Alert archive / Iowa / Flash Flood Warnings in 2023

Flash Flood Warning 12, NWS Omaha, NE

August 2, 2023Harrison County, Pottawattamie County, Shelby County, Iowa

NWS Omaha, NE issued this flash flood warning at Aug 2, 2023, 2:47 AM CDT for Harrison County, Pottawattamie County, Shelby County, Iowa. It was in force for 8 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 2, 2023, 2:47 AM CDT (07:47 UTC)
Expired
Aug 2, 2023, 10:21 AM CDT
In force
8 hr
Issued by
NWS Omaha, NE
Area
Storm-based polygon
Flood severity
None

Counties Harrison County, IA, Pottawattamie County, IA, Shelby County, IA

The radar

The Omaha radar (KOAX), 73 km from the middle of the area, began a volume at 07:47 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 7.8 hours before the alert went out and 73 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Omaha, NE at 00:00Z on 2023-08-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1026 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 00:00Z on 2023-08-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 66 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1026 J/kg
Mixed-layer CIN
-186 J/kg
Mixed-layer LCL
775 m above ground
0-6 km bulk shear
42 kt
0-1 km storm-relative helicity
66 m²/s²
0-3 km storm-relative helicity
185 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.9

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Omaha, NE wrote its last area forecast discussion before this flash flood warning went out at Aug 2, 12:00 AM CDT, 2 hours 47 minutes earlier.

Area forecast discussion, Aug 2, 12:00 AM CDT, 2 hours 47 minutes before
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Hazardous weather outlook, Aug 1, 9:37 PM CDT, 5 hours 10 minutes before
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In the hours before

Special weather statement, Aug 2, 1:59 AM CDT, 48 minutes before
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
159 AM CDT Wed Aug 2 2023

IAZ069-020715-
Pottawattamie IA-
159 AM CDT Wed Aug 2 2023

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL POTTAWATTAMIE
COUNTY THROUGH 215 AM CDT...

At 159 AM CDT, Doppler radar was tracking a strong thunderstorm 8
miles south of Walnut, or 8 miles west of Atlantic, moving east at 10
mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

This storm will remain over mainly rural areas of east central
Pottawattamie County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4128 9528 4146 9527 4147 9516 4139 9515
      4126 9516
TIME...MOT...LOC 0659Z 271DEG 8KT 4137 9518

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

DeWald
Special weather statement, Aug 2, 2:04 AM CDT, 43 minutes before
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
204 AM CDT Wed Aug 2 2023

IAZ069-020715-
Pottawattamie IA-
204 AM CDT Wed Aug 2 2023

...A STRONG THUNDERSTORM WILL IMPACT NORTH CENTRAL POTTAWATTAMIE
COUNTY THROUGH 215 AM CDT...

At 203 AM CDT, Doppler radar was tracking a strong thunderstorm near
Minden, or 18 miles southwest of Harlan, moving east at 25 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down small tree branches and blow
         around unsecured objects. Minor hail damage to vegetation
         is possible.

Locations impacted include...
Neola, Shelby, Minden, and Arrowhead Park.

This includes Interstate 80 in Iowa between mile markers 20 and 34.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4137 9564 4150 9565 4150 9540 4137 9540
TIME...MOT...LOC 0703Z 264DEG 20KT 4143 9554

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

DeWald
Special weather statement, Aug 2, 2:06 AM CDT, 41 minutes before
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
206 AM CDT Wed Aug 2 2023

IAZ055-069-NEZ045-020715-
Pottawattamie IA-Harrison IA-Washington NE-
206 AM CDT Wed Aug 2 2023

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN POTTAWATTAMIE...
SOUTHWESTERN HARRISON AND SOUTHEASTERN WASHINGTON COUNTIES THROUGH
215 AM CDT...

At 206 AM CDT, Doppler radar was tracking a strong thunderstorm 3
miles southwest of Missouri Valley, or 9 miles east of Blair, moving
southeast at 25 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down small tree branches and blow
         around unsecured objects. Minor hail damage to vegetation
         is possible.

Locations impacted include...
Missouri Valley, Fort Calhoun, Modale, Desoto Bend National Wildlife
Refuge, Wilson Island State Park, and Historical Village Welcome
Center.

This includes Interstate 29 between mile markers 68 and 79.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4145 9607 4162 9606 4161 9578 4144 9579
TIME...MOT...LOC 0706Z 294DEG 20KT 4153 9595

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

DeWald

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 2, 2:12 AM CDTSevere Thunderstorm WarningOAXWashington48 min
Aug 2, 6:14 AM CDTSevere Thunderstorm Warning Considerable damage threatOAXMadison, Pierce, Stanton, Thurston, Wayne31 min
Aug 2, 6:23 AM CDTFlash Flood WarningOAXBurt4 hr
Aug 2, 6:31 AM CDTSevere Thunderstorm WarningOAXBurt, Cuming, Stanton, Thurston, Wayne29 min
Aug 2, 6:33 AM CDTAreal Flood AdvisoryOAXBurt, Colfax, Cuming, Dodge, Stanton, Thurston and 1 more3 hr
Aug 2, 6:40 AM CDTSevere Thunderstorm Warning Considerable damage threatOAXThurston, Wayne35 min
Aug 2, 6:48 AM CDTAreal Flood AdvisoryOAXDodge101 min
Aug 2, 6:55 AM CDTSevere Thunderstorm WarningOAXBurt, Cuming, Thurston, Wayne39 min
Aug 2, 7:17 AM CDTFlash Flood Warning Considerable damage threatOAXBurt3 hr
Aug 2, 7:27 AM CDTFlash Flood WarningOAXBurt, Washington3 hr
Aug 2, 7:57 AM CDTAreal Flood AdvisoryOAXDouglas, Sarpy, Washington3 hr
Aug 2, 8:14 AM CDTAreal Flood AdvisoryOAXDodge, Douglas, Washington104 min
Aug 2, 10:20 AM CDTAreal Flood WarningOAXBurt, Dodge, Washington3 hr
Aug 2, 1:59 AM CDTSpecial Weather StatementOAXCass16 min
Aug 2, 2:04 AM CDTSpecial Weather StatementOAXPottawattamie11 min
Aug 2, 2:06 AM CDTSpecial Weather StatementOAXHarrison9 min
Aug 2, 2:26 AM CDTSevere Thunderstorm WarningOAXHarrison, Pottawattamie, Shelby37 min
Aug 2, 4:45 AM CDTFlash Flood WarningOAXHarrison, Shelby6 hr

Nearby

Flash Flood Warnings in Iowa, 2023Every flash flood warning in 2023

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.