Severe Thunderstorm Warning 166, NWS Des Moines, IA

832 
WWUS53 KDMX 170220
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
920 PM CDT Sat May 16 2026

IAC017-170245-
/O.CON.KDMX.SV.W.0166.000000T0000Z-260517T0245Z/
Bremer IA-
920 PM CDT Sat May 16 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 945 PM CDT
FOR EASTERN BREMER COUNTY...

At 919 PM CDT, a severe thunderstorm was located near Tripoli, or 11
miles east of Waverly, moving southeast at 10 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Sumner, Tripoli, and Readlyn.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4271 9237 4284 9233 4286 9208 4268 9208
TIME...MOT...LOC 0219Z 292DEG 10KT 4276 9224 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.25 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Donavon

826 
WWUS53 KDMX 170244
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
944 PM CDT Sat May 16 2026

IAC017-170253-
/O.EXP.KDMX.SV.W.0166.000000T0000Z-260517T0245Z/
Bremer IA-
944 PM CDT Sat May 16 2026

...THE SEVERE THUNDERSTORM WARNING FOR EASTERN BREMER COUNTY WILL
EXPIRE AT 945 PM CDT...

The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.  However, gusty
winds are still possible with this thunderstorm.

LAT...LON 4271 9237 4284 9233 4286 9208 4268 9208
TIME...MOT...LOC 0243Z 267DEG 9KT 4276 9216 

$$

Donavon

Area Forecast Discussion
National Weather Service Des Moines IA
701 PM CDT Sat May 16 2026

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

.KEY MESSAGES...

- Severe thunderstorm and heavy rain potential this afternoon
  into the evening, initially over south central Iowa then more
  widespread overnight into Sunday morning.

- Dry and breezy during the day Sunday. Additional storms
  develop in western and northwestern Iowa in the evening, then
  spreading eastward into much of Iowa overnight into Monday.

- One final round of storms expected later Monday into early
  Tuesday morning. Severe weather and heavy rainfall looks likely.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 330 PM CDT Sat May 16 2026

Current conditions in the central U.S. shows surface low pressure
over Kansas and the Texas & Oklahoma panhandles, advecting warm,
moist air up into southern Iowa. Farther north, a surface high is
working cooler, drier air south and east over Minnesota and northern
Iowa. On the periphery of these two air masses, a gradient of 2000
to 3000 J/kg of SBCAPE has developed from the I-80 corridor and
south, and is co-located with 40 to 50 kts of effective shear. A
subtle wind shift is in place along this region, and is expected to
become the focal point for storms this afternoon and evening.
Guidance has struggled with the placement of this wind shift and the
location of convective initiation still today, with the trend
seeming to be farther and farther south with each round of
guidance. Current consensus is that storms will fire over south
western into south central Iowa within the next few hours,
generally around 21 to 22z. These initial storms will have
access to the highly unstable and deeply sheared environment,
with access to 200+ m2/s2 of SRH within the 0-3 km layer,
supporting rotating updrafts and supercellular storms. DCAPE
values will also be modest, with SPC mesoanalysis implying 1000+
J/kg along southern Iowa. Both of these factors indicate a
potential for severe hail and strong winds with any of the
initial storms that develop. Rotating updrafts will also be
conducive for tornadogenesis, thanks to the 100+ J/kg of 0-3km
CAPE and low LCLs, but the low level wind fields do seem like a
limiting factor. The high 0-3 SRH is almost entirely driven by
the 1 to 3 km layer, while the lowest kilometer exhibits less
favorable easterly winds to the north of the wind shift and
minimal SRH from 0-1 km. That said, the southeasterly winds just
to our south would make for a low level wind field more
favorable for tornado development. Therefore, will need to watch
surface observations closely, as any discrete storms ingesting
that more southeasterly flow could lead to a better chance for
tornadoes.

Storms initially begin discrete this afternoon, but storm motions
along the boundary and the broad area of lift and instability
will lead to many competing updrafts and a conglomeration of
convection through the evening. This should mostly limit the
severe risk for our area, as we become cut off from the
uncontaminated warm sector. An east west oriented area of rain
and thunder will develop, likely over southern Iowa into
northern Missouri, resulting in a few hours of heavy rain within
the same areas that saw the initial storms. Healthy
precipitable water values in the 1.4" to 1.5" range will allow
for heavy rainfall in these areas. This, in conjunction with the
long duration of training storms, will lead to a swath of
higher rainfall amounts. Earlier this morning, this swath was
showing a widespread 2 to 3 inches of rainfall with some
embedded pockets of 5 inches or more. This afternoon, this same
signal still exists, but the southerly trend in guidance has
been pushing the heaviest swath along the Iowa/Missouri border
and southward. This should allow the heaviest rain to avoid the
Des Moines metro areas, and fall over more rural areas where
conditions have been dry and more capacity exists. That said, if
any of these pockets of heavy rainfall falls over a more urban
area/town, ponding on roads may still occur. Likewise, if the
bullseye of 6 to 7" that has shown up in a few CAMs occurs, even
in rural areas, some localized ponding or flooding could be a
concern. This has prompted a slight risk for excessive rainfall
from the weather prediction center over southern Iowa, although
the highest likelihood at this time still looks to be south of
our area.

Finally, as we get later into the evening, the guidance continues to
prog an MCS coming out of Nebraska and into western Iowa overnight
tonight into early Sunday morning. This MCS will roughly track along
the east west oriented area of rain as it lifts northward overnight,
leading to a roughly east northeasterly track across the area. Model
wind gust output and storm modes would suggest this north south
oriented line with the MCS could produce severe winds across
Nebraska but generally diminishes upon reaching Iowa early
Sunday morning. However, models are notoriously bad at modeling
MCSs so it's certainly within the realm of possibility that
these winds persist into Iowa as well. Fortunately, this time of
night will be lending itself to decoupling and more elevated
storms. Likewise, this will be moving into a fairly worked over
and less stable environment. Therefore, a diminishing trend
looks likely through Sunday morning, but not ruling out some
strong winds as it initially moves in.

