Strong winds blew past and downstream gaps in the Cascades and other mountain barriers in the region.
Consider the strongest winds observed this morning (see below).
There are three gusts exceeding 40 mph (yellow). One extends southwest of Bellingham and passes through the San Juan Islands and then goes west out into the strait.
The other extends northwest of Mount Rainer and out to Tacoma. And another extends from the Rivr Canyon west of Columbia and then through Portland and the Willamette Valley north.
There were some unusually strong winds over some exposed ridges, like one near the Tri-Cities.
What is going on here?
We start with the huge difference in pressure across the Cascades. Sea level pressure (solid line) and near-surface temperature (colored, blue and purple indicate cold air) at 4 a.m. this morning are shown.
There is a very large pressure difference (slope) on the Cascades with higher pressure in the east. Cold air is denser than warm air, resulting in higher pressure near the eastern surface of the Cascades.
This difference in pressure creates wind, which accelerates from high pressure to low pressure.
But there’s a problem. Cascades block the air at low levels!
Thus, the air looks for gaps or weak points in the Cascades to overcome, and as shown in the topographic map below, there are three of them.
A void surrounds the Fraser River Valley and exits near Bellingham. Another is the Columbia River Gorge, a distance close to sea level on the Cascades. And the last one is the Stampede Gap southeast of Seattle, which represents a weak point or lower area in the Cascades.
These three gaps represent favorable conduits for pushing air westward from eastern Washington.
An exciting development is the growing ability to skillfully predict strong cleft winds using high-resolution zonal models.
To illustrate, below is the 24-hour forecast for winds exiting the Fraser River cleft at 4 a.m. this morning. You can see strong winds blowing through Bellingham and the San Juans.
Finally, there’s the issue of hole travel. Where is the best place to experience regional crevices?
My recommendation is Crown Point in Columbia Gorge, with Vista House being the perfect location. They even have a snack bar!
Winds have reached more than 100 mph at the site. This morning it went up to 74 mph.
