Record rain-on-snow flooding in North Dakota

The Des Lacs River basin (2400 sq km), located in northwest North Dakota, experienced record rain-on-snow flooding on April 19, 1979. Preceeding the flood event, the area experienced: (1) 150 percent of normal precipitation during September, (2) 150 mm of snow accumulation by the end of November, (3) peak snow water equivalent ranging from 50 to 130 mm, (4) 25 mm of new snow water equivalent during the first half of April, (5) air temperatures in excess of 15 degrees C with 60 mm of snow water equivalent on the ground on April 18, and (6) 15 mm of rain on the morning of April 19. A record stage of 6.47 mm was reached at approximately 8 am with a flow of 120.63 sq m/s. The record stage was 0.16 mm above the precious April 1970 record stage and 1.59 mm above flood stage. The return period is estimated to be one in 50 years.