February 20, 2013

Weather Returns to the Northwest

I knew it was a mistake to blog about boring weather....

For those of us who have forgotten what Northwest weather can bring, we are about to get a reminder.

But before I talk about that, let me invite you to the Northwest Weather Workshop, which will be taking place in a little over a week (March 1-2).  This is the big local meeting for those interested in Northwest weather, with a wide variety of talks, most of which are accessible to those who don't have a formal meteorological background.  It starts at 1 PM on Friday, March 1 and ends Saturday around 3 PM.  We have a very nice banquet at Talaris Conference Center in Seattle, with a special speaker (Susan Joslyn, a UW psychology professor who specializes in how weather information is communicated.)   More information is found here.   You need to register if you would like to go!

 Now the coming weather...

The upper level ridge that has been over or just east of us has faded and strong flow from the west is now headed towards are region.  To illustrate, here is the  upper level (500 hPa, roughly 18,000 ft) flow (solid lines are the heights of the 500 hPa pressure surface) for Friday morning.  Winds are nearly parallel to the lines and are stronger when the lines are closer together.  A series of disturbances is lined up to move into our region.

In concert with the approaching disturbances, this strong incoming flow (also known as the jet stream) will be bringing a current of high amounts of moisture, moisture that was injected northward over the western Pacific.  Here is the forecast moisture distribution on Friday morning.  Red indicates high values.

Expect plenty of rain and snow.  Here are the total precipitation and snowfall for the 72 hr beginning Wed. morning at 4 AM.  2-5 inches on the western slopes over most the windward (western) slopes of the coastal and Cascade Mountains.   Yes...not a record atmospheric river...but a good soaker.

Temperatures will be cool enough that a lot of this precipitation will be snow in the mountains.  We are talking about 2-3 feet of snow, particularly above roughly 3500 ft.

And winds?  Expect strong winds over the eastern Pacific and Northwest Washington on Friday as a strong low moves to our north.  (see map of sustained winds below).  30 kts plus sustained winds along and off the coast. Considerably stronger gusts.

And you like waves?  With a strong weather system on Friday and powerful NW winds behind, there will be substantial waves on the ocean beaches (see graphic valid Saturday morning).  Yellow indicate waves of 8-9 meters, 25-30 ft.   Good wave watching on Saturday afternoon at Westport.

So enjoy the active weather...nothing that will cause a lot of damage, but enough to remain us that Northwest weather can be fun.


  1. If you are a kitesurfer this is the kind of weather that makes Seattle feel like a resort destination!

  2. Ah, March weather arrives early.

  3. Will be nice to get some precip here east of the mountains. It's dry. Too dry really. The 8-10 day European model has a big ridge over the west again so let's enjoy a change before we potentially go back to boring ... or dare I say springlike!

  4. Hey Cliff, I know it is not exactly relevant to today's discussion, but can you tell us more about the Madden-Julian Oscillation sometime???? Thx!

  5. So what percent of our total precip comes from these few events?

    What effect will a warming climate have on the # and strength of these warm fronts?


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