A Cold and Dry December

December 26, 2013

It’s pretty obvious that we won’t get much rain in the next 5 days.  A few showers are possible tomorrow afternoon and/or Monday/Tuesday.  But that’s it.  As of now, we’re running in 2nd place for December precipitation here in Portland.  1976-’77 was drier.  A chilly month too!  As of now it’s the coldest month in 4 years (Dec 2009 was slightly colder), and those two are the coldest since 1990.  I was surprised some other months in the past 10-15 years haven’t been colder, but all those other years we saw a warmer spell at some point during the month.  This year it was the arctic blast, then lots of inversion weather with very few days at/above 50 degrees to balance out the temps.MarkRain_DecemberFactsToday was a classic winter inversion day in our region…50s and 60s in the mountains  and mainly 30s in the western valleys under the fog and clouds.


The weak system tomorrow probably won’t do much to change our weather.  Without significant offshore flow (easterly Gorge wind), it’s tough to keep the fog and low clouds away here in the metro area.  Still, we had just enough easterly drift (overhead, not at the surface) to clear out most of Multnomah County for a 2nd day.  Here’s a sat pic at 1pm:


Notice everyone else below 1,000′ or so is stuck in the muck between the Coast and Cascade Ranges.

Long range maps don’t show any dramatic changes to our weather through at least 10 days.  The GFS has hinted (for all of 2 runs) the ridge might try to push farther offshore, possibly setting us up for colder weather and/or better chance for mountain snow.  But it also did that about two weeks ago, showing a cold and wintry pattern between Christmas and New Year’s.  We see now how that turned out…

So please continue to enjoy the fog, sun, and even a few sprinkles!

Chief Meteorologist Mark Nelsen


ECMWF Weekly Maps: Ridging Continues?

December 26, 2013

Twice a week the ECMWF is run out to one month and we see an average of the 500mb heights for the week from all the ensemble members.  I just looked at last night’s run.  Of course you can never read too much into these maps, but sometimes they give us a general idea of what might be ahead.  In this case it appears some sort of higher than normal heights (ridging) wants to stick around through at least mid January.  We’ll see.