The National Weather Service is predicting high winds from 1pm on Tuesday  through 1am on Wednesday and issued a High Wind Warning. They are predicting gusts up to 55 mph which is likely to cause power outages. Officials recommend that you charge all batteries, Ready.gov offers a comprehensive look at what to do to be prepared. 

https://www.ready.gov/sites/default/files/2020-03/power-outage_information-sheet.pdf

In brief they say:

• Keep freezers and refrigerators closed.
• Only use generators outdoors and away from windows.
• Do not use a gas stove to heat your home.
• Disconnect appliances and electronics to avoid damage from electrical surges.
• Use alternate plans for refrigerating medicines or power- dependent medical devices.
• If safe, go to an alternate location for heat or cooling.
• Check on neighbors.

HIGH WIND WARNING IN EFFECT FROM 1 PM THIS AFTERNOON TO 1 AM PST WEDNESDAY

* WHAT...Southwest winds 30 to 40 mph with gusts up to 55 mph expected.

* WHERE...Southwest Interior, Tacoma Area, Seattle and Vicinity and Bremerton and Vicinity.

* WHEN...From 1 PM this afternoon to 1 AM PST Wednesday.

* IMPACTS...Damaging winds will blow down trees and power lines. Widespread power outages are expected. Travel will be difficult, especially for high profile vehicles.

* ADDITIONAL DETAILS...Saturated soils from recent precipitation will make it easier for trees to come down.

PRECAUTIONARY/PREPAREDNESS ACTIONS... People should avoid being outside in forested areas and around trees and branches. If possible, remain in the lower levels of your home during the windstorm, and avoid windows. Use caution if you must drive.

Why does Seattle suffer so many power outages?

The Seattle Office of Emergency Management published a document about this called

Seattle Hazard Identification and Vulnerability Analysis

in which they note:

About half of Seattle City Light’s unplanned power outages are caused by falling trees or branches.

History

All power systems experience unplanned outages. Most are small, resolved within a few hours and do no lasting damage. Larger outages occasionally occur. These outages are usually secondary events caused by other hazards, e.g., winter storms. Some larger outages, such as the 2003 outage, demonstrated that power outages can be a primary incident. Two local examples are two fires in underground vaults serving the downtown areas that caused lengthy outages. This section lists major outages in Seattle and several regional events that did not directly affect Seattle but highlight issues with the Western power grid.

1958. Seattle. Wind related outages. Loss of power in many areas of the city, especially in West Seattle and Magnolia.

1962. Seattle. Columbus Day Storm. Biggest storm to hit the Pacific Northwest. It affected utilities throughout the region.

1988. Downtown Seattle Vault fire. Six electrical cables were damaged resulting in a four-day loss of power to a 50 block area in downtown. The area included the Westin Hotel and the Pike Place Market. The cause was a contractor driving a steel piling through a buried cable. Businesses that lost power sued the city and the contractor. Newspaper reports that the city paid more than $1.5 million to settle claims.

1993. Downtown Seattle Vault fire on October 5th. 1,800 customers in about 270 buildings were out of power for up to three days in 37 block area. Eight large generators were brought in to help the population. Fire destroyed huge underground cables that had to be replaced.

1996. Western Interconnection. Two major outages struck the Western power grid in 1996. On July 2, a localized outage caused by a tree in Idaho led to a cascading regional outage that resulted in 10% of the consumers in the western U.S. losing their power for at least a few minutes. The next month, on August 10, more than 7 million people across the West lost power. Areas were affected intermittently for up to several hours.

1997. Western Interconnection. Two separate disturbances in the Western grid that interconnects with Seattle City Light’s system. Both outages had minor customer impact but could have been worse.

2000 – 2001. California. Rolling blackouts plagued much of California. The Northwest was involved as a power supplier. This event placed strain on transmission lines in the Northwest and caused two major outages during peak demand periods.

2006. Seattle. Seattle City Light suffered its most extensive outages in the utility’s history as a result of a severe regional windstorm. More than 49% of customers lost power. Some customers were without power for more than a week. Neighboring utilities were also suffered major damage.

July 2009. Western Washington. While Seattle avoided power outages during record heat, Tacoma and Monroe did not. Typically, summer is a low demand time for Pacific Northwest power but this event demonstrated that Seattle is also vulnerable to demand spikes during the summer.

Likelihood of Future Occurrences

No system is 100% reliable. The costs of such a system would be prohibitive even if possible. Seattle will have major unplanned outages in the future. The more important questions are how frequent will these outages be, how many customers will they affect and how long will they last?

Wind will continue to be a hazard to power transmission. Although it has fewer trees that the rest of the county, Seattle is attempting to re-grow its tree canopy. Seattle City Light has increased its tree trimming program, but it is still possible that the number of tree-related outage could increase.