Stevens Pass snow melt-out climatology

As the Stevens Pass snowpack drops to 100 inches today (13 May 2011) for the first time since 9 March it is a good time to take a look at the climatology of snowpack
melt out at Stevens Pass in Washington’s Cascade Mtns.

I have compiled the melt out dates observed at the Stevens Pass Snotel site. Melt out date is defined as the last day with 2 inches or more of snow water equivalent (SWE).

There now are 30 years of record from Stevens Pass extending over the years 1981-2010.

Earliest melt out was 1 May 2005.
Latest melt out was 25 June 2008 and 25 June 1999.
Median melt out date over 1981-2010: 1 or 2 June
Mean melt out date over 1981-2010: 31 May or 1 June

Mean melt out dates by decade showing a tendency towards later
melt out dates in recent years as our Pacific Northwest climate has
cooled since 1990:

1980s:   30 May
1990s:    1 June
2000s:    2 June
2006-10: 10 June
2010:    10 June

Even though the mid-winter snowpack was below normal in 2010, the melt out at Stevens Pass was about 9 days later than the 30-year mean due to a cool spring in 2010.

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