Tahoe Daily Snow

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By Bryan Allegretto, Forecaster Posted 6 years ago October 18, 2017

Little Wetter, Little Colder...

Summary

Today will be the last warm day with light winds. Thursday the winds and clouds increase ahead of the next storm, with highs in the 50's. Thursday night into Friday we will see a storm move through with wind, rain, and snow. We could see several inches of snow fall above 9000 feet, a few inches down to 8000 feet, with a dusting down to 7000 feet. A few flakes not out of the question at lake level Friday morning but not expecting accumulations. Highs only in the 40's at lake level for Friday. High pressure builds in over the West this weekend and into next week bringing a week of warming and dry weather, with highs well into the 60's. There are signs that we could see a pattern change around the end of the month, 28th-30th. We will keep watching that for the next chance of cooler air or precipitation.

Short Term Forecast

We have some minor adjustments today on this storm we have been tracking for 2 weeks now.  This time of year there is plenty of time to track storms as they are just getting started.  I hope you have all been out enjoying the Fall weather this week.  It has been really beautiful, especially with the Aspens changing color.

The Storm:

The last few runs of the models last night into this morning have slightly increased the amount of precipitation for the storm tomorrow night into Friday morning.  They have also sped up and lowered the colder temps moving in with the storm slightly.  

Here is a look at the latest GFS model run showing up to 8 tenths of a inch of liquid with the storm West of the lake along the Sierra crest.

gfs precip

This is the wettest model run I've seen today but the trend is to increase the precip amounts slightly with each run, so we will have to keep watching over the next 24 hours. 

Here is the European ensemble run average showing that the 50 members averaged has only up to half an inch of liquid near the crest and half that for the East side of the lake.

eps

It looks like the precip could move into most of the Tahoe basin between 10 p.m. and midnight, and a bit earlier for the crest and NW of the lake.  The freezing levels are forecast to be running around 10,000 feet at the start, and with a cold front passage like this the snow levels can run around 1,000 feet lower than the freezing level, so snow levels could start out around 9,000 feet.

freezing 1

This was expected all week, but the difference this morning is that the forecast shows colder air cold move in before the storm moves out by midday Friday.  We could see snow levels drop close to lake level by Friday morning.

freezing levels 2

Looking at the latest GFS model run you can see that at 4 a.m. the precip should still be falling before ending by noon across the basin.

gfs

So that means there is a little bit of a snowfall forecast to be had this morning, although not that big of a deal since the ski resorts aren't open, it won't be enough to ski the back country, and it will melt this weekend...  

Snowfall Forecast:

Right now it looks like we could see 3-6 inches of snow at 9,000 feet on the West side of the lake, with 1-3 inches at 8,000 feet, and a coating down to 7,0000 feet.  Not expecting an accumulation down to lake level or 6,000 feet.  I would cut that forecast in half for the East side of the lake.  

We will have to keep watching the model trend over the next 24 hours to see if they are drier, wetter, or the same.  I would not expect them to get much wetter.

Post Storm Weather:

This weekend high pressure begins to build in over the area with a pretty strong ridge of high pressure over the West by next week.

ridge

That will bring warm and dry conditions, even to areas to our North that will get a lot of rain and feet of snow on the mountain tops this weekend.  High temperatures should be back into the 60's and pushing 70 possibly at lake level.

Extended Forecast

2 Weeks:

The long-range forecast is holding some hope today that we could see a pattern change by the end of the month.  We will be watching a strong MJO signal move through the Western Pacific and we will be watching the typhoon activity to see how it could affect our pattern later in the month.  For now the long-range model runs do show the possibility of a pattern change around the 28th-30th.

Looking at the ensemble runs of the models they do show the possibility of a trough in the Gulf of Alaska by the end of the month and trying to dig down the West Coast.  Here is the GFS ensemble mean run.

gfs ens

The mean runs of the models seem to be shallower with a month-end trough, while the control runs of the GFS, European, and Canadian models seem to be deeper.  It's still 10+ days away, but a sign we could see a pattern change the end of the month and into November, but of course like I said above there are other short-term factors that could affect the pattern by then as well.

November:

Looking at the European weeklies forecast that came out on Monday it does show a pattern of ridges and deep troughs moving through the West.  A pretty progressive pattern.  Looking at the CFSv2 for November it is showing average to above average precipitation for the West Coast.

November

These long-range forecasts are not very accurate, but maybe November will get us going with some real snowfall?

The Season:

A couple weeks ago I put out a forecast for the Winter of 80-90% of average snowfall.  Since then not much has changed except that the Eastern Pacific sea surface temps have begun to cool.  Comparing to past years I still like similarities to 95-96 and 11-12.  Looking further West towards the Indian Ocean the sst's look similar to 05-06 and 08-09 weak La Nina seasons as well.  

Here is a look at how those Winters looked for CA, and for Tahoe they averaged 90% of average snowfall.  

snowfall

I like what I'm seeing right now as far as weak La Nina seasons, and I think I am leaning more towards the 90% end of the forecast.  We will have to see more trends this Fall before I make a change from the 80-90% initial forecast.

Looking at the updated Weatherbell Winter forecast they have Northern CA in the average snowfall section with below average just below Tahoe.

wxbell

Accuweather.com is similar...

accuweather

We are right on the above/below average line which is common in La Nina Winters.  Let's hope we stay above the line this Winter.  Still expecting a slightly colder than average Winter and 90% of average would not be that bad when we average 400-500+ inches a season.  But of course this is all just for fun as the Fall forecasts for Winter don't always turn out as expected. 

Stay tuned...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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