Just 10 Days Away!

February 7, 2011

The title is a bit of an inside joke on the weather blog.  For a good chunk of the last 4 weeks we’ve seen maps show a possible change to much colder and/or snowy weather, maybe even in the lowlands.  But it’s always just beyond the range of our 7 Day forecast…usually out around the 240 hour forecast period (10 days).  So once again today, the chance for snow down below 2,000′ appears to be about 8-9 days out.  Even then there is not a good setup to get snow down to the Valley floor.    This is one of the big reasons we don’t forecast more than 7 days ahead of time.

Models do all show a major change in the western ridge, eastern trough pattern that’s been the theme for the past month.  A trough is going to set up near the West Coast, allowing quite a bit more rain and mountain snow into our lives.  Details are a bit up in the air, but in general it’s a cooler and wetter pattern.

So are we done with the chance for snow this season at the lowest elevations? 

No, but the chance of getting a significant snow or snow/ice storm is fading quickly, especially since models show nothing of the sort through at least February 16th.  And “real winter” in the Pacific Northwest lowlands west of the Cascades is mid-November to mid-February.  By “real winter”, I mean the chance for a big arctic air outbreak or prolonged snow/ice event.  Sure, we can get several inches of wet snowfall after that time, but a quick examination of record low maximum temperatures at PDX shows a quick change right after Valentines Day.  After that time is EXTREMELY rare to see a high temperature below 35 degrees.  In fact there are no sub-freezing high temps at PDX after February 16th, except for one day in early March 1965.

Chief Meteorologist Mark Nelsen