Thursday, November 20, 2008

Another Frontal Passage


Take a look at the radar this morning from Camano Island (see attached). A frontal zone is moving through now with the yellows indicating moderate rain. You will also see the lack of rain to the NE of the Olympics...the old rain shadow.
An infrared satellite picture clearly shows the front and convective clouds (cumulus type) clouds behind it. Those speckled convective clouds are very typical in the NW after frontal passage, producing the "showers and sunbreaks" we all love.
The reason they exist? Cold air over warmer water produces a large change in temperature with height....and that leads to instability and convection. My book describes this process in more detail. These showers will put down perhaps a half foot of snow in the mountains at and above pass level.

So today will be clouds with showers, and we will see a generally dry period tomorrow morning and afternoon until another front comes in around dinner time. Saturday will have some clouds and showers....but Sunday looks very nice. Another weak front on Monday. No major storms next week and Wed and Thursday look exceptional dry and stormless. One of the best end of Novembers in years. This is typically the stormiest period of the year. But forget skiing this month...it won't happen.

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