Tahoe Daily Snow

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By Bryan Allegretto, Forecaster Posted 7 years ago December 4, 2016

Case Study 2, Heavier Snowfall on Friday...

Summary

Sunny today with highs in the 40's. Gusty winds of 40+ mph for the mountain tops. Colder air moves in Monday with highs only in the 30's with gusty ridge winds continuing. Tuesday a low moves through bringing even colder air and the chance for some light snow showers. Not expecting more than a dusting and highs in the 20's through Wednesday. Gusty mountain top winds should continue. Wednesday night into Thursday light snow could break out as warm air ahead of the next storm overrides the cold air in place. We could see a few inches of snow on the mountains, with snow levels rising above 7000 feet on Thursday. Thursday night into Friday a strong storm could move in with lots of moisture. Snow levels start high Thursday night around 8000 feet before falling to lake level Friday. We could see up to 2 feet of snow on the mountains with this storm and several inches at lake level by the time it ends Friday evening. Stay tuned for updates. After a break next weekend another storm may move in Monday the 12th and another Wednesday the 14th.

Short Term Forecast

We definitely have some changes this morning to the forecast.  We have been looking at 3 case studies that I pointed out on Thursday.  One is to see of we get any snowfall accumulation this Tuesday as the European model shows but not the GFS.  #2 is if we get a wet storm on Friday as the Euro showed and not the GFS, and #3 is if the storms continue the week of the 12th as the Euro showed and not the GFS.

For case study #1 we still have to wait and see on Tuesday if the low tracking down to our Northeast can produce an inch or two of snow.  The GFS and Canadian models are dry and the European model still shows some light snow.

For case study #2 the European seems to be winning as the GFS and Canadian models are now much wetter for the storm on Thursday night into Friday.  Remember that we started this study after the European model crushed the other models with the snowfall forecast for the last storm.

The GFS model runs started getting much wetter in the 12z model run yesterday right after I posted.  Like the European model it keeps the moisture tap across the Pacific long enough to push heavy precip into our area Thursday night into Friday.  Look at the moisture pulling all the way from near Hawaii.

gfs pwat

This shouldn't be as warm of an event as a true pineapple connection would be.  But warmer air will pull in ahead of the storm.  Remember that the coldest airmass so far this season moves in Tuesday into Wednesday, so that cold dense air doesn't just move easily.  The less dense warm air overrides the cold air in place and that rising motion should cause light snow to break out Wednesday night for all elevations  we could see an inch or two of accumulation.

Thursday the cold air starts to erode and snow levels may rise to 7000 feet as the light snow showers continue.  We could see another 1-2 inches above 7000 feet.

Thursday night the river or moisture ahead of the cold front moves into the area.  The latest GFS run shows snow levels rising to 8000 feet. Here is a look at the storm moving in on the GFS Thursday night.

gfs friday

This is a big change from the amount of moisture the GFS was pulling into our area 24-48 hours ago, but it is now consistent the last 24 hours, and we are 4 days out so it's time to analyze the potential snowfall.  

The snowfall forecast of course will be tricky.  It will depend on how high the snow levels go by Thursday night and how fast they fall as the cold front moves through on Friday dropping snow levels to lake level.  Snow showers may linger into Friday evening before the storm moves away.

Here is a look at the total precip forecast from the GFS which is actually now wetter than the European model.

gfs total precip

The GFS shows up to 4 inches of liquid near the Sierra Crest along the West side of the Tahoe basin.  The European model shows close to 3 inches this morning.  The Canadian model is close to the GFS, with a little more spillover to the East side of the basin.

canadian

Here is the initial snowfall forecast through Friday.  I put a legend at the end of the post.

initial snowfall forecast

You can see the drop in snowfall below 8000 feet as I'm trying to account for the snow levels.  The snowfall at lake level comes at the end on Friday.  The GFS coming in so wet is new the last 24 hours and the snow levels will be a pain, so we will be overanalyzing this storm over the next 4 days.

Looking at the ensemble members for Donner Summit Snow Lab (7000') you can see the average snowfall amount by Saturday is around 20 inches.  I have 17" in my table above so I think we have a good starting point for the forecast.

ds plumes

We should have a break in the action next weekend with cold air moving in behind the storm.

Extended Forecast

Case study #3 is to see if the European model was correct in the storms continuing the week of the 12th when the GFS was showing the storms staying to our North.  The European model looks to be winning that as well as the GFS, Canadian, and European models now all show a possible storm for Monday the 12th.  

We are 8 days out on that one so no specifics yet as we don't start to look at specific storms until about a week out.  The idea on the latest runs is that a cold low may move down from the Gulf of Alaska and merge with a low moving East across the Pacific, and push into the West Coast.  If that were to happen we could see another decent storm.  If they don't merge and one goes North we may see a weaker system possible.

Here is a look at the storm on the latest model run.

gfs monday storm

The active pattern may continue with another storm possible day 10.  Like I said in the last post the upcoming pattern does not close the storm door, but the storm track needs to come far enough South to reach us.  Here is a look at the 10 day GFS total precip forecast showing we could have a wet 10 days ahead if everything works out.

gfs 10 day precip

Of course most of that should be snow for the mountains.

gfs 10 day snowfall

Beyond 10 days the pattern still looks like it could have a trough in the Gulf of Alaska and a ridge over the Southwest U.S.  We are caught between an active storm track to our North and dry to our South.  We need to continue to hope that storms can trend further South like they have for the next 10 days.

Don't get too excited about the forecast yet.  We have snow levels to deal with this week, and a storm track to deal with next week.  But we are looking better than we were, and better than the dry pattern we have had over the last week.

Stay tuned...BA

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Geography Key:

East

Mt. Rose, Heavenly, Diamond Peak

Central

Northstar

West

Tahoe Donner, Homewood, Bear Valley, Dodge Ridge

Crest

Boreal, Donner Ski Ranch, Sugar Bowl, Squaw, Alpine, Sierra, Kirkwood

*Boreal and Donner Ski Ranch are forecast with the "West" mountains in higher snow levels events.

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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