Tahoe Daily Snow

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By Bryan Allegretto, Forecaster Posted 5 years ago December 11, 2018

The Trend is Your Friend (or Not)...

Summary

- We have a break Tuesday-Thursday as the next storm moves through to our north. We should warm up again into the 40's at lake level and 30's in the upper elevations. Watch for upper mountain wind to gust to 40 mph on Wednesday. - The next storm for Friday is falling apart as it moves in. We should see some clouds and gusty winds, and maybe a few snow showers. But not expecting measurable snowfall. - After a break on Saturday, another storm for Sunday night is starting to show signs of splitting as well, but right now it looks like it could hold together enough for several inches of snow. The trend is towards drier so we are hoping this storm can at least bring some measurable snowfall. - In the long-range, it looks like a drier pattern sets up the week of the 17th. No signs of a significant storm of not over the next 2 weeks...

Short Term Forecast

Sorry for the late post, having internet issues all morning...

We have some clouds around this morning from a weak system that moved through Monday.  The Monday system performed as expected bringing through a few light snow showers and no accumulations.

We have a storm moving through to our North for Wednesday and another storm falling apart Friday.  We have been in this pattern where storms are weakening and splitting apart as they move into CA, and that will continue through the weekend.

Looking at the satellite you can see the pattern is very active with storms continuing to move into the West Coast.

satellite

Unfortunately, we are in a pattern where the storms are falling apart by the time they reach Tahoe.  We were hoping that the weekend storms would have a better chance of pushing in and holding together, but the trend continues to be towards them weakening as well.

The Canadian model was the one hold out for the Friday system, showing up to several inches of snow possible.  It has now not only gone the way of the other models, but is now one of the driest.

Canadian

The model average is less than a tenth of an inch of liquid.  So I have removed any snowfall from the forecast.  Only expecting some gusty winds and a few light snow showers possible just like the Monday system.  

So right now we should remain fairly dry through Saturday.  Expecting clouds and wind Wednesday and Friday but no more than a dusting of snow.  Temperatures remain in the 30's on the upper mountains and low 40's near lake level.

Sunday Storm:

For the Sunday storm that is trending towards weakening and falling apart as well as it moves in.  We now have forecast models like the GFS and Canadian models showing less than a quarter inch of liquid on the high end. 

The European model is the wettest, but it is really digging the trough deep down the coast and tilting the orientation counter clockwise, known as a negative tilt.  This turns the flow from the south or even southeast which is horizontal to the Sierra instead of perpendicular.  You want a perpendicular flow to push the moisture over the crest into the Tahoe basin.  Storms that do this can drop a lot of precip on the west slope and push nothing into the Tahoe basin like some of the models are showing.

Here is a look at the large trough associated with the strong storm approaching the coast Sunday.

strong 

6 hours later...

medium

12 hours later...

weak

So this storm is trending towards weakening considerably as it moves into CA and runs into the back side of the ridge over the West.  Taking a look at the GFS ensembles probably forecast, it shows less than a 50% chance of seeing up to half an inch of liquid from the storm now.  

probability

Here is a look at the Canadian total precip forecast through Monday.  Much drier than it was yesterday.  

gfs precip

The Canadian is driest with up to 0.15 inches of total liquid along the crest Sunday night.  The European is the wettest with up to an inch of liquid.  The model average is now down to 0.58 inches.  That gives us the initial snowfall forecast below by Monday afternoon.

forecast

But, the trend is towards a weaker storm.  You can try to go off one run of a model that comes in wet, but look at the average, the ensemble mean runs, and the trend.  The trend is your friend when forecasting.  In this case the trend is not our friend for snowfall...

Extended Forecast

High pressure will build in over CA behind the storm by Tuesday.  That should bring us a drier and less active pattern through the middle of next week...

ridge

The effects of the MJO on the pattern helping to keep a trough in the Northeast Pacific may wane going beyond the 20th.  The long-range ensemble mean runs still show a ridge building over the Canadian west coast later in the month.

ridge in NW

The control runs are even stronger and showing a trough over the West and high pressure helping to drive cold air into the West the last week of the month.  

We will have to keep watching to see if that translates to some storms dropping down from the North into the trough and if they track far enough west to reach the Sierra.  We will also have to watch to see if storms will push under the ridge into CA.  Right now the long-range model runs show a fairly dry pattern, but we can't trust them more than a week out, especially during a pattern change.  But no storms of significance on the horizon right now.

Stay tuned, pray for snow...BA

About Our Forecaster

Bryan Allegretto

Forecaster

Bryan Allegretto has been writing insightful posts about snow storms for over the last 15 years and is known as Tahoe's go-to snow forecaster. BA grew up in south Jersey, surfing, snowboarding, and chasing down the storms creating the epic conditions for both.

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