December arrived with record warm temperatures across the region. Wednesday (the 1st) was the warmest December day we’ve seen in Portland since 2015! These are just a few of the records set that day. Notice several spots in eastern OR/WA set all-time December high temperature records.
Cliff Mass (UW) in his blog called this the 2nd great Northwest heatwave of 2021. By that he means that many areas east of the Cascades observed “heat” just as anomalous as the June event; 25 degrees or more above average in spots.
We cooled off nicely today after a cold front passed through yesterday morning. Highs today were back in the 40s along the I-5 corridor…much more seasonal.
The mild/warm westerly flow in the upper atmosphere is changing to a setup where cool troughs dig down from the northwest, passing through our region. Each one should spin up some sort of wet system. So we can expect precipitation regularly over the next 7-10 days. Here’s the view Saturday
Then Monday; another trough passing by
Then a third next Wednesday
Looking farther ahead, to Monday the 13th, models GENERALLY have more troughing digging into the eastern Pacific.
In general this whole setup the next 7-10 days is cooler than normal. At this point I don’t see any surge of cold arctic air moving south, but it may be close at times. This chart shows things well. It’s the ECMWF 850mb temperature ensemble chart. It shows temperature (C) around the 4,000′ elevation for the next two weeks. Green line is the average of all 51 ensemble members. I’ve drawn the yellow highlight at 0 degrees.
Basically for pass elevation snow in the Cascades it needs to be at/below that yellow line. That’s the case most of the next two weeks…very good. Finally, we’re going to see a snow base develop in the mountains, and it’s not going anywhere this time.
It’s that time of year! The next 2.5 months are primetime for snowfall in the lower elevations of NW Oregon and SW Washington. I’ve got a few thoughts on that. The pattern I’ve shown above CAN bring snow to the lowest elevations of the region, but right now it doesn’t appear to be quite cold enough to do that. Sure, late next week 850mb temps dip to around -6 or even -7 at 850mb. That means foothill snowfall for sure (1,500′ or higher). But it takes more than that to get any sort of widespread snow event to the valley floors. I’m not saying we won’t see snowflakes at some point in the next 10 days, but nothing really sticks out on the maps right now. Note there is almost no support for significant snowfall from ECMWF ensemble members in the next 10 days. This is for Aurora/Canby; I chose a spot in the middle of the valley to avoid low resolution modeling issues. Ignore anything beyond 10 days…it’s a crapshoot after that.
- There’s no sign of a cold “arctic blast” the next 7-10 days. My exposed chicken coop waterline will remain on for now. Beyond that, the 15th and after? Who knows!
- I don’t see any sort of widespread snow/ice in the lowlands in the next 7-10 days. I haven’t put my snow tires on yet and don’t plan to for now. However, I would not be surprised to see flakes mixed in with rain at some point during that period. Or even a brief snow on the hilltops…maybe.
- It’s quite possible we see at least some partial ski area openings NEXT weekend, the 11th/12th
That’s it for now. Have a great weekend!