By July in a typical year, the snow that covers the slopes of the Rocky
Mountains has given way to grasses and wildflowers, leaving only the peaks
capped in white. But 2011 has not been a typical year. As this image of the
Mountains in northeast Utah shows, winter’s snow is lingering into
summer. On June 26, the snowpack on the southern face of the range was 849 percent above average. The northern face had 892 percent more snow than average.
The image was taken by the Landsat 5 satellite on July 15, 2011. The
lower image, also from the Landsat 5 satellite, shows more representative
conditions on July 9, 2003. In the lower image, snow snakes along the high
ridgelines, while the slopes are bare. Snow is a much more dominant part of
the scene in 2011.
The Uintas are typical of conditions throughout the northern Rockies and
northwestern United States. From Montana to California, the extent of
lingering snow is “exceptionally unusual,” said the National
Climate and Water Center, who reports that snowmelt is usually complete
A cool spring is part of the reason that the western mountains
still hold snow in July. Washington and Oregon experienced the coldest April
to June on record, and other western states experienced temperatures below
or much below normal. With low temperatures, mountain snow didn’t melt
The other reason the snowpack is lasting into summer is that there was
more snow to melt. The winter and spring of 2010-2011 brought far more snow
than average, leading to a record mountain snowpack in at least five states.
A healthy snowpack is a boon to western states most of time. Snow stores
water for use in the dry summer months. However, if the snow melts quickly,
the runoff could cause floods. Already, melting snow
contributed to flooding
in the Missouri River basin. As the snow
melts in other basins, it could swell rivers with unseasonal floods.
Despite the record snow in some western states, the snow extent in North
America as a whole was below average in the spring (March to May) for the eighth
year in a row. The extent was low because less snow fell in central and
northwestern Canada and Alaska than average.