Alert archive / Iowa / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 51, NWS Quad Cities, IA

May 23, 2020Keokuk County, Washington County, Iowa

NWS Quad Cities, IA issued this severe thunderstorm warning at May 23, 2020, 6:29 AM CDT for Keokuk County, Washington County, Iowa. It was in force for 31 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: May 23, 2020, 6:29 AM CDT (11:29 UTC)
Expired: May 23, 2020, 7:00 AM CDT
In force: 31 min
Issued by: NWS Quad Cities, IA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 50.0 mph

Counties Keokuk County, IA, Washington County, IA

The radar

The Quad Cities radar (KDVN), 118 km from the middle of the area, began a volume at 11:35 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, 11.5 hours before the alert went out and 369 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 154 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 757 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 137 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

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 Quad Cities, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at May 23, 3:48 AM CDT, 2 hours 41 minutes earlier.

Area forecast discussion, May 23, 3:48 AM CDT, 2 hours 41 minutes before

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Hazardous weather outlook, May 23, 4:41 AM CDT, 1 hour 48 minutes before

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
441 AM CDT Sat May 23 2020

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-240945-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
441 AM CDT Sat May 23 2020

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...TODAY AND TONIGHT

Scattered thunderstorms are expected today. A few storms could
become severe. The main severe risk area is north of a line
from Cedar Rapids, Iowa to Monmouth, Illinois between Noon and
5 PM, as a warm front lifts northward across the area. A few
supercell thunderstorms will be possible accompanied by a threat
of large hail, damaging winds and tornadoes.

Patchy dense fog is possible overnight, mainly north of Interstate
80.

Portions of the Rock River is experiencing flooding. Please see
the latest Flood Statements and Flood Warnings for details.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

Thunderstorms will be possible late Sunday afternoon and evening in
Iowa. Some storms may become severe, with large hail and damaging
wind the primary threats.

There is a daily chance for thunderstorms Monday through
Wednesday. It is too early to determine the severe weather threat.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed for portions of the outlook
area this afternoon.

In the hours before

Special weather statement, May 23, 5:08 AM CDT, 1 hour 21 minutes before

Special Weather Statement
National Weather Service Quad Cities IA/IL
508 AM CDT Sat May 23 2020

IAC107-231045-
Keokuk-
508 AM CDT Sat May 23 2020

...A STRONG THUNDERSTORM WILL AFFECT KEOKUK COUNTY UNTIL 545 AM
CDT...

At 507 AM CDT, a strong thunderstorm was located near Ottumwa
Industrial Airport, or 7 miles north of Ottumwa, moving northeast at
30 mph.

Half inch hail is possible with this storm.

Locations impacted include...
Sigourney, Hedrick, What Cheer, Delta, Keswick, South English,
Martinsburg, Hayesville, Webster, Thornburg, Gibson, Lancaster, Coal
Creek, Keokuk County Expo, Lake Belva Deer Park, Yenruogis County
Park and Keokuk County Fairgrounds.

LAT...LON 4151 9241 4151 9224 4145 9202 4116 9222
      4116 9241
TIME...MOT...LOC 1007Z 203DEG 26KT 4112 9239

Gross

Special weather statement, May 23, 5:46 AM CDT, 43 minutes before

Special Weather Statement
National Weather Service Quad Cities IA/IL
546 AM CDT Sat May 23 2020

IAC011-095-101-107-177-183-231115-
Van Buren-Keokuk-Benton-Washington-Jefferson-Iowa-
546 AM CDT Sat May 23 2020

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN VAN
BUREN...KEOKUK...SOUTHWESTERN BENTON...WESTERN WASHINGTON...WESTERN
JEFFERSON AND IOWA COUNTIES UNTIL 615 AM CDT...

At 544 AM CDT, radar indicated strong thunderstorms were located
along a line extending from 8 miles east of Montezuma to near
Martinsburg to near Douds. Movement was north at 30 mph.

Half inch hail is possible with these storms.

These storms will be near...
  Sigourney and Victor around 605 AM CDT.
  Fairfield, Ladora, Maharishi Vedic City and Abingdon around 610 AM
  CDT.
  Belle Plaine, Richland, South English, Harper, Luzerne and
  Pleasant Plain around 615 AM CDT.

