Thursday, December 13, 2012

The Big Snows

Keystone Ridge Weather Station Thursday afternoon
Looks like Fairbanks Airport is going to finish up with a two day snow total of 11.9 inches,
9.5" on Wednesday and 2.4" Thursday (through 3pm).  That's a lot of snow in one storm for Fairbanks. So how often does that happen?

Well, turns out that there are only 24 calendar days in the entire 108 years of Fairbanks weather records with more than 9.5" of snow in a calendar day. Since 1930, the Weather Bureau/NWS era, calendar snowfalls of 9.5" or greater have occurred in just 20 of 83 years. The frequency of a foot of snow in two days is almost identical. So, snowfall like this is something like a one in four year event, though the last occurrence was the freak storm of February 2011.

 Here's the 3am AST Thursday 500mb analysis from Environment Canada: a pattern similar to this, with deep southwest winds aloft  is how we get this kind of heavy precipitation into Fairbanks-land, winter or summer: wrap  oceanic moisture around the Alaska Range.   

Courtesy of Environment Canada

This was not especially close to more than daily record snow. The 24 hour snowfall record for December is 14.7" set in 1968. The all-time 24 hour snowfall record is 20.1" in Febraury1966.

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