Monday, January 10, 2011

Afternoon Update

Well, the models continue to push the low pressure system further north than previously forecasted which is better for us, unless you were hoping for the snow. It is getting harder and harder to get snow down to the lowland levels, and for the higher elevations and over into Portland, in addition to the snow as a concern, this would lend itself to a greater chance of freezing rain after a brief period of snow. So with all that said, it is now shaping up to look something like this – the rain should now start sometime between 2-4pm tomorrow. After the sun goes down, the temperature drops and we may see periods of a rain/snow mix until around 10pm. After 10pm it gets even trickier as the potential for freezing rain goes up until around 4am Wednesday. Tomorrow’s low is currently forecasted to be 33. Let’s assume this is correct, or it could be even a few degrees warmer. There are areas in the county that we know are always nearly 5 degrees cooler than everywhere else. This would put them at freezing and in these areas black ice would be of concern. After that the warm front would push out the colder temperatures and we would have rain only. Obviously is we had areas of ice, it would still be present for a period after the transition to rain. The only other thing worth mentioning is the winds. During the evening and early morning hours as the low tracks close to the coast, and the warm front pushes through, the winds along the coast could be 35 gusting to 50-60 for a period. As I type this the NWS Portland has issued a High Wind Watch for the north and central coast for south winds 30-40 gusting to 60 at the beaches ands highlands. This should be followed shortly by a Gale watch or Warning for the waters as well.

That takes care of the lowlands, now let’s talk higher elevations and the passes. There may still be a Winter Storm Watch issued later for the Coast Range. I would expect the snow to start there by 4pm tomorrow and continue until transitioning to freezing rain after around 10pm. This will continue until around 4am when the temperatures warm up and the freezing level rises to above the pass level. Overall the passes should see a trace of snow starting at the lower levels to 1-2” at the top of the pass before switching over to freezing rain. The forecast for accumulation of ice at the upper levels is 2-4 tenths of an inch.

I can’t type fast enough! The NWS has just issued the Winter Storm Watch for the Coast Range effective from Tuesday afternoon thru late Tuesday night. For those that also receive my Nixle alerts, they will follow shortly.

If your travel plans include the valley Tuesday or Wednesday, they are looking at snow starting between 2-4pm tomorrow, then transitioning to freezing rain at 10pm which switches to all rain by 4am Wednesday. Tomorrow commute could be a lot of fun for a lot of folks over there! And the Cascades and their passes, a foot of snow and ½” of ice Tuesday and Wednesday….not fun!

Next update – tomorrow morning…

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