Intense Cold Front Brings Heavy Snow and Substantial Precipitation to the Mountains

As predicted, a very strong Pacific cold front moved through the region yesterday, bringing substantial precipitation, including heavy snow in the Cascades. Several mountain observing sites have received over a foot of new snow.

At Crystal Mountain Ski Area, the upper reaches were in white-out conditions this morning:

And the mid-elevations of Alpental in Snoqualmie Pass were a winter wonderland.

The National Weather Service has a Winter Storm Warning for the Cascades and a Frost Warning for the lower slopes:

The visible satellite imagery shows very cold, unstable air approaching the Washington coast (see below)

The white and dark areas offshore show strong cumulus/convective activity resulting from very cold air moving over warm water. This creates a large temperature change in the vertical, which produces convection : small-scale upward and downward motions in the atmosphere.

Upward motion produces clouds and rain, and downward motion creates a clear area.

The radar image last night showed the narrow rainband associated with the intense front (see red arrow). There was also a world-class rain shadow over the North Sound area (light blue arrow).

All of this was nearly perfectly predicted by our models.

Precipitation amounts with the front and trailing showers have been impressive, with the totals through 10AM shown below.

Wow...over three inches in some locations!

Importantly, a persistent Puget Sound Convergence Zone has resulted in heavy precipitation around Snoquamie Pass and the headwaters of the Yakima River (see below)

As a result, there will be plenty of water to fill the Yakima Reservoir system as well as to produce high flows in the entire Yakima river system (see forecast below)

Furthermore, the substantial snowfall will help maintain river flows later in the season.

UPDATE! Snoqualmie Pass has been closed due to heavy snow!

Announcement

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I will hold a special online Zoom session at 10 AM on Saturday for Patreon supporters. Will answer questions and talk more about the recent Sound tornado and about drought issues.