Severe Thunderstorm Warning 173, NWS Des Moines, IA

667 
WWUS53 KDMX 290458
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
1158 PM CDT Fri Jul 28 2023

IAC007-051-135-179-290515-
/O.CON.KDMX.SV.W.0173.000000T0000Z-230729T0515Z/
Monroe IA-Wapello IA-Davis IA-Appanoose IA-
1158 PM CDT Fri Jul 28 2023

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1215 AM CDT
FOR SOUTHEASTERN MONROE...SOUTHWESTERN WAPELLO...NORTHWESTERN DAVIS
AND NORTHEASTERN APPANOOSE COUNTIES...

At 1157 PM CDT, a severe thunderstorm was located near Blakesburg, or
8 miles southwest of Ottumwa, moving southeast at 35 mph.

HAZARD...60 mph wind gusts and penny size hail.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
  Drakesville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4093 9273 4106 9255 4093 9229 4075 9255
TIME...MOT...LOC 0457Z 309DEG 28KT 4095 9255 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Dodson/MF

047 
WWUS53 KDMX 290513
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
1213 AM CDT Sat Jul 29 2023

IAC007-051-135-179-290522-
/O.EXP.KDMX.SV.W.0173.000000T0000Z-230729T0515Z/
Monroe IA-Wapello IA-Davis IA-Appanoose IA-
1213 AM CDT Sat Jul 29 2023

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN MONROE...
SOUTHWESTERN WAPELLO...NORTHWESTERN DAVIS AND NORTHEASTERN APPANOOSE
COUNTIES WILL EXPIRE AT 1215 AM 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 4093 9273 4106 9255 4093 9229 4075 9255
TIME...MOT...LOC 0512Z 308DEG 25KT 4089 9245 

$$

Dodson/MF

Area Forecast Discussion
National Weather Service Des Moines IA
1055 PM CDT Fri Jul 28 2023

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

.DISCUSSION.../Tonight through Friday/
Issued at 158 PM CDT Fri Jul 28 2023

FORECAST HIGHLIGHTS:

--Hot, humid today with heat headlines persisting into tonight.
--Storm chances later this afternoon into tonight and/or overnight
into Saturday. Some strong to severe storms possible this
afternoon/evening with large hail and damaging wind gusts the
primary threats.
--Cooler temperatures this weekend.
--Periodic storm chances at times into next week.

DISCUSSION:

Not a clear-cut forecast heading into the rest of the day and
tomorrow with models continuing to suggest multiple scenarios and
flip-flopping between most likely solutions run to run.

Let's start with what we know already. Upper-level pattern features
a strong high pressure over the southwest U.S. with near zonal flow
this morning that is expected to amplify into tomorrow as the ridge
builds over the western U.S. and a trough starts to deepen over the
eastern U.S. This leaves Iowa in west to northwest flow with
multiple waves continuing to drift through the overarching flow and
providing multiple opportunities for storms over the next several
days.

Focusing on the short term, midday surface analysis shows the
boundary near the IA/MN border in the north/east arching back
towards the IA/SD/NE border in the northwest. As expected, a warm,
moist airmass is south of this boundary with dew points well into
the 70s, some AWOS stations once again suggesting dew points in the
80s. Temperatures have also warmed into the upper 80s to 90s as of
midday resulting in heat indices well into the 100s, or overall
generally unpleasant. Midday satellite imagery shows two waves of
note, one moving eastward across northern Nebraska and the other
diving south out of the Upper Northern Plains with a second frontal
boundary associated with it. Mid-level temperatures in the +12 to
+14 range would suggest a capped environment is still in place over
much of the state as of ~18Z with 850mb analysis showing plentiful
moisture pooling in northern Iowa up towards the IA/MN border and
frontal boundary. The warm, moist airmass is leading to the
development of strong instability with ~18Z SPC mesoanalysis showing
3000-6000 J/kg of MUCAPE with equally impressive (though still
capped) MLCAPES in the 3000-4000 J/kg range. Given our abundant
CAPE, steepening lapse rates and bulk shear values in the 30-50 knot
range, the environment is absolutely supportive of strong to severe
storms this afternoon into tonight, with large hail, potentially 2"
or larger, a threat with initial, more discrete storms, before
storms likely congeal into more of a forward propagating convective
system(s) with damaging winds gusts becoming a greater concern as
storms continue into the evening. Although won't rule out
completely, the threat for tornadoes is low with LCL heights
generally too high and lower SRH values overall. Thus, any tornado
threat looks highly dependent on boundary interactions.

When and where the storms form is not quite as straightforward. The
most likely location for storms will be near the frontal boundary
with the incoming waves helping to provide the forcing to erode the
cap. Some 12Z data, like the 12Z HRRR seems to not be modeling the
environment well with dew points likely too low by later this
afternoon and thus not kicking storms off despite suggesting we'll
break through part of the cap by 21-23Z. Best guesses at this point
for storm formation location/timing are closer to some of the HRW
cores and/or NAMNest with storms forming through central/northern
Iowa and moving eastward with time into this evening.

