Dry Two Days Ahead, Then Cool & Wet

October 16, 2012

Not much to talk about for Wednesday and Thursday as high pressure settles overhead.  The atmosphere does warm dramatically tomorrow afternoon through Thursday.  In fact by Thursday afternoon we’ll see 850mb temps up around +13 or so.  That plus a light south wind ahead of an approaching cold front means we might hit 70 once again…quite possibly the last 70 degree day of the season.

More interesting developments for later Friday and beyond.  For several days now models have been showing a cold upper level trough settling in along the West Coast, or just offshore, this weekend and possibly beyond.  Details are always an issue, for example will an organized system spin up or not within the cold air.  So I broadbrushed the Saturday-Tuesday forecast showing “Cold Showers”.

850mb temps will be a bit cooler than what we had today, so it’s quite likely we’ll see a dusting of snow in the Passes at times starting Saturday.  I could see several inches of snow at those elevations IF we get some more organized shower action.

Obviously it’ll be significantly cooler this weekend.  High temps only in the 50s.  IF we were to get a day with lots of showers and few breaks in the cloud cover, we might only hit 50.

The 2nd half of October does look cooler than average.  Take a look at the 850mb ensemble charts from the 12z ECMWF:

And the 12z GFS:

By the way, when we have a deep upper trough centered just offshore (as models show for Sunday and beyond), it isn’t a good setup for either heavy rain or high winds.  Too much energy moves down into the base of the trough and heavier moisture generally ends up in California.  Even if a surface low pressure center moves up the coastline, we don’t tend to get good pressure rises to the south for strong wind.

Chief Meteorologist Mark Nelsen