October 25, 2013


Northwest fog and can be extreme and surprising.  Here are some examples.

(1) The foggiest observing location in the lower-48 states is found at?

Cape Disappointment in Washington State

The North Head lighthouse, north of the western terminus of the Columbia River experiences, on average, 106 days with heavy fog.  (Heavy fog is defined as fog causing visibility to drop below 1/4 mile).
 The location of Cape Disappointment

North Head Lighthouse

Here is a map showing the average number of days with heavy fog each year across the U.S..  Oregon and Washington are not second rate in heavy fog.  Yes, New England and the Appalachians do well on an annual basis, but we in the Northwest have fog more consistently, month to month, then they do!  Tucson is a bad place if you enjoy fog.

(2)  Mosquitoes don't like to fly in fog.  Turns out that that constant impact of little droplets is disconcerting to those buzzing pests (see below).  In fact, fog is more unpleasant for them than rain!  Another reason why the Northwest rarely has a major mosquito problem.

(3)  Fog can create islands in the sky!  Don't believe me?  Check these pictures from Bellevue's Summit neighborhood Thursday morning.  Looks like the San Juan Islands.

Picture Courtesy of Peter Benda

(4)  Fog can flow like water!  Check out this video for the proof!


(5)   The most difficult thing to believe?   The fog period will be over on Sunday as an upper trough comes through.  Here is the upper level (500 hPa) chart for Sunday at 11 AM.  Strong trough!  And we are then on the eastern side of the ridge with lots of flow over us (that is indicated by large number of height lines close together).

Compare that with the situation Friday morning (today) in which we are in the middle of the ridge and the strong flow is way north of us.   You will notice a small low right off our coast that deepened the moist layer on Friday AM.


  1. I believe North Head is also one of the windiest recording locations on the West Coast.

  2. Daddy, daddy, make it STOP!

  3. Fabulous post! Thank you for all the work that you put into this blog. I am constantly quoting it to my friends. (I give you full credit, of course!) :)

  4. Long range GFS has what appears to be the ridge breaking down next week??? YES!!!
    I was almost concerned this was going to go on forever...

  5. I wonder if this explains the mosquito phenomena. During my hiking years the Olympics had only a few. The Cascades could be as bad as the interior of Alaska.

  6. Dang. Since we'd already suffered for quite a while, I was hoping that it would hold on a few more days so we would have a cold but not rainy Halloween evening for trick-or-treating. Oh well, it sure has been interesting, and it's amazing how fast you can get used to and even become blase about almost anything.

  7. Thank you so much for your insights into our crazed "Fogtober". The only other time I've seen fog last like this was during a trip to Germany in the mid 80's, where we experienced solid, thick, all day fog in November for two weeks ... and they considered it unusual for them as well. We drove across a bridge into a wall of fog on our way to a business engagement lasting two weeks deeper in Germany. We didn't see blue sky, sun or even clouds until we drove back out nearly two weeks later. Similar feel to what it's been like here. Nutty stuff. Thanks for "clarifying" what's behind it all.


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