June 2010 Northern Plains tornado outbreak

Tracks of the 74 tornadoes that touched down across the Northern Plains on June 17
Type	Tornado outbreak
Duration	June 16 – 18, 2010
Tornadoes confirmed	93 confirmed
Max. rating1	EF4 tornado
Duration of tornado outbreak2	56 hours, 52 minutes
Fatalities	3 fatalities (+ 2 non-tornadic), 43 injuries
Damage	$117.7 million
Part of the tornado outbreaks of 2010 1Most severe tornado damage; see Enhanced Fujita scale 2Time from first tornado to last tornado

The June 2010 Northern Plains tornado outbreak was one of the most prolific summer tornado outbreaks in the Northern Great Plains of the United States on record. The outbreak began on June 16, with several tornadoes in South Dakota and Montana. The most intense storms took place the following day across much of eastern North Dakota and much of Minnesota. The system produced 93 tornadoes reported across four states while killing three people in Minnesota. Four of the tornadoes were rated as EF4 on the Enhanced Fujita scale, the most violent tornadoes in a 24-hour period since there were five within 15 hours in the 2008 Super Tuesday tornado outbreak. This was the region's first major tornado outbreak of the year and one of the largest on record in the region, comparable to a similar outbreak in June 1992. The 48 tornadoes that touched down in Minnesota on June 17 marked the most active single day in the state's history.^[1] June 17 was the second largest tornado day on record in the meteorological summer, behind the most prolific day of the 2003 South Dakota tornado outbreak on June 24, 2003.

Synopsis

On June 16, 2010, an upper-level area of low pressure and associated trough moved southeastward across the Rocky Mountains into the Great Plains. Along the base of the trough, the presence of a strong mid-level jet stream provided significant instability; however, warm-air aloft was expected to limit the extent of convective development. Moderate to strong deep layer wind shear along with steep lapse rates would allow for the development of supercell thunderstorms with large hail (greater than 2 in (5.1 cm) in diameter). In light of this, the Storm Prediction Center issued a slight-risk of severe weather for portions of Colorado, Montana, Nebraska, North Dakota, South Dakota and Wyoming.^[2]

The Storm Prediction Center issued a moderate risk of severe weather for June 17, 2010, citing a 10% threat for tornadoes, 45% threat for large hail and 45% threat for damaging wind, initially thinking tornadoes would quickly reform into a straight-line wind event. The moderate risk area extended from around Fargo, North Dakota, to Des Moines, Iowa, and Omaha, Nebraska, including the Twin Cities area, with a slight risk area extending across the Upper Midwest. Surface dew points reached the low 70s °F (low 20s °C) with surface temperatures well into 80s °F (near 30 °C) across Minnesota. Surface-based CAPE values were forecast to reach 2000–3000 J/kg.^[3]

The first tornadoes were reported across eastern North Dakota during the mid-afternoon hours where a tornado watch was issued for most of the state as well as extreme northwestern Minnesota closer to the Manitoba and northwestern Ontario borders where many tornadoes, some strong to violent, touched down late that afternoon.^[4] After several tornadoes affected areas near the Grand Forks area and closer to the Canada–US border, the activity eventually shifted into northwestern Minnesota by the late afternoon hours while storms over northern Iowa moved across southern Minnesota near the Interstate 90 corridor producing many tornadoes. Other storms developed over central Minnesota near Interstate 94 but most activity missed the Twin Cities area. The supercells eventually reached the Wisconsin border later that evening and reformed into a squall line, rapidly ending the severe weather outbreak. Isolated tornado reports also occurred across Wisconsin and Iowa. Three people were killed according to KARE-TV including one in Mentor (Polk County), one in Almora (Otter Tail County)^[5] and one near Albert Lea (Freeborn County) an area that sustained heavy damage from a possible long-track tornado.^[6] Large tornadoes were sighted in Kiester in Faribault County and near Ellendale and Blooming Prairie in Steele County, Minnesota.^[7]

The town of Wadena was also hard hit; the high school was heavily damaged by a tornado that prompted a tornado emergency. Extensive damage was also reported in various other communities in Minnesota as well as in North Dakota from either tornadoes or widespread damaging winds such as in the Rochester, Minnesota, area where several buildings, including homes, were heavily damaged on the northern side of the town. A local emergency was declared in Rochester by the mayor following the storms.^[7] The three tornado fatalities in Minnesota were the most for a single outbreak since 1978, and the three EF4 tornadoes were the most on a single day since 1967.^[8]

A moderate risk of severe weather was issued for parts of southern Iowa, northern Missouri and northwestern Illinois during the mid-morning of June 18 citing mostly the threat for damaging winds (45%), though a few tornadoes would be possible as CAPE values of 4000 j/kg were forecast across the Missouri and mid-Mississippi Valleys, especially behind the main derecho.^[9] Such did not materialize, however.

Confirmed tornadoes

June 16 event

June 17 event