A deep upper trough extending from the Pacific Northwest to the Great Basin provided a deep southerly flow aloft over the area. This allowed thunderstorms over western Garfield, southern Phillips and southwest Valley counties to contain a great deal of moisture.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GGW wrote it up.
A deep upper trough extending from the Pacific Northwest to the Great Basin provided a deep southerly flow aloft over the area. This allowed thunderstorms over western Garfield, southern Phillips and southwest Valley counties to contain a great deal of moisture. Heavy rain and hail accompanied these storms as they mainly tracked northwest and occurred in remote locations.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
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</html>The Glasgow radar (KGGW), 72 km away, was scanning. The volume nearest the first event began at 00:10 UTC.
3 hail, 1 heavy rain. Local standard time, as filed.
Local residents reported up to ping pong size hail with the storm. The last report at 530 MST reported nickel to quarter size hail.
Spotters reported that the storm intensified as it moved east with hail initially reported at nickle-size and the second reporting 1.5 inch diameter.
Heavy rain estimated at several inches (radar estimated at five inches) fell mainly in the Second and Third Creek basins in the southern portion of the county resulting in runoff over a roadway (Dry Fork Road). This runoff began during the evening of the 18th and continued into the morning of the 19th. This is only the second time that this has happened in the past twelve years (according to the Trained Spotter). The damaged section of road is about mile east of the Dry Fork Bridge. The force of the runoff carried away a portion of the south shoulder of the road; creating an abrupt drop off about 75 feet long and 3 feet deep.
Nickel size hail along with heavy rain and wind gusts to 30 mph was initially reported at eight miles north of Fourchette, then half-dollar size hail was reported for 30 minutes 23 miles east-southeast of Zortman.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2010Every state in 2010This day in weather historyWarnings in Montana, May 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 224470, 224476, 224496, 224486.