Dangerous Black Ice, Fog, and Super-inversion

It's dangerous out there Sunday morning...seriously.

The past few nights we have had increasing ice on our roadways, particularly on the side streets, as frost developed during the evening.

Why frost?  Because ground temperatures are cooling to freezing due to excellent conditions for radiational cooling to space (clear skies, light winds, long nights, relatively moist lower atmosphere from previous rains).

And today something is making it much worse: dense fog, which can cause substantially more roadway icing as the water droplets in the fog freeze on to cold roads.      Here is the view in my neighborhood in NE Seattle:

You can view roadway temperatures on the Seattle SnowWatch site, developed by he UW and the city.  Here is the latest at 8:15 AM (roadway temps are in the boxes).  Freezing (32F) on the University Bridge and one of the West Seattle spans.  Others very close.

As noted in my previous blog, strong and persistent high pressure produces strong inversions around here, particularly in areas within basins and valleys (e.g., Puget Sound, Columbia Basin, river basins), with cold air pooling at lower elevations.   Let me show you the very strong inversion over Seattle Sunday AM (see plot with vertical temperature profiles over NE Seattle between 10 PM Sat to 4 AM Sunday).  An increase of 10C (18F) from sea level to 800 meters above the surface.

With an inversion over us, it was actually warmer at higher elevations yesterday.   Here are the max temperatures on Saturday.  Mid-50s in the mountains, but low forties around the Sound and NW Washington.   Mid-30s around Olympia.

Why so low near Olympia?  Because fog held in all day there (see satellite image on Saturday afternoon)

Today, low fog is extensive over Puget Sound and eastern WA is all fogged in.  The great irony of eastern Washington:  so sunny during the warm part of the year, but a fog bowl during mid-winter, particularly when high pressure is around.

You want to get warmer and see sun?....take a hike to the top of a local peak or head to one of the higher hills east of Seattle.  Here is an photo from Peter Benda, who lives at around 1000 ft on the Eastside.  Nice and sunny up there.

Sick of cold air, fog, and lack of rain?...don't worry.  Everything changes on Monday as we switch back to clouds, warmer temps, and rain.  Normality.

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And don't forget saving our local radio station KPLU.  As I described in previous blogs, we can save KPLU if listeners will tell UW to stop the acquisition and give KPLU a chance to purchase its freedom from PLU.  Why should UW kill a popular local public radio station?