Russ Steele
There is a lot of Global Warming on the ground through out the west. A guest post on Watts Up With That has a rundown on the the western snow pack. "May snow depths are deeper than anything we have seen in the last 45 years" in the Tetons. Here is a link to a report on the Washington/Cascade Snow Pack.
Is snow in May at Lake Tahoe unusual? Looking at the 107 year record it snowed an inch or more in May 44 years out of 107, or 41 percent of the time. The average depth is 3.7 inches, how ever there were some block buster springs:
1912 - 20 in
1933 - 16.5 in
1950 - 21 in
1953 - 16 in
1964 - 33.5 in
1977 - 16.5 in