A Major Cyclone Will Approach Our Coast But Not a Repeat of November 19

A very strong, rapidly developing, midlatitude cyclone will approach the Northwest coast on Friday and move through on Saturday.

Fortunately, the wind situation will be far less threatening in the interior compared to the November 9 event.  This blog will explain why.  But big waves may cause problems on the northwest coast.

Let's start with the predicted sea level pressure and surface wind gust map at 10 AM Friday morning.  

Pretty scary looking, with a 979 hPa low-pressure center.  Strong winds (up to 60 knots) will occur in a ring around the low center.  An associated occluded front will be hitting the Oregon coast with even stronger winds at this time.

By 7 PM on Friday the low will move northwestward and strengthen slightly to 977 hPa. 

Overnight the system will weaken and move across northern Vancouver Island.

Importantly, this will change the orientation of the isobars, producing a large north-south pressure difference and strong winds over NW Washington,

Over western Washington, the winds will evolve in three acts.

In the first, shown at 1 PM on Friday, strong winds (blue colors) will occur along the coast and over the waters of NW Washington.  Strong downslope winds will occur on the lee (NE) side of the Olympics. Moderate (20-35 kt) easterly winds will descend the western slopes of the Cascades, but their strength will be NOTHING like November 19th.

In stage two,  shown at 1 AM Saturday, the coastal winds will weaken, although still strong on the northern WA coast.  The downslope easterly winds will have ended and winds will pick up over Puget Sound.

In stage three, northern Puget Sound winds (from roughly Seattle to Bellingham) will strengthen with gusts reaching 30-40 knots from the Sound.   A few branches may fall and I expect a few minor power outages.  Nothing significant.  Winds will fade later in the day

This event will represent a typical mid-winter blow.

The most serious impacts may be the waves and high water levels on the Washington Coast.

The strong winds acting on the Pacific should produce substantial wave action on our coast and Vancouver Island.  The latest NOAA WaveWatch3 prediction is for significant wave heights of 20-30 ft.

That will be on top of some higher-than-normal astronomical tides (see below for La Push/Quilayute):

Clearly, some potential for coastal flooding on the northern Washington coast late Friday and Saturday.