Right now
The most recent data we hold from NOAA arrived 4 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
Nothing else has been detected within 20 km in the last 24 hours.
This alert expired on 28 July 2026 at 21:00 UTC. It is kept here as a record.
It is the 82nd strongest of the 241 detections recorded within 20 km of this point since 16 March 2026. The last comparable one was on 9 July 2026.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued July 28 at 4:27PM EDT until July 28 at 5:00PM EDT by NWS Baltimore MD/Washington DC
Urban PEI: 351,469 within a heuristic 50 km radius; not unique people.
Nearby, since 16 March 2026
- September 3, 2026 · score 37 · 2.9 km
- September 2, 2026 · score 37 · 2.9 km
- July 28, 2026 · score 48 · 5.5 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 43 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 | Medium |
| Calamity Score (ours) | 43 / 100 |
| Legacy data-support index | 0.79/1 |
| Coordinates | 39.4947, -77.5872 |
| Nearest City | Frederick (18 km) |
| Urban exposure index (PEI) | 351.5K within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-07-28T20:27:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.4b6a8b03cac6f4034769dc92a0e8a2b4 |
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: 2026-07-28T20:27:00.000Z.
First archived: 2026-07-28T20:34:30.198Z. 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 | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Frederick, MD; Washington, MD; Jefferson, WV; Clarke, VA; Fauquier, VA; Frederick, VA; Loudoun, VA; Page, VA; Rappahannock, VA; Shenandoah, VA; Warren, VA; Clarke, VA; Loudoun, VA; Jefferson, WV and 3 more areas |
| Headline | Severe Thunderstorm Warning issued July 28 at 4:27PM EDT until July 28 at 5:00PM EDT by NWS Baltimore MD/Washington DC |
| Expires | 2026-07-28T17:00:00-04:00 |
| SenderName | NWS Baltimore MD/Washington DC |
| HasExactCoords | true |
| MergedCount | 7 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.4b6a8b03cac6f4034769dc92a0e8a2b482513ca2.001.1","noaa_urn:oid:2.49.0.1.840.0.b7e3d727f34f36a558035502a7b70aef347d1b85.001.1","noaa_urn:oid:2.49.0.1.840.0.24d195e14ba164c9fcb4182cbcc73289f2e179f2.001.1","noaa_urn:oid:2.49.0.1.840.0.cfab4aad057d31865eb8fdc53daef90c7a24d382.001.1","noaa_urn:oid:2.49.0.1.840.0.7262dacb9e2b01b3b86656a718a90af587f204db.001.1","noaa_urn:oid:2.49.0.1.840.0.999df35901958467fc46b568101d78936479bdc8.001.1","noaa_urn:oid:2.49.0.1.840.0.ab71974b9695edd52913389011e4f7dd7e350241.001.1"] |
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.
Review the area, threshold and delivery channel in your account.
Want to know when something happens near Frederick?