Alert archive / Iowa / Special Weather Statements in 2020

Special Weather Statement, NWS Des Moines, IA

August 6, 2020Polk County, Iowa

NWS Des Moines, IA issued this special weather statement at Aug 6, 2020, 4:15 PM CDT for Polk County, Iowa. It was in force for 45 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 6, 2020, 4:15 PM CDT (21:15 UTC)
Expired
Aug 6, 2020, 5:00 PM CDT
In force
45 min
Issued by
NWS Des Moines, IA

County Polk County, IA

The radar

The Des Moines radar (KDMX), 12 km from the middle of the area, began a volume at 21:17 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 12:00Z, 9.3 hours before the alert went out and 234 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 12:00Z on 2020-08-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 284 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 12:00Z on 2020-08-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 161 square meters per square second.19395878Sfc1 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
284 J/kg
Mixed-layer CIN
-289 J/kg
Mixed-layer LCL
1016 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
161 m²/s²
0-3 km storm-relative helicity
268 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

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

NWS Des Moines, IA wrote its last area forecast discussion before this special weather statement went out at Aug 6, 3:46 PM CDT, 29 minutes earlier.

Area forecast discussion, Aug 6, 3:46 PM CDT, 29 minutes before
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Hazardous weather outlook, Aug 6, 3:24 PM CDT, 51 minutes before
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In the hours before

Special weather statement, Aug 6, 12:00 PM CDT, 4 hours 15 minutes before
Special Weather Statement
National Weather Service Des Moines IA
1200 PM CDT Thu Aug 6 2020

IAZ046-047-059-061745-
Boone IA-Greene IA-Dallas IA-
1200 PM CDT Thu Aug 6 2020

...Dime to Penny Hail and Winds to 40 mph Possible...

At 1159 AM CDT, Doppler radar was tracking a strong thunderstorm near
Perry, moving east at 25 mph.

Penny size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Perry, Woodward, Minburn, Rippey, Dawson, Bouton, Berkley, Perry
Municipal Airport and Ledges State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4201 9389 4171 9385 4178 9428 4195 9429
TIME...MOT...LOC 1659Z 261DEG 23KT 4189 9420

Kotenberg
Special weather statement, Aug 6, 1:01 PM CDT, 3 hours 14 minutes before
Special Weather Statement
National Weather Service Des Moines IA
101 PM CDT Thu Aug 6 2020

IAZ072-061830-
Madison IA-
101 PM CDT Thu Aug 6 2020

...Dime to Penny Size Hail Possible...

At 101 PM CDT, Doppler radar was tracking a strong thunderstorm near
Winterset, moving east at 15 mph.

Penny size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Avenue Of The Saints Event Center, St. Charles, Patterson, Bevington
and Badger Creek State Park.

LAT...LON 4136 9398 4149 9397 4146 9379 4128 9379
TIME...MOT...LOC 1801Z 282DEG 12KT 4137 9392

Kotenberg
Local storm report, Aug 6, 1:06 PM CDT, 3 hours 9 minutes before
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Special weather statement, Aug 6, 2:05 PM CDT, 2 hours 10 minutes before
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Special weather statement, Aug 6, 3:21 PM CDT, 54 minutes before
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Special weather statement, Aug 6, 4:15 PM CDT, 0 minutes before
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The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 6, 10:57 AM CDTSpecial Weather StatementDMXGuthrie48 min
Aug 6, 11:00 AM CDTSpecial Weather StatementDMXDallas45 min
Aug 6, 11:11 AM CDTSevere Thunderstorm WarningDMXCarroll, Greene, Guthrie32 min
Aug 6, 12:00 PM CDTSpecial Weather StatementDMXDallas45 min
Aug 6, 1:01 PM CDTSpecial Weather StatementDMXMadison29 min
Aug 6, 2:05 PM CDTSpecial Weather StatementDMXGreene25 min
Aug 6, 3:21 PM CDTSpecial Weather StatementDMXBoone24 min
Aug 6, 3:35 PM CDTSevere Thunderstorm WarningDMXBoone, Dallas, Polk, Story40 min

Nearby

Special Weather Statements in Iowa, 2020Every special weather statement in 2020

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.