Chilly, Then Hot

May 8, 2008

SnapshotI admit I’ve been a bit negligent lately.  I try to post something to this blog every day.  Lately the weather has been pretty slow too.

The constant onshore flow of marine air the last 2 days has really taken a toll on our high temps.  We’ve stayed in the mid-upper 50’s both days…only 56 today.  A slight upper-level ridge gives us warming throughout the atmosphere tomorrow and Saturday, which should help break up the marine layer.  As a result temps warm up to normal.  That’ll be nice.

Next weather maker is a cold front for late Saturday.  Quite a drop in the freezing level from around 10,000′ midday Saturday to under 4,000′ Sunday A.M.  Not a whole lot of moisture either with the front or behind it for Sunday.  Interesting how April and May have been chilly, but defiinitely on the dry side.  Looking at the 7-10 day maps, it sure looks to be mainly dry as well.

Speaking of 7-10 days:  Models are in some pretty good agreement on a strong ridge developing in the perfect location to give us unusually hot weather for mid May next Wednesday-Friday.  As you might expect, model solutions are varying day by day and run to run.  Some are way up in record territory for temps.  I see the 00z GFS again has 850mb temps up to beyond 20deg C and 592dm heights at 500mb.  The 00z GEM (Canadian) has gone nuts with a 596dm contour over southern Oregon next Friday.  If it was June, July, or August, that would give us 100 degree weather with offshore flow.  We’ve never been above 93 before May 22nd in Portland.  Twice in the last 7 years we’ve hit 95 in the 2nd half of May, both times 850mb temps at SLE were either 21 and 22 degrees at the peak of the heat.  This forecast ridge could produce those same temps.  One fly in the ointment is the 12z ECMWF.  It was significantly flatter with lower heights…we’ll see if it gets back on board at 00z or is a harbinger of flatter flow that the other models will follow.  Either way, get ready for a warmup!  Mark Nelsen