A Bit Calmer

December 1, 2006

Nice and quiet on the weather set tonight…catching up on emails…looking forward to some sun.  A nice break after a wild November, but I’m sure it’ll get boring in just a few days.

I have a great timelapse coming up at 10pm tonight.  Low clouds sat west of the West Hills Divide all day and late this afternoon they attempted to push up and over into Downtown.  Never made it but an hour’s worth of movement in 8 seconds or so looks really neat from our Tower cam looking DOWN on the clouds.

Showers are all done now and I don’t see any chance for rain until possibly late Monday.  Surface high pressure is building overhead or actually just slightly to our north.  That traps the low level moisture for lots of low clouds/fog overnight.  The big change in the next 24 hours will be the development of a cool low-level airmass in the Columbia Basin of Eastern Washington & N. Central Oregon.  All models develop strong high pressure in the Basin already by tomorrow morning.  UW-MM5 shows 6 millibars from PDX-DLS (or I suppose that would be DLS-PDX = 6mb)…by 4am and then up to 9 millibars by 4pm.   It will not be a widespread "downslope" type wind event though…strictly a Gorge event with the wind dissipating the farther west you go over the metro area.  Don’t expect wind in the "downslope windstorm" spots like Hockinson, Battleground, Sandy etc…

So will it be enough wind to blow away the fog in the middle and west side of town?  I think so since the cool air will also be pretty dry (dewpoints into the 20’s by tomorrow evening at PDX), so even way out in Hillsboro & Wilsonville I expect sun by late afternoon at the latest, just not much wind in those spots.

East wind strengthens in/near the Gorge tomorrow night and Sunday as the inversion overhead really gets going.  A +7 deg at 850 mb on Sunday =  upper 40’s at 4,000′.  But cold air flowing through the Gorge keeps highs near sea-level only in the 30’s.  That’s a recipe for gusts to 70 mph at the west end and 45 mph east of I-205 Sunday, but definitely much weaker west of I-205.  All sunny all of the metro area Sunday with the dry air, but temps shouldn’t get much above 40 with that wind, especially since visible satellite pictures today showed that over half the Columbia Basin is snow-covered…very much like the first couple weeks of early December last year where a chilly airmass just sits to the east and pumps cold air through the Gorge.

A weak system tries to bust through later Monday which kills the wind some and MIGHT give us some rain…if so it would be freezing rain from Corbett/Multnomah Falls east to Cascade Locks, but not in Portland metro area.

More east wind returns immediately following that weak system for Wednesday-Friday next week…Mark

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