Historic heat wave melts out 30% of Mt. Rainier area snowpack in 4 days

What La Nina gave, historic heat wave took much of it away…

As the winter season neared an end, mountain snowpacks were still running a decent amount above average. Then temperatures soared into the 80s, 90s -- even triple digits -- in the higher elevations of the Cascades and the snow didn't stand a chance.

Snow depth gauges at Paradise Ranger Station around 5,400 feet up Mt. Rainier measured 106 inches of snow on the ground on June 6, according to the Northwest Avalanche Center. A month later on July 5, there were a scant 8 inches up there.

Summer melting of the snowpack is indeed an annual occurrence but the National Weather Service in Seattle says 30% of that meltoff came in the four days between June 26 and June 30. Paradise reached the upper 80s on June 28 and then hit 91 degrees on June 29.

Freezing levels then were higher than any mountain in the region, reaching as high as 18,200 feet. All that heat meant a lot of snowmelt and a lot of mountain runoff into our local waterways. 

Sediment flows into Puget Sound from the Puyallup River on June 30, 2021. (Image courtesy: Sentinel Hub EO Browser with contributions by ESA)

Still, even with the big loss of snowpack, La Nina was strong enough to keep Mt. Rainier's snow up there to pretty close to a typical year. The mean meltout date at Paradise is July 11, according to University of Washington research meteorologist Mark Albright, though that date has drifted back to July 13 if you factor in the past 40 years. Last year, Paradise didn't melt out until July 21, Albright said.

RELATED: June ends up 2nd-hottest on record in Seattle

Paradise has melted out as early as May 24 in 1941 and as late as August 25 in 1974 – a date that was challenged 10 years ago as Paradise melted out on Aug. 24 in 2011.



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