Tahoe Daily Snow

What Does a Dry October Mean for the Season Historically?

Summary

High pressure is building in over the West Coast bringing us a prolonged period of dry weather. The good news is that, at least for now, the skies are clear of smoke. Hopefully, we will see a change in the pattern by the end of the month.

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Short Term Forecast

We saw a dry cold front move through the area over the weekend. That brought some clouds, gusty winds, and slightly cooler temperatures. The best part is that it cleared most of the smoke out of northern CA! (OpenSummit.com)

smoke

Unless more fires start or expand, we should see clearer skies continue this week except for farther south down near Mammoth. 

High pressure will continue to build in over the West Coast through the week with sunny skies continuing.

ridge

As the ridge shifts north we may see a northeasterly flow for the 2nd half of the week. That should help to keep the skies clear of smoke. Highs in the 70s at lake level and 50s for the upper elevations. (OpenSummit.com)

upper elevations

The 10-day precipitation forecasts have the storm deflection dome over CA...

precip forecast

...and the 10-day mountain forecasts are very boring for now.

snow forecasts

This is frustrating if you were hoping for an early start to the storms this season, especially after a late start last season and an early end to the season due to the virus. I'm with you...

Luckily we are super busy here at OpenSnow building out lots of new All-Access features, including lots of new forecast maps, for the upcoming season! Consider joining us and letting us work directly for you to try and build you the best snow forecasting site on earth!

Extended Forecast

The long-range models show storm activity picking back up into the Pacific NW the last week of the month. We are still being shown on the southern edge with only light precip if any. We will keep a close eye on it and let you know as soon as a storm is on the horizon.

Some have asked about what a dry October could mean for the upcoming winter season. It is still VERY early with October being only the 1st month of the new water year. We are only 11 days into October. I usually don't even start to analog with dry seasons until we see both a dry October and November. The models can change fast and we could still see storms before the end of the month.

Assuming we don't see more than just some light precipitation thru the end of the month, we could play around with some history. We average around 3.7 inches of total precipitation at the Snow Lab near Donner Summit in October. Below are the 7 Octobers since 1970 that we had less than 1 inch of precipitation (less than 20% of average), and the totals for the entire season through May for total precipitation and snowfall as a % of average those seasons.

graph

You can see that 4 of 7 seasons with a dry October ended up above average for precipitation and snowfall. So there really isn't any correlation between a dry October and the rest of the season. Here is a look at a graph of the 10 Octobers that saw "0" of snow and what they saw for snowfall the rest of the season. The snow doesn't really start falling in earnest most seasons until December.

dry starts

Here is how those seasons broke out by month, with most of the snow falling Dec - Feb. 

snow by month

What's interesting is that the seasons that start late tend to end earlier. March on average across all seasons tends to see snowfall closer to that of February.

by month

As we head towards the Winter season we continue to watch the sea surface temperatures. There is a lot of cold water along the equator, consistent with moderate La Nina conditions.

ssts

NOAA has a forecast now for a moderate La Nina this season, with some models peaking near a strong La Nina around January. That favors a wetter Pacific NW into northern CA historically, with below-average precipitation south of Tahoe.

mod la nina

That is similar to what the European model is forecasting for this upcoming winter season.

euro la nina

So don't fret, there is still a whole winter season ahead, even if we have a dry October. Of course, there are a lot of other teleconnections and patterns that could affect the storm track this winter. Some of that tied to the SSTs over the rest of the ocean north of the equator. Some of them are short-term patterns that can only be forecast out a week or two. that is why seasonal forecasts are so unreliable.

We will continue to watch the patterns develop as we head through the fall. I'll post another outlook on what I think could happen this winter around the end of October. In the meantime, lots of work to do on new powder tracking features! I may have another surprise for you as well.

Stay tuned...BA

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