This alert expired on 21 May 2026 at 23:30 UTC. It is kept here as a record.
It is the 2nd strongest of the 38 detections recorded within 20 km of this point since 9 May 2026. Another comparable one was recorded here earlier the same day. 5 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued May 21 at 4:41PM MDT until May 21 at 5:30PM MDT by NWS Cheyenne WY
Nearby, since 9 May 2026
- May 30, 2026 · score 16 · 2.4 km
- May 9, 2026 · score 22 · 8.3 km
- June 9, 2026 · score 22 · 15.7 km
How we know
Confirmed by 2 independent sources, including NOAA.
Our own score for this event is 22 out of 100, at 63 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Computed under scoring rules v1. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Medium |
| Calamity Score (ours) | 22 / 100 |
| Our confidence | 63% |
| Coordinates | 40.7919, -103.6038 |
| Nearest City | Greeley (102 km) |
| Impact Tier | minor |
| Timestamp | 2026-05-21T22:41:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.346fbaa3fa950730186dad77e4fc887e |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Banner, NE; Kimball, NE; Adams, CO; Eastern Arapahoe, CO; Washington, CO; Logan, CO |
| Headline | Severe Thunderstorm Warning issued May 21 at 4:41PM MDT until May 21 at 5:30PM MDT by NWS Cheyenne WY |
| Expires | 2026-05-21T17:30:00-06:00 |
| SenderName | NWS Cheyenne WY |
| HasExactCoords | true |
| MergedCount | 4 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.346fbaa3fa950730186dad77e4fc887eff1cac8f.001.1","noaa_urn:oid:2.49.0.1.840.0.c1aa4d30bf392380ed8794a1171cce73948cf960.001.1","noaa_urn:oid:2.49.0.1.840.0.8a2138c81a0b888bac57fdf576a9feab507221c5.001.1","noaa_urn:oid:2.49.0.1.840.0.4966e66311c42e3c3aa6622b4ce9bc5625f1e7e9.001.1"] |
| Iem TypeSummary | W |
| Iem City | 3 W Pine Bluffs |
| Iem County | Laramie |
| Iem State | WY |
| Iem Wfo | CYS |
| Iem Remark | Report of a landspout reported by fire department. Boundary collision observed on radar at the time of the call. |
| MergedSources | [{"id":"iem_W_41.180_-104.130_1779401040000","source":"iem","severity":"low","severityValue":25,"timestamp":1779401040000,"latitude":41.18,"longitude":-104.13}] |
Safety Information
Always follow official guidance from your local emergency management agency. This platform provides scientific monitoring data and is not a substitute for official warnings. If you are in immediate danger, contact your local emergency number.
Series begins 8 March 2026. Comparisons refer to that period only. Collection gap: 14-26 August 2026.
This data is aggregated algorithmically from scientific sources. Not a replacement for official emergency warnings.
Want to know when something happens in this area?
Calamity.live data shows a weather event with CalamityScore 22/100 (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 185 scientific monitoring sources.