“…And,what happened if you watched the mountains in December, it was the lowest snow pack in decades. Ski resorts were unable to open for Christmas or even New Year. People were calling it…this winter was over. And then the weather did DUMPS – they call ‘em dumps. Big massive dumps of snow in Washington and Oregon, and all over.”

 

Ugh…it’s one of those nail-biting weekends in Northwest weather where we don’t know exactly what is going to happen, just 4 days from now. Either arctic air invades the region beginning Thursday or it doesn’t, depending on which map you look at. This model disagreement is notorious in the lead-up to cold waves (and cold busts). I could research and write an entire 2,000-word article on the phenomenon, digging into this perennial frustration in PNW winter forecasting. Maybe someday…

For now though, let’s focus on what we do know: Massive dumps of snow have fallen in the Cascade Mountains over the past 48-ish hours, and feet more are expected as we move through the coming week.

SKI SEASON IS HERE

This weekend was a long-awaited one for ski resorts: we finally have enough snow to get most operations into gear! All the lifts are open at Timberline Lodge, and four lifts at Mt. Hood Meadows. Since Friday Timberline has seen 29” new snow at its lodge, while Meadows got 26”. Unfortunately there are no big “touristy” holidays in January-March, just MLK and Presidents’ Day. So it’s pretty hard to make up losses from a really bad Christmas season.

These snow dumps are the result of a cool upper-level trough over the Pacific Northwest, which allows colder systems to slide in from the North Pacific. Showers also tend to move in nearly perpendicular to the Cascade crest, which maximizes orographic forcing of additional precip on the slopes. Yesterday afternoon some snow was reported as low as 1,000 feet elevation in the Cascade foothills.

The next strong system sweeps in Monday evening and Tuesday morning, bringing even heavier snow in the Cascades and gusty SW winds in the western valleys. The National Weather Service has a Blizzard Warning for 3,000 feet and up in the Cascades Tuesday/Wednesday, and a Wind Advisory for the valleys.

How much more snow? The 12z GFS maps show at least 4 additional feet for the highest slopes by Thursday morning…or 5-6 feet if we assume a fluffy “Kuchera” powder. Needless to say, travel over the passes will be next to impossible, for at least 48 hours beginning Monday night.

So by Thursday morning, the Cascades will have truly massive dumps of powder at all the resources. That brings us to the next question, for Thursday…

ARCTIC AIR MESS

The last 5 days or so have been a crazy ride on model maps, ranging from no lowland cold at all to truly historic cold. I’m not going into detail here, but I will post a couple images to show you how horrible it has been. First, last night’s 00z ECMWF, for next Sunday at 4am. Bitter arctic air comes in Thursday night and is fully entrenched by Sunday morning, with 850mb temps of -15c for Portland and -22c for The Dalles:

But the 00z GFS pushed all the cold air east instead on Thursday/Friday, and we’re in seasonably cool onshore flow Sunday instead, with a -3c airmass:

The Canadian GEM model has been quite similar to the ECMWF, putting a lot of cold air into our region. Interestingly, it’s the GFS that has been most tame this time- usually, it’s the most outlandish of the models in these kinds of “wishcasting” events.

Very soon the cold air will be on the move, so there’s not much time left for large-scale uncertainty. Either the GFS turns colder or the other models will suddenly back off. Or they both meet somewhere in the messy middle.

MONDAY AM UPDATE: The overnight model runs have begun to converge, and the solution looks especially ugly. We appear to have a shallow intrusion of cold air into the Puget Sound, Columbia Basin and Gorge. This is terrible news for Portland, because it means an ice storm could be on the way! Check out the 00z Euro map (GFS is similar but not quite as cold):

We just had an ice storm last winter…and a crippling ice storm two winters before that. Frankly, I’m almost wishing the cold air stays away entirely if this is the case. Nobody enjoys power outages and being stuck at home for 2-3 days. We shall see.

 

Karl