Things are still looking good for a pattern change next week and we will start it off with the chance of some light snow with a cold trough this weekend. Things started off pretty good in November and you can see below there is still a lot of snowcover in the Northern Cascades and into Idaho and Montana. That snow is getting kind of stale though as we have had a break from big storms over the past 2 weeks.
The ridge of high pressure has been anchored off the coast all week keeping the storms to the North. The pattern is going to become more progressive starting this weekend with the ridge moving to our East and a new ridge forming further out in the Pacific near 160w. That will briefly open the storm door and then the ridge will move East again by Monday. That won’t stay though as we see the ridge reform further West in the Pacific again on Tuesday briefly opening the storm door before the ridge shifts back off the coast again.
The cold trough that drops down the coast this weekend looks like it will bring very light amounts of snow to the Cascades as the cold front pushes through on Sunday. The next storm will dive in from the Northeast Pacific on Tuesday into Wednesday. This storm looks like it will have a little more moisture and could bring several inches of snow to the Pacific NW including Idaho and Montana. Below you can see the jetstream pattern the middle of next week has the flow going into the Pacific NW.
This pattern should continue going into the weekend of the 17th with the ridge possibly flatting when it’s off the West Coast and continuing periods of retrogression back Westward in the Pacific. This should put the Pacific NW back into a more typical La Nina pattern for this time of year with a storm arriving every couple of days. Right now the forecast models are showing the possibility of some stronger storms the weekend of the 17th and going into the week before Christmas. Here is a look at last night’s GFS forecast for Wednesday the 21st showing a decent sized storm.
The La Nina conditions strengthened last week with all 4 regions cooling with 3 of them now below -1 into moderate La Nina territory. This would lead me to believe that the -PNA has to eventually come back and bring more permanent troughing to the West Coast as we head into the Winter. As we go into the Winter the Pacific NW looks to be in great shape for lots of snow. Here is the updated snowcover map through next Thursday and you can see that the snowcover has expanded from the smaller storm next week. Hopefully this map has a lot more orange and red by the end of the month.
Next week we will look more closely at the potential snowfall amounts as the storms get closer. BA