Right now
The most recent data we hold from NOAA arrived 21 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
This alert expired on 18 May 2026 at 04:00 UTC. It is kept here as a record.
What the source measured
NOAA reported: Tornado Watch issued May 17 at 9:17PM CDT until May 17 at 11:00PM CDT by NWS Omaha/Valley NE
Urban PEI: 181,553 within a heuristic 50 km radius; not unique people.
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 55 out of 100.
This is our versioned heuristic index, not source severity or a calibrated probability. Urban PEI does not count unique people.
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 | High |
| Calamity Score (ours) | 55 / 100 |
| Legacy data-support index | 0.80/1 |
| Coordinates | 42.0000, -93.2000 |
| Nearest City | Marshalltown (25 km) |
| Urban exposure index (PEI) | 181.6K within 50 km |
| Impact Tier | severe |
| Timestamp | 2026-05-18T02:17:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Tornado Watch_noaa_urn:oid:2.49.0.1.840.0.020f07cbb10712406e2c22211325232d |
Physical priority index · v1. Heuristic priority, not calibrated probability, predictive accuracy or damage. The legacy data-support index combines assigned source support and field availability. Urban PEI is distance-weighted and does not count unique people; zero does not establish that nobody is present. Model cards.
Source and revision timeline
Source: noaa. Occurrence: 2026-05-18T02:17:00.000Z.
First archived: 2026-05-18T03:10:40.791Z. Material modification: not recorded.
Retained revisions are prospective; earlier versions may be unavailable. No revision entry does not prove that a record never changed.
Score Breakdown
Technical Details
| Event | Tornado Watch |
| Urgency | Future |
| Certainty | Possible |
| AreaDesc | Fremont, IA; Harrison, IA; Mills, IA; Montgomery, IA; Page, IA; Pottawattamie, IA; Shelby, IA; Cass, NE; Douglas, NE; Gage, NE; Jefferson, NE; Johnson, NE; Lancaster, NE; Nemaha, NE; Otoe, NE; Pawnee, NE; Richardson, NE; Sarpy, NE; Washington, NE; Bremer, IA; Butler, IA; Cerro Gordo, IA; Emmet, IA; Franklin, IA; Hancock, IA; Humboldt, IA; Kossuth, IA; Palo Alto, IA; Pocahontas, IA; Winnebago, IA; Worth, IA; Wright, IA; Adair, IA; Adams, IA; Audubon, IA; Black Hawk, IA; Boone, IA; Calhoun, IA; Carroll, IA; Cass, IA; Clarke, IA; Crawford, IA; Dallas, IA; Decatur, IA; Greene, IA; Grundy, IA; Guthrie, IA; Hamilton, IA; Hardin, IA; Jasper, IA; Lucas, IA; Madison, IA; Mahaska, IA; Marion, IA; Marshall, IA; Monroe, IA; Polk, IA; Poweshiek, IA; Ringgold, IA; Sac, IA; Story, IA; Tama, IA; Taylor, IA; Union, IA; Warren, IA; Wayne, IA; Webster, IA and 2 more areas |
| Headline | Tornado Watch issued May 17 at 9:17PM CDT until May 17 at 11:00PM CDT by NWS Omaha/Valley NE |
| Expires | 2026-05-17T23:00:00-05:00 |
| SenderName | NWS Omaha/Valley NE |
| HasExactCoords | false |
| MergedCount | 5 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.020f07cbb10712406e2c22211325232d70dcb45d.003.1","noaa_urn:oid:2.49.0.1.840.0.4f5dbab088346cca8989a5941a3bf5bef6cae3a9.002.1","noaa_urn:oid:2.49.0.1.840.0.4f5dbab088346cca8989a5941a3bf5bef6cae3a9.001.1","noaa_urn:oid:2.49.0.1.840.0.f58d793523b6d3e8507eadbac09c00f8546324ea.002.1","noaa_urn:oid:2.49.0.1.840.0.f58d793523b6d3e8507eadbac09c00f8546324ea.001.1"] |
Safety Information
If a tornado warning is issued: go to a basement or an interior room on the lowest floor, away from windows. A vehicle and a mobile home are not shelter. Cover your head and neck. Wait for the official all-clear before going outside, and watch for downed power lines and gas leaks afterwards.
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.
Review the area, threshold and delivery channel in your account.
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