Another Storm Recap:
We have some of the final numbers now from the impressive storms over the weekend.
A foot of rain near Alpine Meadows! The rest of the Tahoe basin saw 3-9 inches of rainfall. That helped to fill up the lake.
In the Saturday post I had forecast 2-3 feet of snow above 9000 feet. In the Monday post I was nervous about that prediction because I personally was not able to verify it. Luckily some people did go up there and ski it. Snowbrains.com posted an article yesterday which had a snow report by Travis Ganong in which he verified the 2-3 feet of snowfall up high.
Big Winter Ahead?
The question most are wondering is what does this mean for the upcoming Winter if anything? So I put together a graph this morning of the rainfall on Donner Summit every October since 1970 using the data from the Central Sierra Snow Lab.
You can see that we are currently running at the 3rd highest October behind 1982 and 2010. Those were also the 2 biggest snowfall seasons. There are 4 Octobers over 8 inches of rain, and 3 of those were above average Winters for snowfall. The only kink is that in 1975 we ended up with only 56% of average snowfall.
We still have 12 more days to go and we do have more storms in the forecast. We only need 2.36 inches of rain to be the wettest October. I'm not sure we get there but this is still a great start to the water year!
We have clear skies and warming temps through this weekend. Highs will be in the 60's with plenty of sun.
There is a trough digging down off the coast by Sunday. Right now that trough doesn't look as deep as a few days ago and it doesn't look like it will pull as much moisture as well. We could see some light rain and high elevation snow Monday into Monday night. Snow levels around 8000 feet.
GFS total precip forecast.
The latest European model run pushes up to a half inch of liquid near the crest. We will keep watching but for now only expecting some light rain showers.
The next chance of storms looks to be around the end of the month. The long-range models show a cut-off low off the coast that could pull in moisture before it moves inland around the end of the month. We will keep watching that as well.
The Winter Forecast:
I want to keep looking at the Winter Forecast this week. We can start today by just looking at the change in the forecast back to a weak La Nina.
Weak La Nina's historically are below average snowfall for Lake Tahoe. ENSO neutral Winters average below average snowfall as well, but that is from wild swings of very dry and very wet winters. What is interesting about weak La Nina winters is the consistency of the snowfall numbers without wild swings.
Here is a graph I made of the snowfall for weak La Nina seasons on Donner Summit at the Snow Lab.
You can see that most fall below average and all combined the average is 92% of average snowfall. But there are not any dry winters below 300 inches, and not any big winters above 500 inches. So while we hope for a big Winter, at least there is consistency historically to point us towards what we could see.
The two above average seasons happened in a cold PDO, and weak La Nina in a cold PDO jumps to 95% of average snowfall from 88% in a warm PDO. The PDO is still in the warm phase but has been cooling since Summer and was only at .45 degrees above average at the end of September. So we could be near neutral or even slightly cool this Winter.
I want to look at more variables this week. For now with a weak La Nina once again looking possible and the PDO cooling, I think history says my snowfall forecast should adjust from 85-92% of average this season to 88-95% of average snowfall.
Mt. Rose already has 6% of their season total...
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