Alert archive / Wyoming / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 91, NWS Cheyenne, WY

July 9, 2021Niobrara County, Wyoming

NWS Cheyenne, WY issued this severe thunderstorm warning at Jul 9, 2021, 7:25 PM MDT for Niobrara County, Wyoming. It was in force for 50 min. 2 reports 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: Jul 9, 2021, 7:25 PM MDT (01:25 UTC)
Expired: Jul 9, 2021, 8:15 PM MDT
In force: 50 min
Issued by: NWS Cheyenne, WY
Area: Storm-based polygon
Tornado: Possible
Hail: 2.0 in
Wind: 70.0 mph

County Niobrara County, WY

The radar

The Rapid City radar (KUDX), 156 km from the middle of the area, began a volume at 01:26 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

Time	Report	Where	Remark
Jul 9, 7:40 PM MDT	HAIL 1.75	15 W Mule Creek Junctio, WY
Jul 9, 8:06 PM MDT	HAIL 1.5	9 Ssw Redbird, WY	COUNTY OFFICIALS REPORTED PING PONG BALL SIZED HAIL AND WIND GUSTS AROUND 40 MPH.

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

The watch it was issued in

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

Issued	Product	Office	Lasted
Jul 9, 2:16 PM MDT	Severe Thunderstorm Watch	SPC	9 hr

The nearest sounding before it

Rapid City, SD (KUNR), launched 00:00Z, 1.4 hours before the alert went out and 149 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: 240 J/kg
Mixed-layer CIN: -260 J/kg
Mixed-layer LCL: 2327 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: -35 m²/s²
0-3 km storm-relative helicity: 76 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

835 
WUUS55 KCYS 100125
SVRCYS
WYC027-100215-
/O.NEW.KCYS.SV.W.0091.210710T0125Z-210710T0215Z/

BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Cheyenne WY
725 PM MDT Fri Jul 9 2021

The National Weather Service in Cheyenne has issued a

* Severe Thunderstorm Warning for...
  Northern Niobrara County in east central Wyoming...

* Until 815 PM MDT.

* At 725 PM MDT, a severe thunderstorm was located near Clareton, or
  29 miles southwest of Newcastle, moving southeast at 60 mph.

  HAZARD...Two inch hail and 70 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...People and animals outdoors will be injured. Expect hail 
           damage to roofs, siding, windows, and vehicles. Expect 
           considerable tree damage. Wind damage is also likely to 
           mobile homes, roofs, and outbuildings.

* Locations impacted include...
  Mule Creek Junction and Redbird. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This thunderstorm is capable of producing all types of severe weather
including extremely large hail, destructive straight line winds and
tornadoes. Move quickly to a safe shelter such as an interior room, a
bathroom, closet or basement.

&&

LAT...LON 4323 10405 4303 10443 4330 10489 4350 10490
      4350 10406
TIME...MOT...LOC 0125Z 306DEG 51KT 4362 10469 

TORNADO...POSSIBLE
HAIL...2.00IN
WIND...70MPH
 
$$

Hammer

3 follow-up statements

080 
WWUS55 KCYS 100142
SVSCYS

Severe Weather Statement
National Weather Service Cheyenne WY
742 PM MDT Fri Jul 9 2021

WYC027-100215-
/O.CON.KCYS.SV.W.0091.000000T0000Z-210710T0215Z/
Niobrara WY-
742 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM MDT
FOR NORTHERN NIOBRARA COUNTY...

At 742 PM MDT, a severe thunderstorm was located 13 miles southwest
of Morrisey, or 36 miles west of Edgemont, moving southeast at 60
mph.

HAZARD...Two inch hail and 70 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect 
         considerable tree damage. Wind damage is also likely to 
         mobile homes, roofs, and outbuildings.

Locations impacted include...
Mule Creek Junction and Redbird. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This thunderstorm is capable of producing all types of severe weather
including extremely large hail, destructive straight line winds and
tornadoes. Move quickly to a safe shelter, such as an interior room,
a bathroom or closet or basement.

