Friday, December 17, 2010

TGIF

I see blue sky now as high pressure moves across the area. The higher passes are still reporting temperatures below freezing so if you have travel plans into the valley, watch for patches of black ice as you cross the area of the summit on Highways 6 and 26. They also have a dense fog advisory for the valley until 10am this morning. As for us, the high pressure will move east today as a large area of low pressure continues to develop in the northeast Pacific which will allow disturbances to rotate under the low and into our area through the weekend and into next week. The next disturbance will move in tonight and tomorrow morning and could bring snow to the upper levels of the passes once again by tomorrow morning. There is also some concern that with the cold air moving into the valley from the Gorge area that some of the low elevation snow expected in the Columbia River Gorge area tomorrow morning may make it into the Portland/Vancouver area. Should the Portland/Vancouver area get the morning snow or rain/snow mix, it will turn over to all rain in the afternoon. If you are traveling through the Gorge area, it will likely be snow all day Saturday. If you are traveling through those areas, watch the weather carefully before you go and be careful.

Well, that takes care of today and Saturday morning…starting Saturday afternoon, watch for rainshowers and possible thunderstorms again through Sunday. As for next week, more unsettled weather as disturbances continue to rotate under the low and through our area for most of next week.

After the Aumsville Tornado this week, I did a little research…it appears Tillamook had a F1 tornado (86-110mph winds) touch down at 9:30pm, December 12, 1975 that stayed on the ground for approximately 2 miles and caused considerable damage. It reportedly passed by KTIL radio which recorded 90 mph winds as it passed. Overall, from what I could find, Oregon has an average of 2 tornados a year, putting us about 47th in the nation, Texas leads the race with over a hundred, followed by Oklahoma, Florida and Kansas. Also, you’ve heard much talk about the Fujita Scale (also known as the Fujita-Pearson Scale) this week. This is determined after examining several factors related to observed types and extents of damage. Here is a little about that scale.


EF0 weak 65-85 Gale
EF1 weak 86-110 Moderate
EF2 strong 111-135 Significant
EF3 strong 136-165 Severe
EF4 violent 166-200 Devastating
EF5 violent > 200 Incredible

Gordon

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