The last time we had a decent snowfall in Tahoe was on November 20th. The past three weeks have been very dry although cold. We are easily on track to the driest start to the Winter in over a decade. With the weak La Nina in the Fall going towards a possible moderate La Nina in the Winter and a cold PDO the thinking was that there would be a slow start to the snowfall, but this is getting to be a bit too slow.
We have been stuck in the same pattern of storms being deflected up into the Alaska and Western Canada by the ridge in the Eastern Pacific. Shots of cold have been coming down from Canada with lows spinning up as the energy interacts with the Southern stream across the Southwest. That has led to several cut-off lows that have brought snow to Southern CA, Arizona, and New Mexico. There is a similar storm bringing snow currently to the Southern CA mountains.
There will be another shot of cold air on Thursday as the next weak storm comes onshore into the Pacific NW and takes a dry path over land and to the Northeast of Tahoe. Over the weekend the forecast models were taking this storm a little further West down through the Sierra with a little light snowfall, but now they keep most of the precip away. Why change our luck now?
The teleconnection patterns are fairly neutral and there are no blocks forming that will change the weather pattern dramatically in the near term. The forecast models are all over the place next week which can be a good sign because it can mean a large scale pattern change is underway and they are trying to figure out how to handle it. Right now it looks like the pattern could become more active in the Pacific NW next week but not quite yet down to Tahoe. If the ridge pulls back a little from the East Pacific we could see a storm sneak in the middle of next week.
The pattern over the past few weeks has had a trough near the Aleutian Islands and a ridge in the Eastern Pacific. A pattern that we saw a couple of time last season that was responsible for some big snow weeks was a ridge near the Aleutian Islands and a trough stuck in the Eastern Pacific. The latest European actually hints at a ridge trying to build in where the trough has been near the Aleutians right after Christmas. Notice the circular dry area. That could be postive sign, we’ll have to keep watching.
The East Asian jetstream extending into the Western Pacific has been strong over the past month which has helped to pump the ridge in the East Pacific. That should weaken and retract as we head into the Winter especially with the La Nina. It should only be a matter of time before the trough returns to the West with cold and snow. The pattern should continue to become more active and snowy as we head later into the month. We saw a big comeback of Winter in January during the last moderate La Nina during the 07/08 season.
Lots of people have started to give up on Winter but Winter does not even begin until 10 days from now. BA