Alert archive / Wyoming / Severe Thunderstorm Warnings in 2025

Severe Thunderstorm Warning 5, NWS Riverton, WY

May 11, 2025Park County, Wyoming

NWS Riverton, WY issued this severe thunderstorm warning at May 11, 2025, 5:29 PM MDT for Park County, Wyoming. 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 11, 2025, 5:29 PM MDT (23:29 UTC)
Expired
May 11, 2025, 6:00 PM MDT
In force
31 min
Issued by
NWS Riverton, WY
Area
Storm-based polygon
Hail
0.75 in
Wind
60.0 mph

County Park County, WY

The radar

The Billings radar (KBLX), 167 km from the middle of the area, began a volume at 23:31 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 watch it was issued in

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

IssuedProductOfficeLasted
May 11, 1:12 PM MDTSevere Thunderstorm WatchSPC7 hr

The nearest sounding before it

Salt Lake City I, UT (KSLC), launched 12:00Z, 11.5 hours before the alert went out and 457 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, Salt Lake City I, UT at 12:00Z on 2025-05-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 17 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, Salt Lake City I, UT at 12:00Z on 2025-05-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 192 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
17 J/kg
Mixed-layer CIN
-206 J/kg
Mixed-layer LCL
3436 m above ground
0-6 km bulk shear
31 kt
0-1 km storm-relative helicity
192 m²/s²
0-3 km storm-relative helicity
230 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 Riverton, WY wrote its last area forecast discussion before this severe thunderstorm warning went out at May 11, 4:53 PM MDT, 36 minutes earlier.

Area forecast discussion, May 11, 4:53 PM MDT, 36 minutes before
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Hazardous weather outlook, May 11, 12:57 AM MDT, 16 hours 32 minutes before
Hazardous Weather Outlook
National Weather Service Riverton WY
1257 AM MDT Sun May 11 2025

WYZ001>020-022>030-121100-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn Basin-
Owl Creek and Bridger Mountains-Bighorn Mountains West-
Bighorn Mountains Southeast-Northeast Johnson County-
Southeast Johnson County-Teton and Gros Ventre Mountains-
Jackson Hole-Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
1257 AM MDT Sun May 11 2025

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight.

Scattered rain showers and thunderstorms develop this afternoon.
There is a slight risk of severe thunderstorms across northwest
Wyoming, including YNP. The main threat will be damaging wind gusts,
but hail up to an inch in diameter is also possible (5%). Most of the
area has a chance (30-50%) for strong wind gusts with any showers and
storms that develop this afternoon.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday...Fire weather conditions will be elevated and conditions
would be worse if greenup were not occurring. RH will drop into the
low teens across most of the area Monday afternoon and wind will
increase to 20-30 mph, with gusts of 30-40 mph.

Tuesday through Thursday...A multi-day Spring storm system will
impact western and central Wyoming. Substantial mountain snow will
fall at elevations above 8000 ft, mainly across the Absarokas and
Bighorns. Rainfall will be impactful as well for elevations below
8000 ft. Minor flooding is possible (20-30%) from the Absaroka
Mountains through the Bighorn Basin, over the Bighorn Mountains, and
into northern Johnson County. The best chance for minor flooding
would be Cody west toward Wapiti.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

In the hours before

Special weather statement, May 11, 4:56 PM MDT, 33 minutes before
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Special weather statement, May 11, 4:57 PM MDT, 32 minutes before
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Local storm report, May 11, 5:02 PM MDT, 27 minutes before
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Special weather statement, May 11, 5:15 PM MDT, 14 minutes before
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Special weather statement, May 11, 5:20 PM MDT, 9 minutes before
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Special weather statement, May 11, 5:23 PM MDT, 6 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
May 11, 1:34 PM MDTSevere Thunderstorm WarningRIWFremont26 min
May 11, 2:21 PM MDTSpecial Weather StatementRIWFremont24 min
May 11, 2:45 PM MDTSpecial Weather StatementRIWHot Springs30 min
May 11, 2:49 PM MDTSpecial Weather StatementRIWLincoln41 min
May 11, 2:57 PM MDTSpecial Weather StatementRIW33 min
May 11, 3:12 PM MDTSevere Thunderstorm WarningRIWTeton33 min
May 11, 3:30 PM MDTSpecial Weather StatementRIWLincoln30 min
May 11, 3:44 PM MDTSevere Thunderstorm Warning Considerable damage threatRIWTeton31 min
May 11, 4:01 PM MDTSpecial Weather StatementRIWBig Horn29 min
May 11, 4:13 PM MDTSpecial Weather StatementRIWTeton47 min
May 11, 4:18 PM MDTSpecial Weather StatementRIW42 min
May 11, 4:27 PM MDTSpecial Weather StatementRIWBig Horn33 min
May 11, 4:56 PM MDTSpecial Weather StatementRIWPark34 min
May 11, 4:57 PM MDTSpecial Weather StatementRIW48 min
May 11, 5:15 PM MDTSpecial Weather StatementRIWJohnson30 min
May 11, 5:20 PM MDTSpecial Weather StatementRIWFremont40 min
May 11, 5:23 PM MDTSpecial Weather StatementRIWPark22 min
May 11, 5:50 PM MDTSevere Thunderstorm WarningRIWBig Horn, Park25 min
May 11, 5:58 PM MDTSpecial Weather StatementRIWFremont47 min
May 11, 5:59 PM MDTSpecial Weather StatementRIWBig Horn16 min

Nearby

Severe Thunderstorm Warnings in Wyoming, 2025Every severe thunderstorm warning in 2025

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.