Record Cold Day

May 4, 2010

How rude, I said I would write more last night then realized on the way home I never did.

We broke a daily record low maximum here in Portland (and Hillsboro) today.  It appears to be the coldest May day since 2000 as well.  Brrr!  It was all about the sunbreaks and it appears PDX had enough cloud cover, and obviously a cold enough airmass to keep that temperature down.  Yevgeniy, our current weather intern, has just recently updated our May “magic chart” for forecasting high temps in the warm season here in Portland.  Our chart now covers 00z Salem soundings from 1997-2009.  Up UNTIL TODAY, the coldest 00z 850mb temp at SLE in the month of May since at least 1997 was -3.2 deg.  Well, this afternoon it was -3.5.  So this afternoon we saw the coldest 5000 ft. (about) temperature we’ve seen since at least 1997.  We hit the bottom of the chart!  It’s only uphill from here on on out baby!  Speaking of that two things to talk about this evening…convection tomorrow and much warmer temps late this week. 

As for convection, it looks better than today, with NAM showing a little CAPE and lifted index slightly below zero.  Our 00z RPM shows a nice area of lifted index 0 to -1 from PDX to OLM from 2-5pm.  CAPE goes up to around 500 j/Kg as well.  Could be a few hours of quite active weather tomorrow for sure.  Storms should come from a very steep northerly direction, moving SSE.  Hail is likely again and thunder seems slightly more likely than today.  There was ONE lonely lightning strike west of the Cascades today around 4pm.  That was a mile or so NW of Lacamas Lake in the far East Vancouver/Camas area.

We get quite a break as the low moves off to the east Thursday and the east Pacific goes real quiet…much more typical for this time of the year.  850mb temps rise to around +5 on Friday afternoon.  That plus either northerly or weak offshore flow could easily push temps up to 70+.  We’ll stick with 68 for now…but 70-72 is also possible if we do actually see easterly flow through the Gorge.  Seems like the upper-level flow doesn’t favor offshore flow down below from my experience though.

Mother’s Day weekend looks pretty nice now…Saturday should be a nice day like Friday, and then Sunday some showers may pop up, but the system approaching California appears to head mainly down to…well…California.  SIn fact the new 00z GFS has us mainly dry Sunday through early next week.  I’ll ignore the big ridge showing up on the GFS for later next week…for now.

Chief Meteorologist  Mark Nelsen