Flood — Yukon Flats Nearby Uplands, Alaska

2023-05-13 to 2023-05-14 · near Circle, Yukon Flats Nearby Uplands, Alaska

Event narrative

Record flooding occurred on the evening of May 13th at Circle. The Riverwatch team flew between Eagle and Circle on the afternoon of May 13th. During the day on May 13th, an observer 28 miles upriver of Circle reported the highest water he'd ever seen. The Riverwatch team observed widespread flooding (trees inundated, islands covered in ice, river well out of bank) upriver from Circle. Ice had degraded during the day in warm conditions and the Riverwatch team saw ice start to move while they were in Circle at 5 pm May 13th. Prior to landing, the Riverwatch team observed a roughly 90-mile-long run of ice behind the breakup front. For context, that is the longest run of ice that this Riverwatch team could remember ever seeing. The Riverwatch team circled above several times after takeoff and observed ice moving, and progressive disintegration of larger ice sheets (indicating weakness and that given the momentum of the river ice jams were unlikely). The flooding came on quickly; the water rose extremely fast and major flooding was first reported at around 8 pm. There was extensive damage, with flood waters estimated to be higher than the previous flood of record, 1945. The store had water up to the ceiling of the first floor. Ice moved into town and damaged homes with stranded ice throughout the community. Most structures in the town flooded and also flooded the airport apron and taxiway. The Riverwatch team flew over the next day and did not observe evidence of ice jamming but believe that the river simply slowed at the S-curves (where the Yukon becomes more braided) and compounded with historically high water levels. By the next morning, floodwaters had receded and had dropped below the airport access road by 3 pm May 14th.

Wider weather episode

A prolonged period of well-below-average spring temperatures combined with an above-average winter snowpack created a dynamic breakup of the Yukon River. This resulted in numerous ice jams and snowmelt flooding on the Yukon River. Breakup flooding began on May 12th in eastern Alaska in Eagle and ended on June 3rd in the Yukon River delta at the Bering Sea coast at the community of Emmonak. The primary cause of this active flood year was a 1-2 week delay in breakup when compared to typical timing. April temperatures were well below normal, and when temperatures began to warm in early May, it melted the low-elevation snowpack quickly. Because of the relatively quick addition of snowmelt onto strong ice, the ice was more susceptible to jamming and floods. In addition to the late breakup, the snowpack this winter was 1 to 1.5 times greater than the climatological normal for interior and western Alaska. Significant ice jams and associated flooding on the Yukon River in Canada resulted in large volumes of ice and water to move down the Yukon River into Alaska.

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Source: NOAA Storm Events Database, event_id 1101989. Narrative written by the NWS forecast office that issued the report.