Cold and Frost

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For many Northwest residents this morning was the coldest by far this fall, with some western lowland locations dropping into the lower 20s.   Frost is widespread and in some places fog is laying down a formidable coating of ice.  "Black ice" season has begun.

Take a look at the temperatures on both sides of the Cascades for the past four weeks at Spokane, Sea-Tac, Olympia and Pasco--today is the coldest for all of them, with cold air aloft, few high clouds , and relatively light winds.. This combination allows the surface to radiate heat to space without a lot of mixing of warmer air down from above.
Here are the 24-h minimum temperatures ending at 7 AM Saturday.  Quite a range...low 40s near the water, lots of 20s in the western Washington interior, with Olympia getting down to 21F (and you though Olympia was full of hot air!).  Some teens and single digits in the mountains, and 20s in eastern Washington.


But the coldest regional temperatures in this kind of situation are usually in the valleys over the uplands of eastern Oregon.  Here is the proof (only showed temps below 20F).  Teens are nothing there and several locations had single digits.


Today will be a cool day (highs in the mid-40s) and many of you will see some sun as the fog and low clouds burn off.  Unfortunately, the next weather system is moving in more quickly than expected a few days ago, with rain hitting the coast early Sunday and reaching the western interior by roughly 1-2 PM that afternoon (see graphic)--so enjoy the outdoors today.  It will be perfect weather for raking leaves (my task this morning!)

Forecast precipitation for the 3-h period ending 1 PM Sunday. Note that "cin" means hundredths of an inch (32 is .32 inches in 3 hour)

 Let me end this blog on a personal note.  Yesterday, Amy Bell of the Technology Alliance reminded me that Friday was Carl Sagan Day (see graphic).   Many of you know about him--he was not only one of the nation's leading astronomers, but perhaps the most effective communicator of the excitement and importance of science of the past fifty years. 

What you might not know is that this blog would surely not have existed without him.  I was an undergraduate at Cornell and was really interested in both astronomy and meteorology.  Sagan took me under his wings and we worked together on a model of the Martian atmosphere (my first publication).   He impressed on me the need and importance for scientists to communicate directly with the public: that this is an essential requirement if science and society are to flourish.  His impact on me was profound and this blog and my work at KPLU is an outgrowth of this influence.  Sagan was not afraid to talk about the societal implications of his research, be it about the sustainability of our planet, the potential for nuclear winter, or the need for a scientifically literate population. When KUOW's Steve Scher gave me an ultimatum that I could only talk about weather on his Weekday program, and never about science/math education and the implications of my science, I thought of Sagan and knew what he would counsel.  Better to be kicked off KUOW then compromise important principles.

Sagan is surely missed, but his influence and importance continues today.

Carl Sagan and me on my graduation day.  I look a bit younger!