Severe Weather near Greater Upper Marlboro
Right now
The most recent data we hold from NOAA arrived 49 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 20 May 2026 at 22:00 UTC. It is kept here as a record.
It is the 616th strongest of the 787 detections recorded within 20 km of this point since 10 March 2026. Another comparable one was recorded here earlier the same day. 13 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Special Marine Warning issued May 20 at 4:29PM EDT until May 20 at 6:00PM EDT by NWS Baltimore MD/Washington DC
An estimated 4,347,846 people live within 50 km of this point.
Nearby, since 10 March 2026
- July 9, 2026 · score 52 · 2.1 km
- August 6, 2026 · score 66 · 6.6 km
- March 17, 2026 · score 52 · 6.8 km
How we know
Confirmed by 4 independent sources, including NOAA.
Our own score for this event is 52 out of 100, at 89 % 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) | 52 / 100 |
| Our confidence | 89% |
| Coordinates | 38.8303, -76.7926 |
| Nearest City | Greater Upper Marlboro (4 km) |
| Population Exposed | 4.3M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-05-20T20:29:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Special Marine Warning_noaa_urn:oid:2.49.0.1.840.0.209b5edb71adaf3be454108e311b5437 |
Score Breakdown
Technical Details
| Event | Special Marine Warning |
| Urgency | Immediate |
| Certainty | Likely |
| AreaDesc | Tidal Potomac from Indian Head to Cobb Island MD; Chesapeake Bay north of Pooles Island MD; Chesapeake Bay from Pooles Island to Sandy Point MD; Patapsco River including Baltimore Harbor; Chester River to Queenstown MD; Tidal Potomac from Key Bridge to Indian Head MD |
| Headline | Special Marine Warning issued May 20 at 4:29PM EDT until May 20 at 6:00PM EDT by NWS Baltimore MD/Washington DC |
| Expires | 2026-05-20T18:00:00-04:00 |
| SenderName | NWS Baltimore MD/Washington DC |
| HasExactCoords | true |
| MergedCount | 3 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.209b5edb71adaf3be454108e311b5437d322584f.001.1","noaa_urn:oid:2.49.0.1.840.0.cec047dfb21a1632e26f971efc9364cd5a7a3833.001.1","noaa_urn:oid:2.49.0.1.840.0.2f7686d74deadee59eea24a383cb140a5a7e2d31.001.1"] |
| Google News RssFeed | weather |
| Google News SourceName | Rolling Out |
| MergedSources | [{"id":"gnews_weather_494249_169","source":"google_news","severity":"medium","severityValue":40,"timestamp":1779296414000,"latitude":39.29,"longitude":-76.61},{"id":"gnews_weather_494251_179","source":"google_news","severity":"medium","severityValue":40,"timestamp":1779305596000,"latitude":38.9,"longitude":-77.04},{"id":"gnews_weather_494250_182","source":"google_news","severity":"medium","severityValue":40,"timestamp":1779300289000,"latitude":39.29,"longitude":-76.61}] |
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.
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