An upper low to the west of the area coupled with a low level jet that brought an unstable airmass from the central plains to produce severe thunderstorms and an isolated tornado.

Hail in MCCONE, MONTANA
From 27-MAY-10 19:52:00 to 27-MAY-10 19:52:00 (MST-7)
Location: BROCKWAY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A resident reported hail about the size of quarters.

Hail in MCCONE, MONTANA
From 27-MAY-10 20:40:00 to 27-MAY-10 20:40:00 (MST-7)
Location: WELDON
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter 3 miles west of Weldon reported 1.75 inch hail; a member of the public reported 1.0 inch hail 3 miles southwest of Weldon.

Hail in DAWSON, MONTANA
From 27-MAY-10 21:10:00 to 27-MAY-10 21:14:00 (MST-7)
Location: LINDSAY DIVIDE DOT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public reported 1.75 inches 12 miles northwest of Lindsay at 2114 MST. Smaller hail of 1.0 inch stones was reported 15 miles east of Circle at 2110 MST.

Hail in GARFIELD, MONTANA
From 27-MAY-10 21:20:00 to 27-MAY-10 21:40:00 (MST-7)
Location: JORDAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Quarter sized hail piled up to a foot on Highway 59.

Heavy Rain in DAWSON, MONTANA
From 26-MAY-10 20:00:00 to 27-MAY-10 06:00:00 (MST-7)
Location: GLENDIVE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRahs observer reported 1.12 inches of rainfall overnight. This brought the monthly total so far for him to 5.42 inches.

Hail in ROOSEVELT, MONTANA
From 28-MAY-10 00:00:00 to 28-MAY-10 00:00:00 (MST-7)
Location: WOLF PT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Resident reported one inch hail.

Hail in MCCONE, MONTANA
From 27-MAY-10 20:53:00 to 27-MAY-10 20:53:00 (MST-7)
Location: CIRCLE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported penny size hail.

Hail in GARFIELD, MONTANA
From 27-MAY-10 21:20:00 to 27-MAY-10 21:20:00 (MST-7)
Location: JORDAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported quarter size hail.

Flash Flood in VALLEY, MONTANA
From 27-MAY-10 21:00:00 to 28-MAY-10 02:00:00 (MST-7)
Location: DUCK CREEK
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

Official reported areas of Kiwanis Park (Downstream Recreation Area) were under water. Water was also reported to be over Highway 24 near the Duck Creek Road.

Hail in GARFIELD, MONTANA
From 27-MAY-10 22:02:00 to 27-MAY-10 22:02:00 (MST-7)
Location: VAN NORMAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Trained Spotter and Coop Observer reported quarter-size hail.

Hail in MCCONE, MONTANA
From 27-MAY-10 19:55:00 to 27-MAY-10 20:53:00 (MST-7)
Location: BROCKWAY
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

At 2000 MST eleven miles south-southwest of Brockway tennis ball size hail (2.5 inch diameter) was reported for 5 minutes. Smaller reports of hail included: 0.75 inch stones at 2010 MST 14 miles west of Circle; 0.75 inch stones at 2035 MST 10 miles south of Circle; and 0.75 inch stones at 2053 MST 7 miles ESE Circle.

Tornado in MCCONE, MONTANA
From 27-MAY-10 19:49:00 to 27-MAY-10 19:49:00 (MST-7)
Location: BROCKWAY
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Two sets of storm chasers reported a rope tornado that touched down sometime between 854 and 859 pm MDT. There were some conflicts between reports on timing and exact location. One report had the tornado on the ground for 15 seconds.

Flash Flood in GARFIELD, MONTANA
From 27-MAY-10 21:00:00 to 28-MAY-10 02:00:00 (MST-7)
Location: VAN NORMAN
Flood cause: Dam / Levee Break
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain during the evening brought the failure of a local dam. The dam's name was 7-Tree and the gash or hole made was 50-60 feet wide by 40-50 feet deep.

Flash Flood in MCCONE, MONTANA
From 27-MAY-10 21:00:00 to 28-MAY-10 02:00:00 (MST-7)
Location: FT PECK LAKE HANDAR
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

Spotter reported water over Highway 24 at North Rock Creek turnoff. Adjacent fields were covered with two to three feet of water.