Let
it snow, let it snow, let it snow
By Greg Berman
The
Cascade Mountains are notorious for some of the largest
average snowfall totals in the world. Mt. Baker, located
a scant 60 miles from Bellingham, has an average of 650 inches
of snow per season, the largest total for any recording station
in North America. And most Cascade ski areas receive over
400 inches of snow per winter. Then why is it powder-buffs
still sweat it out every year, wondering whether their favorite
ski resort will recieve the necessary base for a great snow
season? The answer is more complicated than one might realize.
The difference between a banner year and a bummer year hinges
not only on localized weather systems, but also on long-term
weather patterns that either signal season-long problems
as we saw in 2004-2005 or create a bevy of snow like no other
mountain in the world.
Mt.
Baker has the distinction of relying solely on Mother Nature’s
natural snow-making machine, unlike their mountain range
cousins in Colorado that only need a button pushed to turn
their brown spots into bright white. According to Gwyn
Howat, Mt. Baker Ski Area spokeswoman, the ski area doesn’t
need a snow-making machine “due
to the plethora of snow that falls each winter.” Howat
says “the
problem is temperature, not precipitation.” Even
last winter, which was supposed to be a down moisture year,
Baker still received 497 inches, but there were “definitely
temperature issues that caused several periods of rain
on an otherwise great snow base.” The localized and
season-long weather patterns have a direct bearing on the
temperatures at Baker and the Cascades, and these patterns
can decide the success or failure for each of the Cascade
ski resorts.
The
localized weather patterns during normal winters usually
bring the necessary cold air and moisture to the Cascade
Mountains. Forecasters look for a ridge of high pressure
around a hundred miles off the northwest Pacific Coast.
Then a nice juicy low pressure system needs to set up along
Washington’s
coast, extending to just west of Vancouver B.C. The clockwise
circulation around the high brings Pacific moisture directly
into the Cascades. The low pressure system, with its
counterclockwise circulation, scoops up the necessary cold
air from British Columbia and dumps it over the Cascades.
The jet stream or storm track will ride down the west side
of the low, and this will help drive cold impulses into
the mountains. This one-two pressure punch, in a typical
season, usually sets up every three to days, thus leading
to some of the highest average mountain snowfall totals
in the world.
The
question then begs, what type of weather pattern creates
a season-long snow-buster as we saw during the 2004-2005
ski season? That would be two dirty words on the lips of
ski resorts: El Nino. El Nino is a marked warming of the
tropical Pacific Ocean from the International Date Line
eastward to the northwestern coast of South America. How
does this affect the Pacific Northwest when this phenomenon
is so far away? This warm pool of water gives birth to
strong low pressure systems that help split the jet stream
across the U.S. This split causes strong storms to blast
the southwestern U.S. On the flip side, with the southern
jet stream doing its damage across the southwest and southern
U.S., the northern jet stream spends much of the winter
camping out in Canada, leaving the Pacific Northwest out
of the winter storm party. Although moisture can still
sneak into the state from the Pacific, the necessary cold
air for snowfall is hung up in British Columbia for much
of the El Nino winter.
La Nina,
another season-long weather pattern, has just the opposite
effect. In this scenario, the tropical Pacific waters are
colder than normal. This helps to pull the icy northern
jet stream further to the south, since the southern jet
is usually non-existent during these winters.
Colder
than normal winters usually smack the Cascades, and this
means much above average snow years. In 1998-1999, Mt.
Baker busted the seasonal snow record with almost 1,200
inches of snow, and the pat on the back for that one goes
to La Nina.
A recently
discovered weather pattern that lasts much longer than
El Nino and La Nina is the Pacific Decadal Oscillation
(PDO). This phenomenon also depends on warming or cooling
of the tropical waters just north of the equator, but the
pattern is in 20 to 30 year chunks. During the cooler water
phase, the northern jet stream is in a favorable position
to keep the Alaskan cold air express pouring over the Cascades.
There are indications the PDO is going into a cooling phase,
and if the research is correct, this could bode well for
the Cascades over the next two decades.
What does all this mean for Mt. Baker? After months of
research, there is no clear sign of El Nino or La Nina.
This leaves the Cascades in an in-between year, and during
these years, the mountains usually experience much above
normal snow-fall totals. And, if the Pacific Decadal Oscillation
theory pans out, Mother Nature may not switch off her snow-making
machine for another 20 to 30 ski seasons.
One
can only hope! So let it snow and snow and … well,
you get the picture. |
ARCHIVES
