On to Warmer Weather

May 21, 2007

SnapshotAfter a wet two days (for May at least), it’s back to our drier May weather.  Looks like "storm" totals were anywhere from .25" westside of the metro area to almost 2" on the west slopes of the Cascades.  How’s that for orographic flow?  The weather pattern will be quite stable and, to be honest, a bit slow the next 7 days.  Onshore flow eases the next two days as the atmosphere itself warms.
Okay, I admit I did find something interesting that changes the forecast a bit for Friday.  A cold shot of air drops down into the Northern Plains later Thursday, which is accompanied by an area of high pressure too.  Both the 00z NAM & GFS show a sudden drop in dewpoints here in Portland by Friday morning along with an easterly wind, especially at 850mb.  So a brief, but strong offshore flow setup for us.  That along with 850mb. temps by Friday afternoon in the +12 to +14 range could easily push us into the 82-87 degree range.  ECMWF agrees, so that’s why our 7 Day forecast is significantly warmer than any other one in town.
Beyond Friday, as we head into the Memorial Day weekend onshore flow gradually increases.  So those of us that have camping plans early (me) will find the warmest temps the first half of the weekend.  But the big story in the Northwest of course will be the DRY weather for the weekend.  Locals know that Memorial Day weekend can easily be wet and chilly…Mark