Mid-Winter Doldrums; Split Flow and Drier Than Normal

January 2, 2018

9pm Tuesday

We’ve entered a New Year but the old and relatively slow Pacific Northwest weather pattern continues.

Much of December we saw upper-level ridging either overhead or off the west coast of North America.  Now the first week of January we are in a “Split-Flow” pattern where systems stretch apart as the move toward the West Coast.   Notice you see it in the forecast for Thursday PM and again next Tuesday from the ECMWF model:

The net effect is the same we saw in December…drier than normal plus a mild pattern in the mountains and coastline.

The past two days it’s been mild/warm in the mountains but chilly in the valleys as an inversion sets up.  It was just as warm at Timberline as Troutdale today.

With splitty flow expect weak Pacific systems over the next week.  Note though that the ECMWF ensembles give us about average rainfall over the next 10 days.


Somewhere around 2″ in the Willamette Valley is pretty typical for a 10 day stretch in January.  What we DON’T see is a setup for low elevation snow/ice, flooding, or a windstorm.

We are about halfway through our “storm season” west of the Cascades, so there is PLENTY of time for things to turn around.  But it sure doesn’t seem like a La Nina winter so far does it?   In 2013-2014 big snow in the mountains and regular stormy/wet weather didn’t show up until February.  That wasn’t a La Nina winter, but close, a “cold neutral” year.  We’ll see what shows up the next few weeks.

In the short-term we have a raging east wind this evening in the Gorge.  Crown Point gusted to 92 mph today and Corbett up to 79.  Most winters that’s about the highest it gets in either location.  That strong wind will continue through Friday morning, then back off dramatically later Friday.  Today was notable since at least some of the wind made it deep into the metro area.  Notice the 30-40 mph gusts in the West Hills and down into northern Clackamas county too.

Wind Metro Peak Gusts East Wind

There is a decent chance we see freezing rain in the Columbia River Gorge either Thursday morning or Friday as moisture rides over the cold air coming through the Gorge.  It will be too “warm” for freezing rain just about everywhere else west of the Cascades.  The only possibility would be overnight cooling and clear skies followed by sprinkles at sunrise.  The GFS says that could happen Thursday AM, ECMWF says no.  We’ll keep an eye on it.

Chief Meteorologist Mark Nelsen