Summary:

Quiet and Sunny weather expected for the next 7 days with highs in the upper 40's to low 50's.  Next week a cold trough may dig down the West Coast bringing a return of cold air starting Tuesday.  Low pressure may also move down from the North and the track could mean a chance for light snow, or a chance for significant snowfall through the Thanksgiving holiday.  You will want to stay tuned moving forward.

Details:

First, let's recap the last storm.  Here is a look at the final totals reported by the ski resorts.  As expected the heaviest snow got hung up along the crest with the orientation of the front.  As an example driving through Truckee and along Donner Lake yesterday there was a coating to an inch of new snow.  Once to the office on top of Donner Summit we had 5 inches of new snow.  The same on Sunday as I drove the North end of the lake with a coating of snow and an inch along highway 89.  As I drove into Olympic Valley the snow got deeper with 4 inches on the ground Sunday afternoon in Squaw Village.  You can see the same for the mountains on the East side of the basin 2-6 inches (Heavenly, Diamond Peak, Mt Rose) vs the West side 8-14 inches.

 

Looking at the total precip so far this water year starting Oct 1st the Northern Sierra is only at 67% of average.  Even though we have had early snow it has been light amounts by Tahoe standards.  We are actually behind this time last year.

The snowpack survey hasn't been updated since the 13th.  What is interesting is that even though the influence of the El Nino on the pattern is expected later in the Winter, the total precip amounts so far look like what we would expect this Winter with more over Central CA.

and even more above average over South CA so far...

Nice weather through the weekend as the ridge of high pressure sits off the coast and the storm track stays to our North.  There will be inversions at night with colder air in the valleys and warmer air in the higher elevations.  That may mess with snowmaking on the mountains.

In the last post we were looking at high pressure sitting off the coast in the East Pacific next week on most model runs keeping us dry.  We did however see the GFS hinting at a more amplified ridge and the possibility of colder air driving down from the North by Thanksgiving.  I left off the post with this, "Let's hope that the ridge at least amplifies North far enough off the coast over the next 2 weeks to at least bring us colder air, and maybe some moisture off the Pacific for some snow."

In the last 24 hours the GFS has continued to amplify the ridge further North next week and shift it a bit further West.  That would help to drive a cold trough down the West Coast.  It also started showing a low forming along the West Coast and slowly moving South down the coast next week drawing Pacific moisture into CA and the cold air.  I've seen this pattern happen before and bring us big snow so that is why I alluded to it at the end of the last post.  Hope's coming true?

We can't be sure this far out, but the Canadian and European ensemble runs are beginning to trend towards the GFS.  That doesn't necessarily mean big snow, but much colder air should be a better guarantee.  We will have to watch how far West over water the trough digs and low pressure sits as to how much moisture it pulls in.  If it tracks down over us or to the East like some model runs show it could just be a light dusting with the cold front.  If it slowly drops down along the coast like the last few runs of the GFS, then there is a potential for significan snow through the Thanksgiving holiday.  We will be watching closely.  

Ok enough of the words, I have lots of pictures today.  I didn't post yesterday so I have 2 days worth of accumulation.  I am looking at the weather all day everyday and when I see something interesting I capture it to show you.  Here is pretty picture painted by the 0z GFS showing the potential snowfall if everything comes together just right, fingers crossed....

This would however mess with Thanksgiving travel plans in the Sierra, including mine.  I usually drive up 89 from Truckee up through Lassen park, and then drop down to the in-laws house in Redding.  It's a beautiful drive but when there's a storm it can greatly increase the drive time which is no bueno with a car full of young children...

Here is a look at the Canadian ensemble mean forecast for the height pattern from Sunday for next week.

Now look at the latest run, the ridge is further North and West.  The trough comes down over CA.  A cold pattern with light snow possible.

Here is the GFS ensemble forecast.  Notice the trough is further West along the Coast and the strong low sitting off NorCal.  

So this is a good trend by the forecast models for next week if you want cold for Thanksgiving, and starting to look better for snowfall.  We will be watching closely moving forward...

The El Nino update came out yesterday.  Although the area of above average sea surface temps is narrower than 97', Nino 3.4 did reach "Godzilla" zone at 3.0 degrees celsius above average this week.  That makes it the strongest ever recorded in region 3.4 which is the region used to track El Nino strength.

This strength is still brief so far but should continue.  Looking at the ONI (Oceanic Nino Index) which is a 3 month running average of Nino 3.4 were are running about a month behind 97' as of the end of October.  We were at a 3 month average of 1.7 which we hit in September of 97, and one month ahead of 82 which hit that average in November.

Every week and month the climate models update with the new actual sea surface temp data and forecasts.  What I have seen the last 2 weeks is cooling of the warmest water off the baja, and warming of the cold pool North of Hawaii.  The entire Eastern Pacific seems to be mixing into one equally warm area.  We talked about what the latest data did on the 10th to our updated snowfall forecast on the opensnow forecast model.  It dropped the snowfall for about 2% for Tahoe resorts, but still has near average to about 30% above average as the range.

Looking at some other climate models there are a few changes.  Last month I mentioned that 3 of the 9 NMME models were showing us on the border of average to below average precip Jan-Mar.  Now all 9 have above average precip for our region with the the dry models from October pushing the above average precip further North into Northern CA.

The CPC forecast for January to March is also a bit further North with the above average precip as well, even touching into Southern Oregon.

The climate models are still mixed for December showing equal chances for precip.  It looks as if a large trough may try to carve its way into the Eastern Pacific during the 1st week of December replacing the ridge.  That may continue an active storm pattern.  The unreliable CFSv2 model is showing above average precip by the 2nd week of December.

So for now we wait and watch for the next several days.  If anything the weather shouldn't be boring moving forward, just tricky.

Stay tuned....BA