Thursday, December 25, 2008
I sit here, watching large snowflakes fall in the darkness outside my window. This is the last snow day in the lowlands for a while I suspect.
The radar shows the story (see image): moderate to heavy precipitation north of Seattle that is bringing wet snow, with some rain in warm locations near water. Outside my house it is collecting in a slushy layer, but some of the WSDOT cams show accumulation on some roads.
This precipitation is associated with an upper level trough over the region...which will move out later today. You can see the clouds associated with this precipitation on the latest infrared satellite photo (see image)--the roughly east-west band over the northern portion of the state. And there is nice low circulation off northern Oregon. These showers will lessen during the day,
The big change is going to occur later tomorrow and Saturday. The atmosphere is about to radically reorganize itself. For nearly two weeks we have had a large scale configuration with a big ridge (high pressure) over the eastern Pacific and northerly, cold flow moving southward into our area (see figure). But that will change...the flow will become more east-west ("zonal" in the business) and that will bring in much warmer and moister air (see figure). That means a return to our familiar rains late Friday and Saturday. By late Saturday I suspect most roads will again be passable.
Hopefully, the last week has taught us something about future preparations for ice and snow and rational changes will be made in how we deal with it. We narrowly avoided a terrible tragedy, with two buses nearly falling on to I5--clearly there would have been serious injuries and deaths if it had. Anyway, this will be my last editorial on this issue!
Posted by Cliff Mass at 7:07 AM