Hot Weather Update

May 12, 2006

I seem to have a bit more free time tonight (sunny weekend forecast), so here’s a little early blogging for your Friday evening.

The last of the clouds are dissipating across NW Oregon & SW Washington this evening as onshore flow weakens.  I notice the North Bend-Spokane gradient has been decreasing today, and should go "offshore" or easterly tomorrow.  As the big western U.S. upper-level ridge builds the next 3 days, we get a warming trend each of those days.  Tomorrow and Sunday we’ll have a gradual warming.

No changes in the Monday thinking.  All models combine a +19 to +21 deg. C. 850mb temp over NW Oregon with strong easterly flow the entire day.  My chart gives us a 95 deg. high at PDX if everything stays the same.  Of course any cloud cover from the south or TOO much easterly wind could easily keep it a bit cooler, so that’s how I arrived at the 93 in the 7 Day forecast.

Even more interesting to me is the instability later Monday through Tuesday AM as a shortwave trough "nicks" us.  It’ll be rotating around the big upper-level low sitting offshore.  This is a classic setup for evening or overnight T’storms over and WEST of the Cascades.  CAPE on the 12z ETA jumps to 1800 and lifted index is way below zero.  Very impressive for us.  IF we get moisture, evening/overnight lightning is very likely.   That also is accompanied by a brief but strong marine push, so a big cooldown Tuesday, but flow already turns offshore again by Wednesday as the big ridge overhead holds strong.

A similar setup maybe next Thursday could give us another thunder threat….enjoy the sunshine this weekend…Mark