Tahoe Daily Snow

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By Bryan Allegretto, Forecaster Posted 5 years ago October 25, 2018

It's Only October...

Summary

- Sunny and mild weather expected through the weekend, with highs in the 60's and gusty winds as a cold front approaches. - A cold front brings cooler weather for next week with high temperatures dropping into the low 50's at lake level. - We are watching the week of the 5th to see if the high pressure ridge could weaken or shift, allowing storms to push south into CA.

Short Term Forecast

There is not much change in the forecast over the last several days.  We are stuck under a high-pressure ridge that is keeping us mild and dry.  

We will see a change by Monday as a trough and associated cold front push through the Pacific NW. 

trough

We are not expecting any moisture with the cold front.  Just colder air by Monday. 

cold air

Next week we will see a ridge in the eastern Pacific and a trough over the West.  We will be in between the two, but it may be far enough west that we continue to see cooler air through next week as storms dive down into the Rockies.  That could allow the ski resorts to make snow several nights next week.

more cold

The storms the next 10 days will be hitting the Pacific NW and then diving into the trough over the Rockies.  So that is where all of the precip and snowfall will be.

snowfall

Extended Forecast

We have been watching the week of the 5th to see if the pattern could change with the ridge weakening, flattening, or shifting, and allowing storms into Northern CA.  If you are watching each run of the GFS or other models you will just give yourself a headache.

I had an interview this morning from a reporter that wanted to talk about the emotions people go through that watch each model run, haha.  I would suggest running the ensemble mean runs of the models for heights or precip to see what the average of all the models are showing more than a week out and see if they agree with the other ensemble mean runs.  Then compare the operational model runs against that.  Then maybe compare that to the teleconnection forecasts and what those usually mean for the pattern to see if they match up.

That may help to level out the emotions of single model runs.  That way you can see what direction the overall pattern may be heading.  The more agreement among the models the better chance that is where the pattern is going.  Then if they are in agreement and consistently showing a storm and that makes sense given what the upcoming pattern might be, then maybe get excited about seeing a storm.  But I would still wait until you see it consistently, in agreement, and within 7 days to start telling all your friends it is going to snow...haha.

Case in point is the week of the 5th.  The long-range GFS ensemble mean runs average out 22 different model runs.  That model shows a weakening and flatting of the ridge the week of the 5th.  Which would make it easier for storms to push in even though the run to run of the operational model are not showing a specific storm.  The European ensemble mean runs average 51 different model runs and is leaning towards a trough that week.

trough possibly

That will make it even easier for storms to push further south into Northern CA.  Looking at the latest GFS operational model run the 2-week precipitation forecast looks like this...

gfs

That keeps us dry with the storms just to our north over the next 2 weeks.  But looking at the ensemble mean run of the 22 GFS models we have this...

gfs ensemble mean

That average is coming from these runs below.  I circled the wettest.

gfs ensembles

About half of the models have precipitation making it as far south as Tahoe from the 5th - 10th of November.  The flattening ridge on the GFS ensemble mean run and even better the trough on the European ensemble mean run, agree that we are in a pattern that could allow storms to push further south into Northern CA that week.

Then, looking at some of the teleconnection forecasts, we see that the PNA (Pacific north American) pattern is forecast to trend negative during that time.

pna

Which is a pattern that has a trough near the West Coast and storms can drop further south.

pna negative

And, the MJO (madden julian oscillation) forecast has it becoming more active as it cycles into phases 1 & 2 during that time.

mjo

Which historically leads to a better chance of above-average precipitation this time of year...

mjo comps

So I would still watch the week of the 5th as I also stated in the last post.  To me, there seems to be enough to indicate that there will be a better pattern for storms than what we have been seeing.  Not a great pattern yet, but better.  So I wouldn't ride on each run of the GFS or other models.  Let's see whether or not they get stormier as we get closer.  

I don't usually go through all those steps like that.  But I know a lot of people are getting anxious for Winter and watching every model run.  I just thought I'd try to post a few suggestions for looking towards where the pattern is headed so you don't get caught up in the emotions of each run.  There are more models to look at, techniques to use, and patterns to watch, but those are just a few that may or may not be helpful, or maybe you have a better method.

For now, we wait for Winter to arrive.  We are only a few weeks out from the ski resorts trying to open before the Thanksgiving holiday.  The colder air next week should help with snowmaking, and then hopefully the models trend stormier for the 2nd week of November so that we can get some natural snow as well.

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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