Alert archive / Wyoming / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 63, NWS Riverton, WY

September 19, 2026Natrona County, Wyoming

NWS Riverton, WY issued this severe thunderstorm warning at Sep 19, 2026, 6:59 PM MDT for Natrona 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
Sep 19, 2026, 6:59 PM MDT (00:59 UTC)
Expired
Sep 19, 2026, 7:30 PM MDT
In force
31 min
Issued by
NWS Riverton, WY
Area
Storm-based polygon
Tornado
Possible
Hail
1.0 in
Wind
60.0 mph

County Natrona County, WY

The radar

The Riverton/Lander radar (KRIW), 137 km from the middle of the area, began a volume at 00:59 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

Grand Junction, CO (KGJT), launched 00:00Z, 1.0 hours before the alert went out and 449 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, Grand Junction, CO at 00:00Z on 2026-09-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 599 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, Grand Junction, CO at 00:00Z on 2026-09-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 82 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
599 J/kg
Mixed-layer CIN
-63 J/kg
Mixed-layer LCL
1884 m above ground
0-6 km bulk shear
41 kt
0-1 km storm-relative helicity
82 m²/s²
0-3 km storm-relative helicity
140 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.8

Open this sounding in Storm Lab

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 19, 6:14 PM MDTAreal Flood AdvisoryRIWFremont3 hr
Sep 19, 6:22 PM MDTSpecial Weather StatementRIWNatrona38 min
Sep 19, 6:25 PM MDTFlash Flood WarningRIWFremont3 hr
Sep 19, 6:37 PM MDTSevere Thunderstorm WarningRIWNatrona23 min
Sep 19, 7:08 PM MDTSpecial Weather StatementRIWNatrona37 min
Sep 19, 7:39 PM MDTAreal Flood AdvisoryRIWFremont3 hr

Nearby

Severe Thunderstorm Warnings in Wyoming, 2026Every severe thunderstorm warning in 2026

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.