Warmest Day Of December & Low Mountain Snowpack

December 29, 2017

7pm Friday

What a warm day!  Temperatures reached well into the 50s west of the Cascades with even some lower 60s showing up south of Eugene.  Central Oregon got into the warm weather act with low 60s in Redmond and Bend.

Todays Observed Highs OrWa 2017

Today we have been in the warm sector between a warm front that passed overhead last night and an approaching cold front.  The gusty southerly wind brought in the warm air.  The wind has remained light easterly in the Gorge, keeping temperatures in the 30s there.  This warming winter wind after a cold spell actually does have a name; although it’s rarely used anymore.  It’s the original “Chinook Wind” before that name was more commonly used to refer to westerly warming wind off the east slopes of the Rockies.  We should use it more often just to annoy those folks in Denver.

At 7pm the cold front is moving into the western valleys of Oregon and Washington, evidenced by falling dewpoints and temperatures at Astoria.  A surface low pressure area is moving across NW Washington and will move into Eastern Washington the next few hours.  This reverses the pressure difference across the Cascades, leading to a gusty WEST wind through the Gorge.  The WRF-GFS forecasts 4-6 millibars by 10pm!  That means you’ll make a quick jump to 50-55 degrees in The Dalles sometime between 9-11pm.

Unfortunately for the mountains and ski areas, it has been pouring all day long.  The snow base dropped by about 10 inches at Timberline due to the warm rain.   Radar and models show this is not the type of system where we get lots of cold showers behind the front tonight.  In fact we only expect a dusting to 3″ at the ski areas by midday tomorrow.  The fresh snow just before and during Christmas was great; salvaging what could have been a really rough Christmas Break.  But all signs point to a continuing pattern of weak and warmer than normal systems for the next 7-10 days.  Take a look at the latest snowpack numbers…only about 50% of normal for the end of December:

Snowpack Oregon Plus Facts

Snowpack Oregon Plus Facts2

We’ve seen this in the past, but generally not in La Nina winters.  I’m not sure what’s going on this year since we keep seeing ridging popping up over or just west/northwest of us.  You may also notice the lack of stormy weather.  How often (since October) have we seen this gusty south wind and a strong frontal system?  Not much…this winter is reminding me of the La Nina of 2000-2001 which turned into quite a dud for the region.  That year we had one ice event in mid-December too which brought freezing rain to the metro area.  Other than that it was a mainly quiet winter.  We’ll see, there’s still a good 6 weeks in which we could get a widespread snow/ice event in the lowlands and of course we can get a wet morning snowfall all the way into March.  And this weekend should be just fine with much colder temps firming up the snowpack tonight

Snow Report

In the short-term, we have a nice weekend ahead with mainly dry weather.  Sunday and Monday we’re back into the chilly east wind pattern.  Your New Year’s Eve will be chilly and breezy (or very windy if you live in east metro) but dry and comfortably cool

New Years Eve Fcst

Chief Meteorologist Mark Nelsen