&&

LAT...LON 4323 10405 4303 10443 4330 10489 4350 10478
      4350 10406
TIME...MOT...LOC 0142Z 300DEG 51KT 4337 10454 

TORNADO...POSSIBLE
HAIL...2.00IN
WIND...70MPH
 
$$

Hammer

897 
WWUS55 KCYS 100147
SVSCYS

Severe Weather Statement
National Weather Service Cheyenne WY
747 PM MDT Fri Jul 9 2021

WYC027-100215-
/O.CON.KCYS.SV.W.0091.000000T0000Z-210710T0215Z/
Niobrara WY-
747 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM MDT
FOR NORTHERN NIOBRARA COUNTY...

At 746 PM MDT, a severe thunderstorm was located 11 miles northwest
of Redbird, or 32 miles west of Edgemont, moving southeast at 60 mph.

HAZARD...Two inch hail and 70 mph wind gusts.

SOURCE...Trained weather spotters. Golf ball sized hail has been 
         reported 15 miles west of Mule Creek Junction with this 
         storm. 

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect 
         considerable tree damage. Wind damage is also likely to 
         mobile homes, roofs, and outbuildings.

Locations impacted include...
Mule Creek Junction and Redbird. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This thunderstorm is capable of producing all types of severe weather
including extremely large hail, destructive straight line winds and
tornadoes. Move quickly to a safe shelter, such as an interior room,
a bathroom or closet or basement.

&&

LAT...LON 4323 10405 4303 10443 4330 10489 4350 10478
      4350 10406
TIME...MOT...LOC 0146Z 306DEG 51KT 4333 10447 

TORNADO...POSSIBLE
HAIL...2.00IN
WIND...70MPH
 
$$

Hammer

662 
WWUS55 KCYS 100159
SVSCYS

Severe Weather Statement
National Weather Service Cheyenne WY
759 PM MDT Fri Jul 9 2021

WYC027-100215-
/O.CON.KCYS.SV.W.0091.000000T0000Z-210710T0215Z/
Niobrara WY-
759 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 815 PM MDT
FOR NORTHERN NIOBRARA COUNTY...

At 759 PM MDT, a severe thunderstorm was located over Redbird, or 24
miles west of Edgemont, moving southeast at 55 mph.

HAZARD...Golf ball size hail and 70 mph wind gusts.

SOURCE...Trained weather spotters. This storm has a history of 
         producing hail up to golf ball size.

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect 
         considerable tree damage. Wind damage is also likely to 
         mobile homes, roofs, and outbuildings.

Locations impacted include...
Mule Creek Junction and Redbird. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This thunderstorm is capable of producing all types of severe weather
including extremely large hail, destructive straight line winds and
tornadoes. Move quickly to a safe shelter, such as an interior room,
a bathroom or closet or basement.

&&

LAT...LON 4323 10405 4303 10443 4330 10489 4334 10457
      4350 10449 4350 10406
TIME...MOT...LOC 0159Z 305DEG 50KT 4323 10431 

TORNADO...POSSIBLE
HAIL...1.75IN
WIND...70MPH
 
$$

Hammer

The office that day

Everything else NWS Cheyenne, WY issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 9, 8:04 PM MDT	Severe Thunderstorm Warning	CYS	Niobrara	41 min
Jul 9, 8:31 PM MDT	Tornado Warning	CYS	Niobrara	44 min
Jul 9, 9:47 PM MDT	Special Weather Statement	CYS	Platte	28 min
Jul 9, 10:19 PM MDT	Severe Thunderstorm Warning	CYS	Goshen, Platte	41 min
Jul 9, 10:58 PM MDT	Special Weather Statement	CYS	Goshen	32 min

Nearby

Severe Thunderstorm Warnings in Wyoming, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.