“Real” Summer May Be Less Than A Week Away!

June 29, 2012

We are just 3 weeks away from the warmest temperatures of the year (the average):

From July 19th to August 13th the average high temp in Portland is 82 degrees.  After that it starts to fall off again.

Today’s high of 77 was perfectly normal, although the warm temperature along with almost totally cloudy skies was a bit strange.  We’ve got another warm night on the way too; last night it only dropped to 62 here in Portland and tonight should be similar.

Tomorrow the cold front offshore right now moves inland over us.  There is plenty of moisture to work with…precipitable water was 1.17″ on the Salem sounding this evening.  That’s much higher than normal.  Lifted Index goes below zero tomorrow afternoon with even some decent CAPE west of the Cascades too.  So the chance for convection is pretty good, but there doesn’t appear to be a big trigger for widespread thunderstorms.  It’ll be interesting to see if we do get some decent downpours.  Our RPM shows a few heavy showers/t’storms midday and into the afternoon.

After tomorrow, Sunday and Monday look quite nice, just leftover clouds through a good part of Sunday.

A bit of a change the past 48 hours; models are saying that our “real” summer will be here in about a week.  Look at the 12z ECMWF ensemble 850mb temp chart:

Notice the operational (blue) ECMWF goes above average (green line) on the 5th of July, the ensemble mean (red) slightly later.  What really adds credibility to a major change on the way?  Almost every single ensemble member (there are 51) is above average after next Friday.  And we’ve seen several runs like this now.  The ECMWF would imply 90 degree temperatures are likely by next weekend.

The 00z GFS is keeping the warm weather theme going as well.  Same story with the ensemble average going above normal next Friday (the 6th).  Notice this model too has 850mb temps up in the +15 to +20 degree range by next weekend.  Next weekend may be very summery!

This does occasionally happen; if you’ve lived here long you know that sometimes summer arrives like a “switch has suddenly been turned on”.  And this would be the time of the year for that to happen.

OR, just like in winter, models may be having trouble with the persistent pattern of cool troughs close by and will revert back to that pattern in the next 48 hours…we’ll see.

Chief Meteorologist Mark Nelsen