Potential for Power Outages Saturday Night/Sunday Morning

Local power companies should organize their supplies and ensure they are fully staffed starting around 6 PM tomorrow (Saturday).

If you live in western Washington, I would charge up your phones and other devices.

A significant blow is coming from a Pacific cyclone making landfall on southern Vancouver Island.

The first strong wind of the season, particularly in October, is always a problem.   There has been substantial growth over the spring/summer that has yet to be tested by strong winds.

Many trees still have leaves, which catch the wind better than the leafless situation later in the winter.

The University of Washington modeling system (WRF) predicts a 986 hPa low-pressure system west of the Washington coast at 10 AM Saturday (see below).   On this chart, the lines of isobars (lines of constant sea-level pressure) and the wind speeds (gusts, knots) are indicated by color shading.  Big pressure changes and strong winds (gusts to 60 kt) are south and west of the low center.

Classic for an ocean cyclone.

As the low moves into southwestern British Columbia, an intense pressure variation (gradient) will move into western Washington (see forecast for 11 PM Saturday night), which will produce strong winds over the region.

The strongest winds so far this autumn.

How strong?  In Seattle, the best way to find out is by going to the City of Seattle Windwatch website (below), which uses multiple weather models to visualize the strong winds over Seattle (below).

Late Saturday and early Sunday, the forecast gusts exceed 40 mph.  My rule of thumb is that early in the season, power outages start with 30 mph gusts and are certain with 40 mph gusts.

Over western Washington, the winds will come in two steps.  

Step one, around 11 PM, will have strong southerly winds (blue colors) from Everett southward (shown below).  

The second act, a few hours later, will have strong westerly (from the west) winds surging eastward in the Strait of Juan de Fuca, hitting NW Washington

Strong southerly winds will also push northward in eastern Washington (wind gusts over the entire state at 2 AM Sunday are shown below)

Puget Sound Energy, Seattle City Light, and other utilities should be ready.

I don't want to hype this event. It is not the Columbus Day storm by any means, but it will have impacts.

Finally, as the low moves past us, air temperatures will cool, and substantial snow is expected in the Cascades.    Snowfall totals through 5 PM Sunday are shown below

The good news in all this is that wildfire season is over in Washington, and our water resources are rapidly growing again. Large amounts of precipitation are being forecast for the next ten days over our region.

Serious storms....midlatitude cyclones...are now predicted

 

Multiple Atmospheric Rivers and Substantial Precipitation

 During the next weeks, a series of potent plumes of moisture (water vapor), commonly known as  atmospheric rivers, will be arriving on the West Coast, and we in the Pacific Northwest will get a substantial taste of it.

Much of the arriving moisture will have traveled thousands of miles from Southeast Asia!

Let me show you forecasts of these atmospheric rivers.  Red colors indicate the most potent areas of water vapor.  At 6 PM tonight (Tuesday), there is an atmospheric river with a tail that extends thousands of miles to the west.

Here is a moisture channel view of the atmospheric river tonight.  You will notice the moisture plume heads northwestward into the Gulf of Alaska, where it circles around a large low-pressure center..  Another stream of moisture is apparent far to the west, starting near SE Asia.  

Thursday morning, another atmospheric river is extending into southwest BC

Next Monday, a potent, intense river will push into north/central California

And the following Friday, a strong river hits the northwest

Still there there on Sunday morning.

These atmospheric rivers will bring lots of precipitation to our region.  Below is the total through Sunday morning.   Our regional mountains get hit pretty hard.  Even more during the next week (not shown).

The latest seasonal forecats are for wetter than normal conditions over the Northwest this winter (see below).  Not surprising for a La Nina year.