Alert archive / Wyoming / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 107, NWS Cheyenne, WY

July 20, 2020Converse County, Wyoming

NWS Cheyenne, WY issued this severe thunderstorm warning at Jul 20, 2020, 4:52 PM MDT for Converse County, Wyoming. It was in force for 18 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
Jul 20, 2020, 4:52 PM MDT (22:52 UTC)
Expired
Jul 20, 2020, 5:10 PM MDT
In force
18 min
Issued by
NWS Cheyenne, WY
Area
Storm-based polygon
Hail
1.0 in
Wind
60.0 mph

County Converse County, WY

The radar

The Cheyenne radar (KCYS), 210 km from the middle of the area, began a volume at 22:53 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

Rapid City, SD (KUNR), launched 12:00Z, 10.9 hours before the alert went out and 244 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, Rapid City, SD at 12:00Z on 2020-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 89 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, Rapid City, SD at 12:00Z on 2020-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 79 square meters per square second.193958Sfc1 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
89 J/kg
Mixed-layer CIN
-242 J/kg
Mixed-layer LCL
1354 m above ground
0-6 km bulk shear
35 kt
0-1 km storm-relative helicity
79 m²/s²
0-3 km storm-relative helicity
120 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0

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 Cheyenne, WY wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 20, 2:06 PM MDT, 2 hours 46 minutes earlier.

Area forecast discussion, Jul 20, 2:06 PM MDT, 2 hours 46 minutes before
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Hazardous weather outlook, Jul 20, 1:27 PM MDT, 3 hours 25 minutes before
Hazardous Weather Outlook
National Weather Service Cheyenne WY
127 PM MDT Mon Jul 20 2020

NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-118-119-
211930-
Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill-
Kimball County-Cheyenne-North Sioux-South Sioux-
Converse County Lower Elevations-Niobrara County-
East Platte County-Goshen County-Central Laramie County-
East Laramie County-
127 PM MDT Mon Jul 20 2020

This hazardous weather outlook is for portions of panhandle
Nebraska...western Nebraska...east central Wyoming and southeast
Wyoming.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Isolated to scattered strong to severe thunderstorms possible.
Damaging winds and large hail main threats in strongest storms.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Recurring chances for afternoon and evening strong to severe
thunderstorms this week. Damaging winds and large hail possible
threats in strongest storms.

.Spotter information statement...

Spotters are encouraged to report any hail and thunderstorm wind
damage to the Cheyenne, Wyoming National Weather Service.

WYZ103>106-109>117-211930-
North Laramie Range-Ferris/Seminoe/Shirley Mountains-
Shirley Basin-Central Laramie Range and Southwest Platte County-
Central Carbon County-North Snowy Range Foothills-
Southwest Carbon County-Sierra Madre Range-
Upper North Platte River Basin-Snowy Range-Laramie Valley-
South Laramie Range-South Laramie Range Foothills-
127 PM MDT Mon Jul 20 2020

This hazardous weather outlook is for portions of south central
Wyoming and southeast Wyoming.

.DAY ONE...THIS AFTERNOON AND TONIGHT

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Non-severe thunderstorms possible this week. Frequent lightning,
gusty winds, and small hail possible.

.Spotter information statement...

Spotter activation will not be needed.

In the hours before

Special weather statement, Jul 20, 1:27 PM MDT, 3 hours 25 minutes before
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Special weather statement, Jul 20, 2:27 PM MDT, 2 hours 25 minutes before
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Special weather statement, Jul 20, 2:53 PM MDT, 1 hour 59 minutes before
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Special weather statement, Jul 20, 3:45 PM MDT, 1 hour 7 minutes before
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Special weather statement, Jul 20, 4:26 PM MDT, 26 minutes before
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Special weather statement, Jul 20, 4:27 PM MDT, 25 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Jul 19, 6:02 PM MDTSevere Thunderstorm WarningCYSConverse, Niobrara58 min
Jul 19, 6:44 PM MDTTornado WarningCYSConverse, Niobrara31 min
Jul 19, 7:14 PM MDTSevere Thunderstorm WarningCYSConverse, Niobrara46 min
Jul 19, 7:24 PM MDTTornado WarningCYSNiobrara36 min
Jul 19, 7:57 PM MDTTornado WarningCYSNiobrara33 min
Jul 19, 8:03 PM MDTSevere Thunderstorm WarningCYSGoshen42 min
Jul 19, 8:14 PM MDTSevere Thunderstorm WarningCYSGoshen, Niobrara46 min
Jul 19, 8:30 PM MDTTornado WarningCYSGoshen, Niobrara17 min
Jul 19, 8:45 PM MDTSevere Thunderstorm WarningCYSGoshen, Niobrara45 min
Jul 19, 9:39 PM MDTSevere Thunderstorm WarningCYSGoshen51 min
Jul 20, 12:04 PM MDTSpecial Weather StatementCYSPlatte26 min
Jul 20, 12:51 PM MDTSpecial Weather StatementCYSPlatte24 min
Jul 20, 1:15 PM MDTSpecial Weather StatementCYSAlbany30 min
Jul 20, 1:27 PM MDTSpecial Weather StatementCYSNiobrara33 min
Jul 20, 2:27 PM MDTSpecial Weather StatementCYSNiobrara33 min
Jul 20, 2:53 PM MDTSpecial Weather StatementCYSConverse, Niobrara52 min
Jul 20, 3:45 PM MDTSpecial Weather StatementCYSConverse45 min
Jul 20, 4:27 PM MDTSpecial Weather StatementCYSConverse48 min
Jul 20, 5:05 PM MDTSpecial Weather StatementCYSPlatte40 min
Jul 20, 5:13 PM MDTSpecial Weather StatementCYSNiobrara47 min
Jul 20, 5:14 PM MDTSpecial Weather StatementCYSNiobrara46 min
Jul 20, 5:16 PM MDTSpecial Weather StatementCYSConverse44 min
Jul 20, 5:41 PM MDTSpecial Weather StatementCYSLaramie49 min
Jul 19, 6:32 PM MDTSevere Thunderstorm WarningCYSBox Butte, Dawes, Sioux58 min
Jul 19, 8:11 PM MDTSevere Thunderstorm WarningCYSBox Butte, Dawes49 min
Jul 19, 8:54 PM MDTSevere Thunderstorm WarningCYSBox Butte, Dawes38 min
Jul 19, 9:31 PM MDTSpecial Weather StatementCYSBox Butte44 min
Jul 19, 9:35 PM MDTSpecial Weather StatementCYSSioux40 min
Jul 20, 4:26 PM MDTSpecial Weather StatementCYSSioux49 min
Jul 20, 4:56 PM MDTSpecial Weather StatementCYSSioux49 min
Jul 20, 5:39 PM MDTSpecial Weather StatementCYSBox Butte51 min

Nearby

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