCLs over 1200 m but stretching with initial updrafts may carry
some risk.

There is also a hydro concern this evening and overnight. The
environment is fairly supportive with PWATs of 2-2.25" (very high
for this time of year) and deep warm cloud layers over 4500 m for
efficient rain production. The 12z HREF indicated a widespread
1- 1.5" for much of the area with areas east of I-35 potentially
seeing pockets of 2-4+". CAMs through today have consistently
indicated pockets of 4-5+" are possible, though placement is
tougher to nail down. After the initial increase in
strength/coverage with daytime heating, secondary rejuvenation
of cores is anticipated as the LLJ increases overnight. Shear
parallel to the boundary will help allow for training cells,
tough the boundary itself will continue to sink south overnight
with not current indication of it stalling out. Based on where
ongoing convection is lining up and expectations for diurnal
strengthening and LLJ enhancement, somewhere in the highway 30
to I-80 corridor seems to be the most expected area. While
antecedent conditions are quite dry, areas in town with poorer
drainage could see a flash flood concern later this evening and
overnight.

Post-frontal showers linger across southern Iowa Wednesday morning
before finally exiting the area. In northern Iowa, patchy fog
is possible Wednesday morning behind the front and cooler air
filters into the area. Wednesday highs will be more seasonal in
the low 80s and these temperatures are expected to last through
the end of the week.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 226 PM CDT Tue Sep 8 2026

After a drier period Thursday and much of Friday, our next system
arrives later Friday into Saturday as a deepening shortwave
traverses the area. SPC has outlined a Day 4 risk area for this as a
plume of instability increases in conjunction with better kinematic
forcing. Another more robust system looks to move across the area
Sunday into early next week. Both system will help to bring
temperatures down and by early next weeks highs may be in the
upper 60s to low 70s areawide.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1041 PM CDT Tue Sep 8 2026

Showers and storms are continuing to clear through the area
which will mainly impact KDSM and KOTM through the night. If a
stronger storm is over either of these TAF sites, IFR visibility
restrictions are possible. This has been handled in TEMPO
groups which highlight the most likely period for stronger
storms over the terminals. Otherwise, across northern terminals,
patchy fog is possible leading to visibility reductions at KMCW
and KALO. The signal for fog is weaker at KFOD at this time. A
front will pass through the state through the day tomorrow,
leading to winds from the northwest towards the later half of
the period. With this, higher ceilings above FL100 are expected.

&&

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

&&

SHORT TERM...Hagenhoff
LONG TERM...Hagenhoff
AVIATION...67

Hazardous Weather Outlook
National Weather Service Des Moines IA
154 PM CDT Tue Sep 8 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-091500-
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-
154 PM CDT Tue Sep 8 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

The Heat Index will hover near or just over 100 degrees across
much of southern Iowa late this afternoon and early evening before
diminishing.

Showers and thunderstorms will become more widespread across much
of the area by this evening and into tonight, then be located
mostly over southern Iowa by sunrise Wednesday. A few of the
storms may be severe this evening, with damaging winds the primary
threat but also hail and even an isolated tornado remaining
possible.

Locally heavy rainfall could also lead to flooding in some areas
from this evening through tonight.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorm chances return to the forecast from late Friday
through the weekend. Any severe weather potential during this time
will be assessed in the coming days.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed later today.

&&

NWS Des Moines will discontinue the Hazardous Weather Outlook
product (HWO) on September 30th, 2026. Weather hazards and
outlooks will continue to be provided through the standard
forecast channels, including weather briefing packets, forecast
discussions, weather story graphics, the experimental graphical
hazardous weather outlook, and updated hazard messaging. All
local products and visual tools are accessible directly at
weather.gov/desmoines.

Lee

Preliminary Local Storm Report
National Weather Service Des Moines IA
822 PM CDT Tue Sep 8 2026

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

0620 PM     Tstm Wnd Dmg     2 NW Des Moines         41.59N 93.64W
09/08/2026                   Polk               IA   Amateur Radio

            Amateur radio report of trees down near Iowa
            Methodist Medical Center. Time estimated by
            radar.

&&

67

Preliminary Local Storm Report
National Weather Service Des Moines IA
837 PM CDT Tue Sep 8 2026

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

0620 PM     Hail             Mitchellville           41.66N 93.36W
09/08/2026  E1.75 Inch       Polk               IA   Public

            Picture sent in via social media.

&&

TDR

Preliminary Local Storm Report
National Weather Service Des Moines IA
905 PM CDT Tue Sep 8 2026

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

0624 PM     Tstm Wnd Dmg     2 NNW Mitchellville     41.69N 93.37W
09/08/2026                   Polk               IA   Public

            Grain silo destroyed and siding from a
            nearby building torn off. Time estimate via
            radar.

&&

TDR