Other locations impacted by these storms include Ollie, Fairfield
Municipal Airport, Perlee, Linby, Lancaster, Lake Iowa Park, Keokuk
County Expo, Pekin, Jefferson County Fairgrounds and Lake Belva Deer
Park.

This includes Interstate 80 in Iowa between mile markers 205 and 219.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4151 9230 4153 9230 4205 9229 4160 9194
      4115 9184 4081 9208 4102 9218 4116 9218
      4116 9224 4151 9238
TIME...MOT...LOC 1044Z 199DEG 27KT 4159 9235 4117 9219 4089 9209

Gross

Special weather statement, May 23, 6:22 AM CDT, 7 minutes before

Special Weather Statement
National Weather Service Quad Cities IA/IL
622 AM CDT Sat May 23 2020

IAC095-101-107-183-231145-
Keokuk-Washington-Jefferson-Iowa-
622 AM CDT Sat May 23 2020

...A STRONG THUNDERSTORM WILL AFFECT EASTERN KEOKUK...WESTERN
WASHINGTON...NORTH CENTRAL JEFFERSON AND SOUTHERN IOWA COUNTIES UNTIL
645 AM CDT...

At 622 AM CDT, a strong thunderstorm was located over Richland, or 13
miles southeast of Sigourney, moving northeast at 30 mph.

Nickel size hail is possible with this storm.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4111 9192 4120 9213 4156 9194 4142 9162
TIME...MOT...LOC 1122Z 208DEG 26KT 4122 9198

Gross

The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 23, 5:08 AM CDT	Special Weather Statement	DVN	Keokuk	37 min
May 23, 5:46 AM CDT	Special Weather Statement	DVN	Iowa, Jefferson, Keokuk	29 min
May 23, 6:22 AM CDT	Special Weather Statement	DVN	Washington	23 min
May 23, 9:11 AM CDT	Special Weather Statement	DVN	Linn	34 min
May 23, 9:23 AM CDT	Special Weather Statement	DVN	Cedar	37 min
May 23, 10:02 AM CDT	Special Weather Statement	DVN	Scott	28 min
May 23, 12:18 PM CDT	Tornado Warning	DVN	Cedar, Johnson	42 min
May 23, 12:39 PM CDT	Tornado Warning	DVN	Cedar, Clinton	51 min
May 23, 12:50 PM CDT	Tornado Warning Tornado observed	DVN	Cedar, Jones	40 min
May 23, 12:59 PM CDT	Tornado Warning	DVN	Scott	46 min
May 23, 1:17 PM CDT	Tornado Warning	DVN	Clinton, Jackson	43 min
May 23, 1:18 PM CDT	Tornado Warning Tornado observed	DVN	Cedar, Jones	18 min
May 23, 1:29 PM CDT	Tornado Warning	DVN	Jones	16 min
May 23, 1:54 PM CDT	Tornado Warning	DVN	Jackson	38 min
May 23, 2:27 PM CDT	Tornado Warning Tornado observed	DVN	Jackson	34 min
May 23, 10:28 AM CDT	Severe Thunderstorm Warning	DVN	Henry, Mercer, Rock Island	25 min
May 23, 11:21 AM CDT	Special Weather Statement	DVN	Henry	24 min
May 23, 11:37 AM CDT	Special Weather Statement	DVN	Whiteside	38 min
May 23, 12:13 PM CDT	Severe Thunderstorm Warning	DVN	Carroll, Whiteside	62 min
May 23, 1:18 PM CDT	Severe Thunderstorm Warning	DVN	Bureau, Putnam	27 min
May 23, 1:40 PM CDT	Tornado Warning	DVN	Carroll, Whiteside	5 min
May 23, 1:50 PM CDT	Severe Thunderstorm Warning	DVN	Carroll, Whiteside	55 min
May 23, 2:17 PM CDT	Tornado Warning	DVN	Bureau, Henry, Whiteside	23 min
May 23, 2:27 PM CDT	Tornado Warning	DVN	Carroll, Whiteside	36 min
May 23, 3:05 PM CDT	Tornado Warning	DVN	Jo Daviess	27 min
May 23, 4:02 PM CDT	Severe Thunderstorm Warning	DVN	Carroll, Jo Daviess, Stephenson	58 min
May 23, 4:19 PM CDT	Tornado Warning Tornado observed	DVN	Jo Daviess	11 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2020 Every 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.