Tornado Watch number 217 was in effect during this event.
Thunderstorms developing in the afternoon, in the warm sector of an area of low pressure, continued into the evening as an upper level short wave trough moved into the Dakotas. While the tornado threat did materialize as predicted, steep mid-level lapse rates, Mean Layer CAPE over 2000 Joules/KG, and deep layer shear to 45 knots supported updraft longevity and resulted in numerous reports of large hail.  As the evening progressed the storms formed into a well-organized quasi-linear storm complex over south central North Dakota, producing damaging winds and torrential rain. The heaviest rain, up to six inches in central Sioux County, led to flash flooding from Selfridge to Porcupine.

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 15:55:00 to 25-MAY-13 16:00:00 (MST-7)
Location: HAYNES
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 16:50:00 to 25-MAY-13 16:55:00 (MST-7)
Location: HAYNES
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:00:00 to 25-MAY-13 14:10:00 (MST-7)
Location: REEDER
Magnitude: 2.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

There was damage to buildings and automobiles.

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:00:00 to 25-MAY-13 14:05:00 (MST-7)
Location: REEDER
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:10:00 to 25-MAY-13 14:15:00 (MST-7)
Location: BUCYRUS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:35:00 to 25-MAY-13 14:41:00 (MST-7)
Location: HETTINGER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 15:06:00 to 25-MAY-13 15:12:00 (MST-7)
Location: BUCYRUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Flash Flood in SIOUX, NORTH DAKOTA
From 25-MAY-13 19:45:00 to 25-MAY-13 23:35:00 (MST-7)
Location: SOLEN
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 50.00K
Reported by: Law Enforcement

Torrential rain, with reports up to six inches, resulted in a flash flood over central Sioux County.  The reports were consistent with Doppler Radar rain estimates. State Highway 6 was closed due to a foot of water flowing rapidly over the road at mile marker 18. Numerous county and tribal roads were flooded and had severe wash outs. Culverts were washed completely out in some cases.

Thunderstorm Wind in STARK, NORTH DAKOTA
From 25-MAY-13 12:35:00 to 25-MAY-13 12:40:00 (MST-7)
Location: (DIK)DICKINSON MUNI
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:10:00 to 25-MAY-13 14:15:00 (MST-7)
Location: REEDER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in ADAMS, NORTH DAKOTA
From 25-MAY-13 14:35:00 to 25-MAY-13 14:45:00 (MST-7)
Location: HETTINGER
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in GRANT, NORTH DAKOTA
From 25-MAY-13 16:00:00 to 25-MAY-13 16:05:00 (MST-7)
Location: HEIL
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in GRANT, NORTH DAKOTA
From 25-MAY-13 16:00:00 to 25-MAY-13 16:05:00 (MST-7)
Location: HEIL
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain accompanied the strong winds.

Heavy Rain in GRANT, NORTH DAKOTA
From 25-MAY-13 16:55:00 to 25-MAY-13 17:35:00 (MST-7)
Location: RALEIGH
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Measured 1.4 inches of rain in 40 minutes.

Hail in STARK, NORTH DAKOTA
From 25-MAY-13 12:49:00 to 25-MAY-13 12:55:00 (MST-7)
Location: (DIK)DICKINSON MUNI
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in BOWMAN, NORTH DAKOTA
From 25-MAY-13 13:30:00 to 25-MAY-13 13:36:00 (MST-7)
Location: SCRANTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Hail in BOWMAN, NORTH DAKOTA
From 25-MAY-13 13:43:00 to 25-MAY-13 13:48:00 (MST-7)
Location: GASCOYNE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter