Tuesday, February 10, 2009
The major act of this play is now beginning. So far the models have done a splendid job. As predicted southeasterly flow developed, with downslope on the western slopes of the Cascades causing drying and upslope on the SW of Olympics forcing some moderate to heavy snow. Look at the radar...you can see the large gradient of precipitation and the heavy snow over the Kitsap. Shelton is reporting very heavy snow right now...and one of our correspondents has 4 " on the ground near the Hood Canal at 500 ft. And they are going to get a lot more.
The main front is now making landfall (see high res satellite picture). As a result, precipitation intensities will increase over the interior of western Washington--and it has been snowing along the coast all morning from it. The big question is temperature...can they stay low enough to maintain the snow and for how long--since temperatures will be increasing aloft due to the warm front. Some insight into the temp structure aloft is available from the Seattle profiler (see image). When you look at the temperatures, subtract 1C...since it is showing something slightly different than temperature (virtual temperature). The freezing level has risen to about 400 meters (1300 ft), with a snow level of roughly 300 ft. But that will come down quickly when real precipitation starts. In fact, snow has already begun in earnest at Olympia (see image), with light snow spread to Sea Tac. Fortunately, the temps are above freezing and the roads are relatively warm...so the snow should not stick well on busy hiways.
Posted by Cliff Mass at 12:00 PM