The rain and thunderstorm activity moves out through Sunday morning,
with dry conditions expected over much of the state during the day
on Sunday. Relatively strong capping will inhibit the unstable
environment during the day, with storm development primarily
occurring in the evening and overnight hours. That said, gusty
conditions develop during the day Sunday across most of Iowa as
stronger winds aloft move into the area. Winds of 20 to 30 mph are
expected, with gusts nearing 40 mph possible at times.

Yet another round of thunderstorms will move into western Iowa in
the late evening to overnight hours Sunday as the surface low lifts
northeastward through Nebraska into western Iowa. This synoptic lift
and weakening cap will allow storms to go over northwestern Iowa,
with potential for more supercells capable of producing large hail,
damaging winds and tornadoes. That said, by the time these storms
look to arrive in our forecast area, the instability will be
diminishing and storms congealing into a line. Therefore, the
main tornado threat will be over far western and northwestern
Iowa Sunday evening, with mostly a wind threat farther eastward
into Iowa through the overnight hours. Driven by the low level
jet, storms persist overnight into early Monday, but the severe
risk looks fairly isolated.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 330 PM CDT Sat May 16 2026

The encore system will lift through the area on Monday, bringing the
potential for widespread storms and heavy rainfall. Severe weather
looks likely with this system, as the parameter space boasts 60+
dewpoints, very unstable, surface based conditions, and a good
amount of kinematic support along the cool front passing west to
east through the area. All severe hazards will be possible,
including hail, damaging winds and tornadoes. Strong moisture
transport will also lift into the warm sector of the Monday system,
bringing plenty of liquid into the area. Storms should be fairly
progressive along the cold front, but localized ponding or flash
flooding is certainly possible, especially in areas that receive
rainfall tonight and Sunday night as well. Likewise, more water
being added to local rivers could lead to in-bank rises through next
week. We then see a brief break in the active pattern through the
middle of the week, with milder temperatures overhead.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 645 PM CDT Sat May 16 2026

Thunderstorms have developed over southern Iowa and are
starting to lift towards KOTM. Additional scattered
showers/storms are expected to continue to develop through the
evening with more widespread activity moving in overnight. There
remains less certainty with where/when scattered activity,
outside of the storms in southern Iowa, will develop thus used
mix of tempo or prob30 groups where certainly is less. Updates
are expected as confidence in coverage/timing increases. The
activity overnight will likely be accompanied by lowering
visibilities with heavy rain at times, and overall lowering
ceilings with MVFR to even IFR conditions at times in portions
of central to northern Iowa. Strong wind gusts are also
possible, but are not currently reflected due to lower
confidence in timing and intensity. Precipitation moves out
Sunday morning with windy conditions out of the south-southeast
expected during the day.

&&

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

&&

SHORT TERM...Dodson
LONG TERM...Dodson
AVIATION...05

Hazardous Weather Outlook
National Weather Service Des Moines IA
243 PM CDT Sat May 16 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-171945-
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-
243 PM CDT Sat May 16 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

There is a Slight Risk (level 2 of 5) for severe storms today.
All modes of severe storms are possible. Storms are expected to
develop in south central Iowa late this afternoon, continuing
across Iowa overnight through Sunday morning.

Heavy rainfall is expected to occur at times this evening into
early Sunday, largely over far southern Iowa. Flash flooding
concerns are limited, with the highest risk in urban areas.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

An active weather pattern will continue Sunday and Monday, with
chances for severe thunderstorms both days. Details of timing,
location, and hazard types will be better determined in the coming
days as each day of storms will impact details of the next.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed at times through Monday.

Preliminary Local Storm Report
National Weather Service Des Moines IA
600 PM CDT Sat May 16 2026

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

0554 PM     Tornado          1 SE Gravity            40.75N 94.73W
05/16/2026                   Taylor             IA   Storm Chaser

&&

Ansorge

Preliminary Local Storm Report
National Weather Service Des Moines IA
623 PM CDT Sat May 16 2026

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

0620 PM     Hail             3 SSE Plano             40.72N 93.04W
05/16/2026  E0.88 Inch       Appanoose          IA   Trained Spotter

            dime to nickel sized hail.

&&

RD

Preliminary Local Storm Report
National Weather Service Des Moines IA
645 PM CDT Sat May 16 2026

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

0628 PM     Hail             3 SE Gravity            40.72N 94.73W
05/16/2026  E1.00 Inch       Taylor             IA   Public

            Report from mPING: Quarter (1.00 in.).

&&

Preliminary Local Storm Report
National Weather Service Des Moines IA
654 PM CDT Sat May 16 2026

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

0545 PM     Hail             2 N Gravity             40.79N 94.74W
05/16/2026  M2.75 Inch       Taylor             IA   Trained Spotter

            Caliper measured 2.83 hail. Relayed by WOI.

&&

RD

Preliminary Local Storm Report
National Weather Service Des Moines IA
712 PM CDT Sat May 16 2026

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

0706 PM     Hail             Mount Ayr               40.71N 94.24W
05/16/2026  M1.00 Inch       Ringgold           IA   Trained Spotter

&&

Preliminary Local Storm Report
National Weather Service Des Moines IA
716 PM CDT Sat May 16 2026

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

0714 PM     Hail             Mount Ayr               40.71N 94.25W
05/16/2026  E1.75 Inch       Ringgold           IA   Trained Spotter

&&

RD