Push Underway

May 5, 2006

Big marine push underway West of the Cascades this evening (as expected).  North Bend to Spokane gradient has gone from -2.5 mb. yesterday evening to +10 mb. this evening!  A shortwave trough in the upper atmosphere is sliding by just to the north, initiating the onshore surge of marine air.  I notice KLS already has a patch or two of low clouds at 9pm, so it shouldn’t be hard to fill in the whole Willamette Valley before daybreak.  MM5 cross-section shows the moisture up above 850mb by morning, so it’s going to be a very deep layer of marine air.  Instead of 76 tomorrow, we’ll only hit the low-mid 60’s.   One thing that could give us a few sunbreaks in the afternoon is that the upper atmosphere is going to cool off quite a bit too.  That lessens the marine inversion enough that breaks may form in the cloud cover.  We may escape without a solidly cloudy day.

Then a cold front slides through Sunday, which should be a very chilly & somewhat wet day.  The trough behind comes in Monday, then back to ridging and June-like weather next week.  Long range models are waffling on the strength of the ridging Wednesday-Friday.  Some have a vigorous wave coming through Friday for a quick cooldown.