User:CapeVerdeWave/Tornado outbreak sequence of May 4–10, 1965

A widespread and destructive tornado outbreak sequence impacted the Midwestern United States between May 4–10, 1965.

Background and impact
On the morning of May 6, 1965, a series of low-pressure areas, consisting of dual cyclones, was present over and east of the Great Basin, roughly straddling the Continental Divide. Meanwhile, a warm front extended eastward over Minneapolis–St. Paul, attended by temperatures in the high 70s °F. An ongoing mesoscale convective system deposited outflow boundaries in the area, which locally contributed to enhanced wind shear. As a result, numerous supercells developed and trained over the Twin Cities, producing intense tornadoes. These tornadoes were the most severe on record in the Twin Cities metropolitan area. Roughly two days later, a vigorous trough generated severe thunderstorms over the Front Range, immediately preceding a significant tornado episode over the High Plains on May 8. Potent atmospheric instability contributed to the outbreak of storms on the latter date.

Confirmed tornadoes
Prior to 1990, there is a likely undercount of tornadoes, particularly E/F0–1, with reports of weaker tornadoes becoming more common as population increased. A sharp increase in the annual average E/F0–1 count by approximately 200 tornadoes was noted upon the implementation of NEXRAD Doppler weather radar in 1990–1991. 1974 marked the first year where significant tornado (E/F2+) counts became homogenous with contemporary values, attributed to the consistent implementation of Fujita scale assessments. Numerous discrepancies on the details of tornadoes in this outbreak exist between sources. The total count of tornadoes and ratings differs from various agencies accordingly. The list below documents information from the most contemporary official sources alongside assessments from tornado historian Thomas P. Grazulis.

Cologne–Island Park–Navarre–Orono, Minnesota
This was the first of four violent, destructive tornadoes to impact Minneapolis–St. Paul on May 6. According to Grazulis, it was also the same as the Hamburg–Norwood Young America F2, traveled 40 mi, and may have begun at 00:50 UTC. It first destroyed three barns near Cologne, causing F2 damage in the area; this segment of the path may have actually been a separate tornado and occurred at 01:15 UTC. The tornado quickly intensified and widened near Waconia, reaching a peak width of 1/2 to 3/4 mi. Trees were snapped and downed in this area. The tornado then may have lifted and dissipated before reforming west of Lake Minnetonka, along Highway 7. Entering the Mound area, the tornado destroyed three outbuildings and 17 homes at Island Park, causing all known fatalities there. The deaths occurred singly, each in a separate home. Subsequently, the tornado struck Spring Park and largely destroyed the Navarre community. In the Spring Park–Navarre area a resort, a number of boats, and about 30 homes were destroyed, 16 of which were at Navarre alone. West of Wayzata the tornado destroyed a barn shortly before dissipating. According to the publication Storm Data the path may have extended as far as Hamel.

Chanhassen–Lotus Lake–Christmas Lake–Deephaven, Minnesota
The second of the four violent tornadoes to impact the Twin Cities on May 6 may have actually begun 23 minutes earlier than its predecessor. It produced its first damage near Chanhassen, impacting a farmstead. Near Chanhassen the tornado destroyed or damaged 30 homes. A pair of clocks near Chanhassen recorded the time of touchdown as 00:27 UTC. Heading northward, the tornado damaged a lumberyard and a shopping center. Nearing Lotus Lake, the tornado destroyed or damaged 35 homes. 50 additional homes were destroyed or damaged near Christmas Lake. The tornado subsequently attained its maximum intensity in Deephaven. There it destroyed or damaged 100 homes, a number of which were reportedly leveled; of these, some were described as having been "large and expensive." After passing through Deephaven, the tornado apparently dissipated. However, sporadic reports of damage suggested that the parent storm continued to generate possible tornadoes. One of these tornadoes reportedly damaged six homes along Highway 100 in Golden Valley, becoming the first of two tornadoes to impact this area on the same day. Another of these tornadoes became known as the third Fridley tornado, causing minor damage at 01:10 UTC. However, neither of these two tornadoes is officially listed, though they were mentioned in the publication Storm Data. Until 1973 U.S. Weather Bureau/National Weather Service (NWS) records listed these tornadoes as well.

Fridley–Spring Lake Park–Blaine, Minnesota
This was the first—possibly the second—of three major tornadoes to impact Fridley on May 6. One industrial plant in Fridley, known as Northern Ordinance, may have been hit by all three tornadoes, the third of which is not officially listed; as a result, the factory incurred more than $2 million in losses and was incapacitated for more than a month. The first Fridley tornado began at Northern Ordinance and was widely visible. It soon impacted the primary school-and-park complex in Fridley, along with the Fridley Trailer Court and several hundred homes. Both this and the second Fridley tornado impacted the trailer court, destroying a total of 200 trailers. A female infant was killed at the trailer court while being bathed. At Fridley Junior High School, an evening program was in progress with more than 300 people in attendance when the tornado struck, but only a single injury occurred there. After striking the school and the trailer court, the tornado intensified significantly and attained its peak intensity, striking Spring Lake Park. There the tornado destroyed 150 homes, some of which sustained F4-level damage. Additionally, three-fourths of the businesses in Spring Lake Park were destroyed, and 900 people lost their homes. Contemporaneous reports suggested that the tornado apparently weakened rapidly and dissipated before exiting the town limits, though official records indicate that the tornado ended in southwestern Blaine. Farther on, scattered wind-related damage was reported in connection with the parent storm, at Braham.

Golden Valley–Fridley–Mounds View–Centerville, Minnesota
The last of the four violent tornadoes to hit the Twin Cities on May 6 touched down in Golden Valley, damaging eight businesses and 25 homes in town. The time of its formation is somewhat uncertain and may have been 02:40 UTC. Leaving Golden Valley, the tornado apparently lifted. Damage resumed in Fridley, including the Fridley Trailer Court. In Fridley this, the preceding, and the unofficial "third" Fridley tornado hit several of the same properties. The second of the two confirmed tornadoes to hit Fridley passed between the paths of the first and unofficial "third" tornadoes in town. Exiting Fridley, the tornado rapidly intensified. It then struck Mounds View, where damages reached $1 million. All known fatalities and all but eight injuries in association with the tornado occurred there. In all, the tornado destroyed 46 homes in Mounds View, many of which sustained F4-level damage. Six apartments in town were destroyed as well. Once past Mounds View, the tornado produced discontinuous, "skipping" damage. It crossed a number of lakes, including Centerville Lake, and damaged four farmsteads before dissipating. The parent storm continued on and may have produced a separate tornado near Almelund. This possible tornado damaged outbuildings on three farmsteads and splintered trees. However, it was never officially documented and listed as a tornado.

Possible tornadoes
A possible tornado damaged a pair of farmsteads southwest of New York Mills in Becker County, Minnesota, causing $3,000 in losses.