Alert archive / Wyoming / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 92, NWS Cheyenne, WY

July 9, 2021Niobrara County, Wyoming; Sioux County, Nebraska

NWS Cheyenne, WY issued this severe thunderstorm warning at Jul 9, 2021, 8:04 PM MDT for Niobrara County, Wyoming; Sioux County, Nebraska. It was in force for 41 min. 3 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, 8:04 PM MDT (02:04 UTC)
Expired: Jul 9, 2021, 8:45 PM MDT
In force: 41 min
Issued by: NWS Cheyenne, WY
Area: Storm-based polygon
Hail: 1.75 in
Wind: 70.0 mph

Counties Sioux County, NE, Niobrara County, WY

The radar

The Rapid City radar (KUDX), 158 km from the middle of the area, began a volume at 02:07 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, 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.
Jul 9, 8:38 PM MDT	TSTM WND GST 61	13 Nnw Harrison, NE
Jul 9, 8:40 PM MDT	TSTM WND GST 63	Harrison, NE

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, 2.1 hours before the alert went out and 151 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.

535 
WUUS55 KCYS 100204
SVRCYS
NEC165-WYC027-100245-
/O.NEW.KCYS.SV.W.0092.210710T0204Z-210710T0245Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Cheyenne WY
804 PM MDT Fri Jul 9 2021

The National Weather Service in Cheyenne has issued a

* Severe Thunderstorm Warning for...
  Northwestern Sioux County in the Panhandle of Nebraska...
  Central Niobrara County in east central Wyoming...

* Until 845 PM MDT.

* At 804 PM MDT, a severe thunderstorm was located near Redbird, or
  24 miles southwest of Edgemont, moving southeast at 60 mph.

  HAZARD...Golf ball size 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...
  Harrison, Montrose, Redbird and Lance Creek. 

This replaces the Severe Thunderstorm Warning which was previously 
in effect for northern Niobrara County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare immediately for large hail and damaging winds. People outside
should move immediately to shelter inside a strong building. Stay
away from windows.

&&

LAT...LON 4300 10405 4300 10361 4295 10358 4259 10386
      4311 10473 4325 10471 4331 10405
TIME...MOT...LOC 0204Z 305DEG 50KT 4315 10428 

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

Hammer

2 follow-up statements

497 
WWUS55 KCYS 100216
SVSCYS

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

NEC165-WYC027-100245-
/O.CON.KCYS.SV.W.0092.000000T0000Z-210710T0245Z/
Sioux NE-Niobrara WY-
816 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 845 PM MDT
FOR NORTHWESTERN SIOUX AND EAST CENTRAL NIOBRARA COUNTIES...

At 815 PM MDT, a severe thunderstorm was located 13 miles south of
Redbird, or 24 miles northeast of Lusk, moving southeast at 55 mph.

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

SOURCE...Law enforcement. Ping Pong ball size hail was reported 
         along Highway 85 east of Lance Creek 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...
Harrison, Montrose and Redbird. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Prepare immediately for large hail and damaging winds. People outside
should move to a shelter, inside a strong building and away from
windows.

&&

LAT...LON 4300 10405 4300 10361 4295 10358 4259 10386
      4315 10464 4323 10460 4331 10405
TIME...MOT...LOC 0215Z 305DEG 48KT 4306 10419 

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

Hammer

715 
WWUS55 KCYS 100226
SVSCYS

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

NEC165-WYC027-100245-
/O.CON.KCYS.SV.W.0092.000000T0000Z-210710T0245Z/
Sioux NE-Niobrara WY-
826 PM MDT Fri Jul 9 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 845 PM MDT
FOR NORTHWESTERN SIOUX AND EAST CENTRAL NIOBRARA COUNTIES...

At 826 PM MDT, a severe thunderstorm was located 17 miles west of
Montrose, or 23 miles northeast of Lusk, moving southeast at 55 mph.

This is a very dangerous storm.

HAZARD...Baseball size hail and 70 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...People and animals outdoors will be severely injured. 
         Expect shattered windows, extensive damage to roofs, 
         siding, and vehicles.

Locations impacted include...
Harrison and Montrose. 

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 4300 10405 4300 10361 4295 10358 4259 10386
      4304 10448 4311 10406
TIME...MOT...LOC 0226Z 305DEG 49KT 4296 10407 

TORNADO...POSSIBLE
HAIL...2.75IN
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, 7:25 PM MDT	Severe Thunderstorm Warning	CYS	Niobrara	50 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
Jul 9, 6:07 PM MDT	Tornado Warning	CYS	Morrill	26 min
Jul 9, 8:47 PM MDT	Severe Thunderstorm Warning	CYS	Dawes	43 min
Jul 9, 9:01 PM MDT	Severe Thunderstorm Warning	CYS	Box Butte, Dawes, Sioux	44 min
Jul 9, 9:22 PM MDT	Severe Thunderstorm Warning	CYS	Box Butte, Dawes	38 min
Jul 9, 9:33 PM MDT	Severe Thunderstorm Warning	CYS	Box Butte, Dawes, Morrill, Sioux	57 min

Nearby

Severe Thunderstorm Warnings in Wyoming, 2021 Severe Thunderstorm Warnings in Nebraska, 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.