The first half of December has been one of the driest on Record for Seattle and Portland as well as Reno. In the Sierra if it doesn’t snow by the end of the month it will be one of the least snowy December’s on Record. The Pacific NW is normally the area that gets above average precip in a La Nina and the Southwest below average, but Taos, NM is having one of the wettest and snowiest starts to December on record.

This is really going to hurt a lot of the local ski areas as the Holidays approach and there is not much snow to ski on. The resorts with the most open terrain are those that have large snowmaking systems, but even those have limited terrain. This story is the same across the country as the storms have been staying up into Alaska and Canada, except for the Southwest where waves from the cold troughs have been cutting off and then tapping the subtropical jetstream.

Resorts in the Northeast are in about the same shape as they are in Tahoe with the storms all cutting up to the Great Lakes and bringing them rain. Kansas has gotten more snow than most of the mountain areas. The Rockies are doing ok thanks to the big snows still on the ground from November. So as you can see the giant high pressure anchored off the coast has really affected the entire country by blocking storms from hitting the West Coast and keeping the trough over the Central part of the CONUS (Continental United States).

I know that everyone is dying for snow and especially myself. It gets really hard to write about any possible signs of a pattern change for weeks instead of the details of a big storm that is going to hit. Even a little storm would be nice. I had forecasted a late start to this Winter and a dry December back in November, but even a dry December usually means at least some snow.

I had a comment from a reader that I should just say it’s not going to snow and not get everyone’s hopes up for a long-range pattern change. I can do that. There is a really good chance that we don’t see any snow for another two weeks, maybe 3. For the past 2 weeks I have only talked about any signs for a pattern change in the long-range and have not said much about the short-range because there has been nothing significant in the forecast for the past couple of weeks, and the next couple.

Being that this site is a snowcasting and not a weather forecasting site I only focus on big snowfall events, and therefore I try to stay optimistic and keep letting you know about any positive signs I see in the long-range. There haven’t been very many this month. The AO has been positive and we want negative, the PNA has been positive and we want negative, and the MJO died before entering the Western Pacific.

The differences between this time last year and this year is the AO was negative, the PNA was negative, and the warm pool of water in the Western Pacific was not extended quite as far to the North of Hawaii. That alone may be what has helped to keep the jetstream coming off of Eastern Asia a little stronger and further extended East which would help to pump the ridge in the Eastern Pacific.

The first day of Winter is on Thursday, the La Nina has been strengthening, and the PDO is negative. That all tells me that the PNA can’t stay positive forever and it will go back to its usual La Nina negative state as we go into the Winter. That will bring the trough back down the West Coast and the storm track into the Pacific NW. On top of that the AO should also go negative if the stratospheric warming continues over Siberia pushing North and East.

Be careful what you wish for in the Pacific NW because as we head into January it should be game over in Alaska and the Southwest and game on in the Pacific NW. The cold could be as impressive as the snowfall. Don’t pay attention to the AO forecast at the top of the site, it is too early for it to catch onto the rising heights over the Arctic from the stratospheric warming. The storm train is already showing up on the models starting next week in Washington and then starting to push South.

Here in Tahoe we will need the jet stream to push further South down the coast. One way is for the ridge to retrograde allowing the trough to dig off the coast, but that is not showing up yet because of the positive PNA keeping the ridge off the coast. The other way is for the jet stream to be pushed South by blocking setting up to the North and an Arctic plunge down the coast crushing the ridge. The stratospheric warming and probable flip of the AO to negative would be something to watch for if this is going to really get good.

The latter scenario is being seen on the forecast models as about 50% of the ensembles and 50% of the operational runs are showing the jetstream crashing into Tahoe around or just after the New Year. Remember from the last post that we can see signs in the long-range that would point towards the flip and now we just have to wait for more model runs to catch onto the pattern change. Let’s Look at some of the model runs in the past 24 hours.

Here is the 18z GFS jetstream forecast for the 2nd of January.

You remember the Jan. 1st forecast from the GFS two days ago from the last post that first caught onto a New Year’s storm.  Here is last night’s 0z GFS.

And here is today’s 12z GFS…

And here is the 8-16 day precip forecast through Jan. 3rd from a mix of several models including those not showing a big storm yet.

50% of the models verifying a theory more than 2 weeks out is not a bad start.  We can never trust the models this far out on any specific storm, just look to see if they are recognizing a pattern change and they are.  It may take a little longer to change but we are heading in the right direction.

I know I’m getting your hopes up again, but after two more weeks of no snow you may be more depressed.  There is another trough dropping down to our East on Thursday bringing another shot of cold with it.  Then the ridge is going to shift closer to the coast next weekend and then inland which could bring some milder weather next week.  Meanwhile we will continue to watch for more signs of the pattern change.

I really hope we get another January 08 where by the end of the month this dry spell will be a distant memory, and we will be talking about the big snowfall.  Stay tuned……BA

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