Lake Tahoe has been the victim of a large area of high pressure off the coast that has been deflecting storms up into Alaska and Northern Canada. Part of the reason is that the PNA (Pacific North American) teleconnection has been in its positive state. It is now returning more towards neutral and over the next couple of weeks we will slowly see a return of snow to the West Coast.
This week the ridge will still persist out around 140w in the Pacific keeping the jetstream well to the North in the Pacific towards Alaska and Northern Canada. Look at this image of the jetstream for this week.
This pattern has been allowing cold air to dive South out of Canada into the Western U.S. including Tahoe. There will be another shot of cold air today as another cold trough moves through. In this pattern however the cold fronts are dry and you won’t see much more than some light snow down the Rockies.
As we move further into the month and closer to Winter the jetstream will continue to strengthen and the ridge should begin to weaken and retrograde back in the Pacific towards 150-160w. That would allow the cold troughs and the jestream to dig down off the West coast and bring the return of snow. It looks like we will begin to see the pattern breaking down and shifting towards this by the end of the week.
The forecast models show the high pressure ridge in the Pacific briefly shifting West on Friday allowing the next cold trough to come down from Canada further West towards the coast. The ridge quickly shifts back into the Northeast Pacfic which could pinch the storm coming down the coast next weekend off from the jetstream forming a cut-off low. We have seen a bunch of these already this Fall and the hard thing is to forecast their path. Right now it looks like we could see this happen a couple of times next week so the chance for the storms to come close enough to Tahoe for some light snow events are there.
What we really need are some big storms though. As we move move closer to mid-month we should see the ridge in the Pacific weaken and we should have more of a zonal flow of the jetstream across the Pacific. Here is a forecast model of the jetstream for the beginning of next week.
Right now it looks like Pacific NW will begin to see the return of bigger storms towards the end of next week. We could begin to see bits and pieces of light snow from the Southern edge of those storms in Tahoe. As we progress further into the month the jetstream should shift further down the coast at times bringing a return of snow. Here is a forecast map for Friday the 16th showing the storms beginning to hit the Pacfic NW.
As we go further into the month the ridge should continue to weaken as the jetstream strengthens, and it should begin to shift Westward more permanently as we head into the La Nina Winter. You can’t trust the forecast models out that far but here is what the GFS forecast model is showing for the 21st of December right before the Holidays.
Although the forecast models will change a lot in the long-range you look for an overall pattern. Right now they are looking promising for an overal pattern change back to stormy right before Christmas. Let’s keep our fingers crossed. The Winter is still predicted to be a decent one. Not as huge as last year but even an average Winter is a big Winter in Tahoe. My forecast is for 105% of average snowfall in Tahoe this Winter, and if you missed my Friday post, here is the Accuweather.com updated Winter forecast that came out this week.
I will continue to watch all the patterns to see if we can get the snow back before the Holidays and the closer we get the better chances should get as we head into the La Nina Winter. BA