A powerful storm system dumped up to 2 feet of snow in the Rockies, unleashed heavy thundershowers in the nation’s midsection and lashed both with gale-force winds. Thunderstorms in Minnesota raked the Twin Cities suburbs with hail as big as tennis balls and spawned tornadoes in the northwestern portion of the state. No injuries were reported. Up to 20 inches of snow was reported in the Big Horn Mountains of Wyoming. Strong winds were common from the Rockies to the upper Mississippi Valley. A 92-m.p.h. gust hit Rollinsville, Colo., and a 110-m.p.h. gust was felt near Boulder, Colo.