Alert archive / Nebraska / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 305

June 22, 202110 counties in Iowa; 20 counties in Nebraska

The Storm Prediction Center issued this severe thunderstorm watch at Jun 22, 2021, 4:49 PM CDT for 10 counties in Iowa; 20 counties in Nebraska. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Jun 22, 2021, 4:49 PM CDT (21:49 UTC)
Expired
Jun 22, 2021, 9:00 PM CDT
In force
4 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt
All 30 counties

Adair County, IA, Audubon County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Greene County, IA, Guthrie County, IA, Harrison County, IA, Monona County, IA, Shelby County, IA, Antelope County, NE, Boone County, NE, Burt County, NE, Butler County, NE, Colfax County, NE, Cuming County, NE, Dodge County, NE, Greeley County, NE, Howard County, NE, Madison County, NE, Merrick County, NE, Nance County, NE, Pierce County, NE, Platte County, NE, Polk County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE, Wayne County, NE, York County, NE

The radar

The Omaha radar (KOAX), 62 km from the middle of the area, began a volume at 21:50 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 SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
10%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
30%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
50%

Warnings issued inside it

17 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jun 22, 5:14 PM CDTSevere Thunderstorm WarningOAXAntelope, Madison, Pierce46 min
Jun 22, 5:42 PM CDTSevere Thunderstorm WarningOAXMadison48 min
Jun 22, 6:09 PM CDTSevere Thunderstorm WarningDMXBoone, Calhoun, Carroll, Greene, Webster51 min
Jun 22, 6:09 PM CDTSevere Thunderstorm WarningOAXAntelope36 min
Jun 22, 6:26 PM CDTSevere Thunderstorm WarningOAXBoone, Platte16 min
Jun 22, 6:28 PM CDTSevere Thunderstorm WarningOAXMadison, Platte32 min
Jun 22, 6:33 PM CDTSevere Thunderstorm WarningDMXCarroll, Greene42 min
Jun 22, 6:49 PM CDTSevere Thunderstorm WarningDMXDallas, Guthrie41 min
Jun 22, 6:53 PM CDTSevere Thunderstorm WarningOAXAntelope, Boone, Madison, Platte18 min
Jun 22, 6:58 PM CDTSevere Thunderstorm WarningOAXPlatte32 min
Jun 22, 6:59 PM CDTSevere Thunderstorm WarningGIDMerrick, Nance31 min
Jun 22, 7:17 PM CDTSevere Thunderstorm WarningOAXPlatte28 min
Jun 22, 7:28 PM CDTSevere Thunderstorm WarningGIDMerrick, Nance, Polk47 min
Jun 22, 7:28 PM CDTSevere Thunderstorm WarningOAXPlatte19 min
Jun 22, 7:41 PM CDTSevere Thunderstorm WarningOAXPlatte15 min
Jun 22, 7:59 PM CDTSevere Thunderstorm WarningGIDMerrick, Polk, York46 min
Jun 22, 8:42 PM CDTSevere Thunderstorm WarningGIDYork33 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 9.8 hours before the alert went out and 62 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 2021-06-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 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 2021-06-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 259 square meters per square second.1939587897Sfc1 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
1 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1910 m above ground
0-6 km bulk shear
59 kt
0-1 km storm-relative helicity
259 m²/s²
0-3 km storm-relative helicity
324 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

415 
WWUS20 KWNS 222146
SEL5  
SPC WW 222146
IAZ000-NEZ000-230200-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 305
NWS Storm Prediction Center Norman OK
450 PM CDT Tue Jun 22 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  West-central Iowa
  East-central Nebraska

* Effective this Tuesday afternoon and evening from 450 PM until
  900 PM CDT.

* Primary threats include...
  Isolated very large hail events to 2 inches in diameter possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...A couple supercells might evolve south-southeast out of a
storm cluster across northeast Nebraska through about sunset.

The severe thunderstorm watch area is approximately along and 40
statute miles north and south of a line from 40 miles north
northwest of Grand Island NE to 55 miles east southeast of Denison
IA. For a complete depiction of the watch see the associated watch
outline update (WOUS64 KWNS WOU5).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
33030.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jun 22, 3:41 PM CDTMesoscale DiscussionSPCAdair, Adams, Audubon, Boone, Buena Vista, Calhoun and 34 more2 hr
Jun 22, 6:51 PM CDTMesoscale DiscussionSPCAdair, Adams, Appanoose, Audubon, Boone, Calhoun and 36 more54 min

Nearby

Severe Thunderstorm Watches in Nebraska, 2021Severe Thunderstorm Watches in Iowa, 2021Every severe thunderstorm watch in 2021

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.