By early evening of the 22nd, a triple point had formed over north central South Dakota, with a surface boundary extending to its north and south. A warm front extended to the southeast, or down into southwest Minnesota. Near this triple point, temperatures had warmed into the mid to upper 80s with dew points in the mid to upper 60s. The heat and humidity was more limited in eastern North Dakota and the northwest quarter of Minnesota, where cloud cover held temperatures in the upper 60s and lower 70s with dew points in the mid to upper 50s. As the low level jet kicked in during the evening and overnight hours, strong warm and moist advection continued above the surface layer, fueling storms into portions of eastern North Dakota and the northwest quarter of Minnesota. Most of these storms produced large hail, but some stronger wind gusts also occurred.

Hail in GRIGGS, NORTH DAKOTA
From 22-MAY-10 20:18:00 to 22-MAY-10 20:18:00 (CST-6)
Location: KARNAK
Magnitude: 0.88 
Reported by: Trained Spotter

Hail in SARGENT, NORTH DAKOTA
From 22-MAY-10 21:30:00 to 22-MAY-10 21:35:00 (CST-6)
Location: FORMAN
Magnitude: 1.00 
Reported by: Public

The report of dime to quarter size hail came from a North Dakota Atmospheric Resources Board observer.

Hail in GRAND FORKS, NORTH DAKOTA
From 22-MAY-10 21:30:00 to 22-MAY-10 21:40:00 (CST-6)
Location: HOLMES
Magnitude: 0.75 
Reported by: Public

An ARB observer reported the penny sized hail.

Thunderstorm Wind in RICHLAND, NORTH DAKOTA
From 23-MAY-10 00:00:00 to 23-MAY-10 00:00:00 (CST-6)
Location: MOSELLE
Magnitude: 60.00 EG
Reported by: Law Enforcement

The Richland County Sheriff reported a corridor from five miles west to three miles east of Wyndmere, where there were several reports of trees down in yards. There were also numerous reports of one to two inch diameter tree branches blown down across highway 13 in this region.

Hail in STEELE, NORTH DAKOTA
From 22-MAY-10 20:48:00 to 22-MAY-10 20:48:00 (CST-6)
Location: BLABON
Magnitude: 1.25 
Reported by: Public

Hail in SARGENT, NORTH DAKOTA
From 22-MAY-10 21:00:00 to 22-MAY-10 21:00:00 (CST-6)
Location: NICHOLSON
Magnitude: 1.00 
Reported by: Public

Hail in STEELE, NORTH DAKOTA
From 22-MAY-10 21:10:00 to 22-MAY-10 21:10:00 (CST-6)
Location: SHERBROOKE
Magnitude: 1.75 
Reported by: Trained Spotter

Hail in GRAND FORKS, NORTH DAKOTA
From 22-MAY-10 21:30:00 to 22-MAY-10 21:30:00 (CST-6)
Location: HOLMES
Magnitude: 1.00 
Reported by: Public

Hail in SARGENT, NORTH DAKOTA
From 22-MAY-10 22:10:00 to 22-MAY-10 22:10:00 (CST-6)
Location: RANSOM
Magnitude: 1.00 
Reported by: Trained Spotter

Hail in RICHLAND, NORTH DAKOTA
From 22-MAY-10 23:10:00 to 22-MAY-10 23:10:00 (CST-6)
Location: GREAT BEND
Magnitude: 0.88 
Reported by: Law Enforcement

Flash Flood in GRIGGS, NORTH DAKOTA
From 23-MAY-10 02:00:00 to 23-MAY-10 04:00:00 (CST-6)
Location: HANNAFORD
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 50.00K
Reported by: Emergency Manager

Heavy rains of three to five inches produced flooding in fields and across a few low lying roads.

Flash Flood in NELSON, NORTH DAKOTA
From 23-MAY-10 03:00:00 to 23-MAY-10 05:00:00 (CST-6)
Location: MICHIGAN CITY
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 50.00K
Reported by: Newspaper

Heavy rains of three to five inches produced runoff which inundated city sewer lift stations and flooded several basements.

Flash Flood in STEELE, NORTH DAKOTA
From 22-MAY-10 23:55:00 to 23-MAY-10 05:00:00 (CST-6)
Location: SHARON
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 50.00K
Reported by: Law Enforcement

Two to four inches of rain fell over portions of northwest Steele County, causing rapid rises in water levels at some locations. Two feet of water flowed over state highway 32 about six miles south of Finley. About a mile south of the junction of highways 200 and 32, three feet of water covered the road for about 70 feet.