Whether or not storms are able to form this afternoon into evening,
storm chances continue into tomorrow as the front shifts south with
the second wave/front coming into the area off of the Northern
Plains with yet another wave behind it incoming from WY/MT. What
happens with all of these waves is highly dependent on what happens
this afternoon/evening and whether or not the environment is worked
over into tomorrow morning. Do want to emphasize the possibilitiy
for additional storms overnight into early Saturday, especially
southwest/south which could have a conditional wind threat.
Influence of the low level jet overnight seems more uncertain with
models not consistent in location/strength and some models, like
the NAM, generally slower with the secondary wave which would
have storms not arriving until closer to midday Saturday.

With the uncertainty of storm timing/location, exact temperatures
tonight into tomorrow are more uncertain as well but we will at
least be able to ditch the heat headlines by/before the 9pm time
frame tonight with temperatures cooling through the weekend behind
the passage of the fronts as highs drop into the 80s again. A
surface high pressure does move towards the state from the north
into Sunday with a period of dry weather later this weekend though
as mentioned previously, periodic chances for storms continue off
and on into next week as waves round the overarching northwest flow
with additional details to be provided in future forecast
updates.

&&

.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1054 PM CDT Fri Jul 28 2023

Storms to exit southeast near OTM by 07z with lingering strong
storms though 05-06z. Most sites sct mid to high level behind
boundary with NW/NE winds generally under 12kts most of remainder
of period. Aft storms pass, expecting VFR conditions. Some
potential for storms aft 12z Sat, but at this time expect them to
miss any TAF sites. /rev

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

DISCUSSION...KCM
AVIATION...REV

Hazardous Weather Outlook
National Weather Service Des Moines IA
326 PM CDT Fri Jul 28 2023

IAZ033-034-044>050-057>062-070>075-081>086-092>097-292030-
Sac-Calhoun-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-
326 PM CDT Fri Jul 28 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

An Excessive Heat Warning is in effect for the area through
tonight. Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

Storms are possible by this afternoon and into tonight,
especially north of interstate 80. A few storms may be strong to
severe, capable of large hail and damaging winds.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Periodic chances for storms return late weekend and early next
week. The threat of severe weather is uncertain at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this evening.

IAZ004>007-015>017-023>028-035>039-292030-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Webster-
Hamilton-Hardin-Grundy-Black Hawk-
326 PM CDT Fri Jul 28 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A Heat Advisory is in effect for the area through tonight. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

Storms are possible by this afternoon and into tonight. A few
storms may be strong to severe, capable of large hail and damaging
winds. A tornado may be possible as well.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Periodic chances for storms return late weekend and early next
week. The threat of severe weather is uncertain at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this evening.

Hagenhoff

Preliminary Local Storm Report
National Weather Service Des Moines IA
922 PM CDT Fri Jul 28 2023

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

0835 PM     Tstm Wnd Dmg     1 SSE Toledo            41.98N 92.58W
07/28/2023                   Tama               IA   911 Call Center

            Trees down in Tama and Toledo.

&&

CAH

Special Weather Statement
National Weather Service Des Moines IA
1005 PM CDT Fri Jul 28 2023

IAZ061-062-074-075-290330-
Poweshiek IA-Marion IA-Jasper IA-Mahaska IA-
1005 PM CDT Fri Jul 28 2023

...Strong thunderstorms will impact portions of southwestern
Poweshiek, eastern Marion, Mahaska and southeastern Jasper Counties
through 1030 PM CDT...

At 1004 PM CDT, Doppler radar was tracking strong thunderstorms
extending from near Iowa Speedway to 4 miles south of Pella to 8
miles east of Knoxville. Movement was east at 40 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Oskaloosa, Pella, New Sharon, Lake Red Rock, Sully, Beacon,
University Park, Bussey, Lynnville, Harvey, Leighton, Reasnor,
Searsboro, Keomah Village, Pella Municipal Airport and Lake Keomah
State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until midnight CDT for
central Iowa.

&&

LAT...LON 4162 9264 4127 9252 4116 9266 4122 9309
      4136 9303 4164 9308
TIME...MOT...LOC 0304Z 286DEG 36KT 4162 9301 4135 9289 4128 9295

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

Dodson/MF

Preliminary Local Storm Report
National Weather Service Des Moines IA
1038 PM CDT Fri Jul 28 2023

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

0804 PM     Hail             2 WNW Marshalltown      42.05N 92.95W
07/28/2023  E1.00 inch       Marshall           IA   Public

            Delayed Report from mPING: Quarter (1.00
            in.).

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
1039 PM CDT Fri Jul 28 2023

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

0605 PM     Hail             3 NW Readlyn            42.74N 92.26W
07/28/2023  M1.25 inch       Bremer             IA   Public

            Delayed report - hail up to half dollar
            sized.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
1045 PM CDT Fri Jul 28 2023

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

1040 PM     Hail             4 NW Eddyville          41.19N 92.70W
07/28/2023  E1.75 inch       Mahaska            IA   Trained Spotter

            Golf ball sized hail.

&&

Fowle

Preliminary Local Storm Report
National Weather Service Des Moines IA
1126 PM CDT Fri Jul 28 2023

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

1124 PM     Hail             2 N Attica              41.26N 93.01W
07/28/2023  E1.00 inch       Marion             IA   Trained Spotter

            Largest stones were quarter sized.

&&

Fowle