Some changes to the forecast today. After a week of showing a strong system dropping into the Sierra Mon-Tue the forecast models have pulled way back since yesterday showing a weak ridge to our South now and the heavy precip staying in Northern CA up to Oregon and Washington. The storms for Fri-Sat and Sat-Sun are still on track.

You can see the cut-off low spinning off the coast and that will slowly move towards the coast and finally come inland during the day on Friday. The snow levels will start around lake level and then could rise slightly above Friday night into Saturday. The amount of moisture with this won’t be a lot and right now it looks like we could see 3-6 inches above 7000 ft by Saturday morning with 6-9 inches along the crest. At lake level it will depend on snow levels.

A moist flow keeps the precip going Saturday into Saturday night with snow levels in the 6500-7000 ft level. That is all snow on most of the mountains with a mix for the base levels. Going into Sunday the cold front approaches and snow levels begin to come down. By Sunday morning we could see another few inches above 7000 ft and 3-6 inches along the crest. Lake level should begin to see snow accumulate again Sunday morning.

The cold front moves through on Sunday with snow levels below lake level and snow into Sunday night. By Monday morning we could see 3-6 inches at lake level and 6-9 inches above 7000 ft. That would bring 3 days storm totals to 6-9 inches at lake level with some of that washed out by rain, 12-18 inches above 7000 ft and up to 2 ft on the crest. I’m being conservative because of the model trends and the snow amounts will be lower compared to liquid amounts because of the lower snow:water ratios with the marginal snow levels. This will help to build bases.

There will still be a trough along the West Coast for Mon-Tue with a stream of heavy moisture into the West Coast, but it now looks like the heaviest moisture will stay just to our North. There is still not agreement among the forecast models on how much moisture does get in to the Tahoe Basin with the GFS cutting off precip completely and the European and Japanese models keeping light precip going. The snow levels however will start rising up to and eventually above 7000 ft by Tuesday, so it may be better just to cut of the precip altogether if the trough isn’t going to dig further down the coast.

Here is the GFS model for total precip through Tuesday. This is one of the drier model runs and shows around 1-1.5 inches for the Tahoe area.  You can see how much more moisture is aimed to our North and Norwest

Either way it still looks like we could see a brief break next Wednesday which is the busiest travel day of the year.  After that there is not much agreement in the forecast models with the GFS bringing a decent storm in on Thanksgiving into Friday and continuing to bring in storms through week 2 with a ridge North of Hawaii and low pressure off the Pacific NW coast.  The European has us on the Southern edge of a storm the weekend after Thanksgiving and then the opposite pattern week 2 with a trough North of Hawaii and a ridge over the West Coast.

Here is the GFS total liquid forecast for the next 2 weeks showing up to 7 inches of liquid.  If the GFS is right we could see twice as much precip week 2 as week 1.

Looking at the teleconnections we are still in a negative PNA pattern going forward which supports a West Coast trough.  The CFS v2 long-range climate model agrees with the GFS and continues to show wet conditions along the West coast over the next 4 weeks.  Here is the forecast week by week.

So it looks like there is a good chance the early season storms could continue into December.  The details just have to be ironed out we get to each week.  Stay tuned for updates to the details of snow amounts and snow levels for the storms this weekend….BA

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