A cold front extending from a surface low over Saskatchewan, combined with a strong low pressure trough over northeast Montana amid a very unstable atmosphere to produce numerous thunderstorms, some of which became severe. Later in the evening, some of these storms merged together, produced strong winds as they departed Montana. In addition, heavy rain, caused a few roads to wash out.

Hail in GARFIELD, MONTANA
From 26-MAY-18 17:51:00 to 26-MAY-18 17:51:00 (MST-7)
Location: HAXBY POINT
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Tennis ball size hail was reported via social media. The report included photographic evidence.

Hail in MCCONE, MONTANA
From 26-MAY-18 18:09:00 to 26-MAY-18 18:09:00 (MST-7)
Location: WELDON
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail up to two inches in diameter was reported via social media. The report included photographic evidence.

Hail in MCCONE, MONTANA
From 26-MAY-18 18:10:00 to 26-MAY-18 18:10:00 (MST-7)
Location: WELDON
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A report of golf ball size hail was received via social media. The report included photographic evidence.

Hail in MCCONE, MONTANA
From 26-MAY-18 18:13:00 to 26-MAY-18 18:13:00 (MST-7)
Location: WELDON
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

A report of tennis ball size hail was received via social media. Most of the hail that fell was hen egg size (two inches in diameter), with a few hailstones the size of tennis balls. The report included photographic evidence.

Hail in MCCONE, MONTANA
From 26-MAY-18 19:12:00 to 26-MAY-18 19:12:00 (MST-7)
Location: FT PECK LAKE HANDAR
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported a lot of nickel size hail with a few hail stones the size of quarters.

Hail in DAWSON, MONTANA
From 26-MAY-18 20:30:00 to 26-MAY-18 20:30:00 (MST-7)
Location: RICHEY
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Via social media, public reported golf ball size hail.

Hail in MCCONE, MONTANA
From 26-MAY-18 20:35:00 to 26-MAY-18 20:35:00 (MST-7)
Location: CIRCLE MCCONE CO ARP
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported ping pong ball size hail and heavy rain.

Hail in DAWSON, MONTANA
From 26-MAY-18 20:40:00 to 26-MAY-18 20:40:00 (MST-7)
Location: RICHEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported hail up to the size of quarters and heavy rain.

Hail in DAWSON, MONTANA
From 26-MAY-18 21:30:00 to 26-MAY-18 21:30:00 (MST-7)
Location: LINDSAY DIVIDE DOT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported hail up to the size of quarters and heavy rain.

Thunderstorm Wind in RICHLAND, MONTANA
From 26-MAY-18 21:56:00 to 26-MAY-18 21:56:00 (MST-7)
Location: SIDNEY
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

ASOS site at the Sidney airport measured a 66 mph wind gust.

Hail in MCCONE, MONTANA
From 26-MAY-18 20:06:00 to 26-MAY-18 20:06:00 (MST-7)
Location: CIRCLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported hail at least the size of quarters.

Hail in DAWSON, MONTANA
From 26-MAY-18 21:05:00 to 26-MAY-18 21:05:00 (MST-7)
Location: RICHEY
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported ping pong ball size hail and heavy rain.

Hail in DAWSON, MONTANA
From 26-MAY-18 22:05:00 to 26-MAY-18 22:05:00 (MST-7)
Location: BLOOMFIELD
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported hail up to the size of ping pong balls and heavy rain.

Flash Flood in MCCONE, MONTANA
From 26-MAY-18 22:30:00 to 26-MAY-18 22:30:00 (MST-7)
Location: FT PECK LAKE HANDAR
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported roads washed out leading into Rock Creek State Park.

Hail in MCCONE, MONTANA
From 26-MAY-18 20:25:00 to 26-MAY-18 20:25:00 (MST-7)
Location: CIRCLE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported ping pong ball size hail.

Thunderstorm Wind in DAWSON, MONTANA
From 26-MAY-18 20:37:00 to 26-MAY-18 20:37:00 (MST-7)
Location: BLOOMFIELD
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported two large doors on a 150-foot quonset blown in and part of the fabric roof torn off. Time estimate from radar imagery.

Thunderstorm Wind in RICHLAND, MONTANA
From 26-MAY-18 21:48:00 to 26-MAY-18 21:48:00 (MST-7)
Location: SIOUX PASS DOT
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Sioux Pass MT-16 DOT site measured a 64 mph wind gust.

Flash Flood in DAWSON, MONTANA
From 26-MAY-18 23:00:00 to 26-MAY-18 23:00:00 (MST-7)
Location: LINDSAY DIVIDE DOT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported water around 2 to 3 feet deep flowing over multiple roads.

Thunderstorm Wind in RICHLAND, MONTANA
From 26-MAY-18 22:05:00 to 26-MAY-18 22:05:00 (MST-7)
Location: FAIRVIEW
Magnitude: 60.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Via social media, public reported tree limbs broken and damage to a field.

Hail in MCCONE, MONTANA
From 26-MAY-18 19:36:00 to 26-MAY-18 19:36:00 (MST-7)
Location: BROCKWAY
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS employee reported hail up to the size of ping pong balls.