15" of snow falls in 90 minutes

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A strong storm caused by the giant kink in the upper level jet stream just produced one of the largest snowfall rates every seen in the United States; 10 inches an hour. 

Imagine walking into the grocery store when there wasn’t a flake of snow on the ground, and then walking out an hour later with your car buried in nearly a foot of snow.  That’s what just happened to in Thompson Pass Alaska.  Sitting just outside the very popular tourist spot of Valdez on the edge of the southeastern Alaska mountain range, the area just experienced something that few will ever witness and has rarely occurred, even in Alaska.

Thompson Pass received 40 inches of snow in half a day, just 12 hours total, with 15 inches of that snow falling in just 90 minutes.

Thompson Pass Alaska is no stranger to heavy snow as it sits along the coastal Chugach Mountain range, near the cove of the very popular Prince William Sound, home to one of the few coastal glaciers that can be seen from a cruise ship.  The pass is the snowiest reporting station in the country, getting more than 600 inches of snow a year on average, but has recorded more than a thousand inches of snow several times.  Even though the area is used to heavy snow, the rate this storm was producing was far beyond what even these mountains typically see. In comparison, the Twin Cities averages about 54” of snow a year.  Even Yellowstone National Park, home to one of the snowiest cities in the Lower 48, averages about 400” a year… significantly less than Thompson Pass.

The intense snow was produced by an atmospheric river.  The term describes a phenomenon in the Pacific Ocean where high winds at the mid and upper levels of the atmosphere can draw in huge amounts of moisture from the tropical regions northward toward the poles.  This is how California gets 90% of its moisture.  While fairly common along the West Coast of the U.S., they rarely push so far north.  The kink in the North American jet stream had a lot to do with why it was able to get so far north.

The city of Valdez and Thompson Pass are now cutoff from the outside world as the only highway in and out was buried in an avalanche.  The Alaska Department of Transportation said it could be a couple of weeks before the road is able to reopen, weather permitting of course.

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