The weather in Puget Sound is affected by the land, water, mountains
and rivers of the Pacific Northwest. It is important to understand
the different features to understand the weather.
In British Columbia,
which is the province of Canada directly north of
Washington,
there are two main mountain ranges. The
Canadian Coastal Range
is a range of mountains running from northwest to southeast
right on the west coast of British Columbia (55N 130W to 50N 123W). The
Rockies run from northwest to
southeast along the Alberta border (55N
123W to 49N 114W). Along the Canada - United States boarder there is
another area of mountains called the
Okanogan Highlands (between 48N
and 52N) that runs from the Canadian Coastal Range to the Rockies. There is
one main river that cuts through from the interior of British Columbia
to the Pacific Ocean, the Fraser
River which reaches the ocean at 49N 123W.
In Washington, the Cascade Range runs north to south from 49N 122W to 42N 123W. The Coastal Range runs along the coast from 43N 124W to 47N 124W, ending in the north with the Olympic mountains on the Olympic Peninsula in Washington. The Columbia River cuts through both the Cascades and the Coast Range at the Washington - Oregon boarder. There is a gap in the Coastal Range at 47N called the Chehalis Gap where the Chelais River runs into the Pacific. The waterway connecting Puget Sound to the Ocean is called the Strait of Juan de Fuca. It runs north of the Olympic Mountains and south of Vancouver Island. Here are some outline maps:
Here are some false color terrain maps where the ocean (sea level) is blue, low areas are green and high areas are brown:
The terrain that affects snow events in Puget Sound in mainly the
mountains in British Columbia and the Fraser river. Cold arctic air
forms over the Yukon in the winter. This air is dense, and thus has a
higher pressure than the surrounding air. Occasionally the air move
south and is trapped in the "bowl"
formed by the Canadian Coastal
Range, the Rockies and the Okanogan Highlands.
Since the cold air has
a higher pressure, and since air moves to lower pressure, the cold air
will flow through gaps in the mountains
(see exercise). These gaps
usually contain rivers. The gap that affects the Puget Sound is the
Fraser River just across the border
in Canada.
The cold air flows
past Hope, B.C. and Bellingham Washington and into the Puget Sound
region.
During such an event, Bellingham will have a strong, cold
wind out of the east or northeast.
