Cool & Dry November Weather On The Way

November 5, 2012

Highlights This Evening

  • One more warm day tomorrow with temps well into the 60s
  • Enjoy it, I don’t see any more of the warm stuff on the way; last mid 60s until February?
  • Much cooler the rest of the week and into the weekend
  • Not much rain between now and Sunday!
  • First Frost is possible even in urban areas Friday or Saturday morning.

I was sick the last half of last week, plus the weather has been dead, so not much to talk about anyway.  But finally some interesting weather coming up over the next 7-10 days…hopefully.

5 out of the last 9 days we’ve tied or broken record warm low temps.  We won’t today since we’re already down to 54 at 9pm and it’ll be lower before midnight.  That’s a long stretch of warm nights!  Yesterday Salem and Eugene were into the 70s for record highs too.  It’s been nice to be outside with no jacket in November, but now it’s going to cool off.

The Big Picture
It appears a longwave upper-level ridge is going to be taking up residence out around 160W  off/on the next 10 days or so, which means a trough located most of the time along or off the West Coast.  There is amazing model agreement on this general plan in fact through the 10-14 day period.  Here are the 500mb height anomaly (all ensembles) maps from the 00z GFS, 12z GEM, & 12z ECMWF for 10 days from now: 

They all look pretty much the same don’t they?

Here’s the brand new 00z GFS model 850mb ensemble chart, very good agreement on below average 850mb temps through the next 9 days:

This means cooler than average weather returns.  We are just about into the time of year (mid November through early March) when “cooler than average” means real chilly.  So it’s going to be quite a change the next few days going from well above normal temps to a few degrees below normal.  And it goes without saying that after about November 15th, we watch very closely to see if that perfect snow or cold pattern will show up.  You usually want the ridge a little bit closer for an “arctic outbreak”, but with the ridge a little farther away, it can be a great snow pattern for the foothills and Cascades.  Right now nothing looks too interesting on the maps for the next week.  We have a first cold upper trough moving down over us Wednesday-Saturday.  We don’t get dry offshore flow, but even so it might be a cold enough atmosphere (-5 deg @850mb) that we get clearing and finally get a frost in the city (or at my house, I still haven’t been below 36…cheated…).  With an upper-level trough digging so sharply over us Wednesday and Thursday, the main precip action is farther south.  In fact the rain we have in the forecast for Thursday may never make it into NW Oregon east of the Coast Range as that system heads into California.

What about skiing? 
Very little moisture means little/no snow through Saturday, so no skiing for this 2nd weekend in November.  But with a cold trough over us next week, a couple wet storms could get some areas open for the weekend before Thanksgiving?  Think positive, but I definitely don’t see an early start to the ski season though this year (well before Thanksgiving).

Lower Elevation Snow?
This is the general pattern in which we would expect to see snow at least down to 2,000′, in fact I thought that would happen Thursday/Friday, but now just about all the moisture is farther south.   As of this evening, I don’t see anything on the maps through the next 7-8 days which would bring snow any lower than that.

Here’s what is NOT in the plan for the next 7-10 days:

  • Warm and Wet weather (we had enough of that for 3 weeks)
  • A Windstorm Pattern

Chief Meteorologist Mark Nelsen