Alert archive / Iowa / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 167, NWS Des Moines, IA

October 11, 20204 counties in Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Oct 11, 2020, 11:01 PM CDT for 4 counties in Iowa. It was in force for 59 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Oct 11, 2020, 11:01 PM CDT (04:01 UTC)
Expired
Oct 12, 2020, 12:00 AM CDT
In force
59 min
Issued by
NWS Des Moines, IA
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

Counties Adair County, IA, Adams County, IA, Cass County, IA, Taylor County, IA

The radar

The Des Moines radar (KDMX), 127 km from the middle of the area, began a volume at 04:04 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.

What was reported inside it

TimeReportWhereRemark
Oct 12, 12:10 AM CDTTSTM WND GST 61Bedford, IARWIS.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
Oct 11, 4:54 PM CDTSevere Thunderstorm WatchSPC8 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 4.0 hours before the alert went out and 133 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 2020-10-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 550 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 2020-10-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 240 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
550 J/kg
Mixed-layer CIN
-165 J/kg
Mixed-layer LCL
2135 m above ground
0-6 km bulk shear
51 kt
0-1 km storm-relative helicity
240 m²/s²
0-3 km storm-relative helicity
319 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.6

Open this sounding in Storm Lab

The text

As transmitted.

873 
WUUS53 KDMX 120401
SVRDMX
IAC001-003-029-173-120500-
/O.NEW.KDMX.SV.W.0167.201012T0401Z-201012T0500Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines, IA
Issued by National Weather Service Quad Cities IA/IL
1101 PM CDT Sun Oct 11 2020

The National Weather Service in Des Moines has issued a

* Severe Thunderstorm Warning for...
  Cass County in southwestern Iowa...
  Adams County in southwestern Iowa...
  Taylor County in southwestern Iowa...
  Southwestern Adair County in southwestern Iowa...

* Until midnight CDT.

* At 1101 PM CDT, severe thunderstorms were located along a line
  extending from near Griswold to 8 miles south of Farragut, moving
  east at 45 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Atlantic, Greenfield, Corning, Bedford, Lenox, Griswold, Lake
  Icaria, Fontanelle, Lewis, New Market, Clearfield, Massena,
  Cumberland, Prescott, Blockton, Gravity, Bridgewater, Nodaway,
  Cromwell and Sharpsburg.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4058 9491 4116 9493 4116 9516 4144 9515
      4130 9446 4057 9447
TIME...MOT...LOC 0401Z 268DEG 39KT 4121 9511 4060 9544 

HAIL...<.75IN
WIND...60MPH
 
$$

Uttech
3 follow-up statements
355 
WWUS53 KDMX 120416
SVSDMX

Severe Weather Statement
National Weather Service Des Moines, IA
Issued by National Weather Service Quad Cities IA/IL
1116 PM CDT Sun Oct 11 2020

IAC001-003-029-173-120500-
/O.CON.KDMX.SV.W.0167.000000T0000Z-201012T0500Z/
Cass IA-Adams IA-Taylor IA-Adair IA-
1116 PM CDT Sun Oct 11 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CDT
FOR CASS...ADAMS...TAYLOR AND SOUTHWESTERN ADAIR COUNTIES...

At 1115 PM CDT, severe thunderstorms were located along a line
extending from near Atlantic to near Blanchard, moving east at 50
mph.

HAZARD...60 mph wind gusts.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Atlantic, Greenfield, Corning, Bedford, Lenox, Griswold, Lake Icaria,
Fontanelle, Lewis, New Market, Clearfield, Massena, Cumberland,
Prescott, Blockton, Gravity, Bridgewater, Nodaway, Cromwell and
Sharpsburg.

LAT...LON 4058 9491 4116 9493 4116 9516 4144 9515
      4130 9446 4057 9447
TIME...MOT...LOC 0415Z 271DEG 43KT 4139 9495 4060 9530 

HAIL...<.75IN
WIND...60MPH
 
$$

Uttech
472 
WWUS53 KDMX 120437
SVSDMX

Severe Weather Statement
National Weather Service Des Moines, IA
Issued by National Weather Service Quad Cities IA/IL
1137 PM CDT Sun Oct 11 2020

IAC001-003-029-173-120500-
/O.CON.KDMX.SV.W.0167.000000T0000Z-201012T0500Z/
Cass IA-Adams IA-Taylor IA-Adair IA-
1137 PM CDT Sun Oct 11 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CDT
FOR CASS...ADAMS...TAYLOR AND SOUTHWESTERN ADAIR COUNTIES...

At 1137 PM CDT, severe thunderstorms were located along a line
extending from 7 miles northwest of Greenfield to near Hopkins,
moving east at 50 mph.

HAZARD...60 mph wind gusts.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Atlantic, Greenfield, Corning, Bedford, Lenox, Griswold, Lake Icaria,
Fontanelle, Lewis, New Market, Clearfield, Massena, Cumberland,
Prescott, Blockton, Gravity, Bridgewater, Nodaway, Cromwell and
Sharpsburg.

LAT...LON 4058 9491 4116 9493 4116 9516 4144 9515
      4130 9446 4057 9447
TIME...MOT...LOC 0437Z 270DEG 44KT 4138 9456 4057 9488 

HAIL...<.75IN
WIND...60MPH
 
$$

Uttech
153 
WWUS53 KDMX 120454
SVSDMX

Severe Weather Statement
National Weather Service Des Moines, IA
Issued by National Weather Service Quad Cities IA/IL
1154 PM CDT Sun Oct 11 2020

IAC001-003-029-173-120500-
/O.CON.KDMX.SV.W.0167.000000T0000Z-201012T0500Z/
Cass IA-Adams IA-Taylor IA-Adair IA-
1154 PM CDT Sun Oct 11 2020

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CDT
FOR SOUTHEASTERN CASS...ADAMS...TAYLOR AND SOUTHWESTERN ADAIR
COUNTIES...

At 1154 PM CDT, severe thunderstorms were located along a line
extending from 7 miles south of Stuart to near Athelstan, moving east
at 45 mph.

HAZARD...60 mph wind gusts.

SOURCE...Trained weather spotters.

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

Locations impacted include...
Greenfield, Corning, Bedford, Lenox, Lake Icaria, Fontanelle, New
Market, Clearfield, Massena, Cumberland, Prescott, Blockton, Gravity,
Bridgewater, Nodaway, Cromwell, Sharpsburg, Kent, Conway and Carbon.

LAT...LON 4058 9491 4116 9493 4134 9488 4130 9446
      4057 9447
TIME...MOT...LOC 0454Z 268DEG 39KT 4139 9432 4058 9464 

HAIL...<.75IN
WIND...60MPH
 
$$

Uttech

What forecasters said that day

The local office's own words before this severe thunderstorm warning 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 severe thunderstorm warning went out at Oct 11, 6:24 PM CDT, 4 hours 37 minutes earlier.

Area forecast discussion, Oct 11, 6:24 PM CDT, 4 hours 37 minutes before
AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
Issued by National Weather Service Quad Cities IA IL
624 PM CDT Sun Oct 11 2020

...AVIATION UPDATE...

.Discussion...
A rather wild ride from a very warm windy day today to a cooler
pleasant day tomorrow is expected tonight. In the short term, the
wind is certainly the story, as wind gusts continue to reach near
advisory levels in the northwestern counties, while 15 to 25 mph
are more common in the east. This wind will decrease with the loss
of mixing depth by early evening/sunset, which will begin the
reduction in the over all severe weather shear profile.

Tonight, the cold front will arrive in the far west around 8 PM
and exit far east around 4 AM. That will be the advertised severe
weather time frame, but certainly the available DCAPE and low
level shear interaction for any storm to interact with will be
mainly in the far northwest with a general decay in storm
intensity the farther east and late into the night we go. Thus,
this is more of a "can't rule out" severe weather night, than one
capable of becoming a widespread wind producer. Still, wind gusts
to 40-50 mph see very much possible with evening storms, and
overnight, some gusts to 45 mph still be possible, given the
strong winds aloft.

Rainfall tonight, should be in the quarter to half inch range for
locations northwest of a Fort Dodge to Mason City line, and up to
a quarter inch southeast of that axis.

Looking at Monday through Wednesday, very pleasant conditions are
expected with dry air, and highs reaching the upper 60s to mid
70s.

A strong cold front will arrive late Wednesday, with a pattern
change toward much cooler weather to finish the week. A deep and
broad upper trof is forecast over the Great Lakes, with highs in
the 50s, and lows in the upper 20s to mid 30s. This pattern is
likely to bring a killing freeze to much of the Upper Midwest if
they haven't seen it yet.

ERVIN

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1223 PM CDT Sun Oct 11 2020

A breezy south to southeast wind at 15 to 25 kts, gusting to 30
kts at times will continue into the early evening, with VFR/clear
to partly cloudy conditions. A cold front with thunderstorms will
arrive in the 03-05Z time frame and bring a 1-2 hour period of
rain and gusty winds, with some threat of lightning.

This front will bring a line of showers and thunderstorms east
across Iowa, with a period of MVFR/brief IFR weather with it. A
quick wind change to west to northwest will occur, and following
the rain, a period of strong northwest winds are expected which
will see gusts over 25 kts. By 10-12Z Monday, winds will decrease
somewhat and VFR weather should extend through the day Monday.

ERVIN

&&

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

DISCUSSION...Ervin
AVIATION...Ervin
Hazardous weather outlook, Oct 11, 4:36 AM CDT, 18 hours 25 minutes before
Hazardous Weather Outlook
National Weather Service Des Moines IA
Issued by National Weather Service Quad Cities IA IL
436 AM CDT Sun Oct 11 2020

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-120945-
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-
436 AM CDT Sun Oct 11 2020

This Hazardous Weather Outlook is for portions of central Iowa,
north central Iowa, northeast Iowa, northwest Iowa, south central
Iowa, southeast Iowa, southwest Iowa, and west central Iowa.

.DAY ONE...Today and Tonight

A line of thunderstorms will move across Iowa this evening and
overnight. The primary threat is damaging winds, mainly along
and west of Interstate 35 where the Storm Prediction Center has
placed a slight risk for severe weather. The storms are
anticipated to weaken overnight as they move east of Interstate
35, where a marginal risk for severe weather exists.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight.

The office that day

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

IssuedProductOfficeCountiesLasted
Oct 11, 11:52 PM CDTSevere Thunderstorm WarningDMXAdair, Clarke, Decatur, Madison, Ringgold, Union and 1 more53 min
Oct 12, 12:00 AM CDTSevere Thunderstorm WarningDMXAdams, Taylor15 min
Oct 12, 12:12 AM CDTSpecial Weather StatementDMXCalhoun, Carroll, Greene, Humboldt, Pocahontas, Webster48 min
Oct 12, 12:21 AM CDTSpecial Weather StatementDMXBoone, Polk, Story, Warren54 min
Oct 12, 12:46 AM CDTSpecial Weather StatementDMXClarke, Decatur, Lucas44 min
Oct 12, 1:31 AM CDTSpecial Weather StatementDMXCerro Gordo, Franklin, Hardin59 min
Oct 12, 2:11 AM CDTSevere Thunderstorm WarningDMXCerro Gordo, Hancock, Winnebago, Worth49 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2020Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.