Summary: 

Quiet weather through the weekend with highs in the 50's.  The weather will change dramatically next Tuesday as a very cold front moves through bring much colder air for the rest of next week.  Highs will only be in the 20's at lake level and teens on the mountains through Thanksgiving.  The cold front Tuesday could bring several inches of snow down to lake level with a foot or more on the mountains.  The snow showers should continue Wednesday and Thursday before we have a break on Friday.

Several Pacific storms will be lined up off the coast by next weekend that could move into CA starting Saturday the 28th and continuing into the first week of December.

Details:

We will be playing the game of storm track over the next several days for the low next week moving down the West coast.  The models over the last 24 hours have shown the low coming down the Sierra, down the coast just inland, and down off the coast.  The track of these lows is critical in how much precip is pulled in off the Pacific.

What we do know is that a cold trough is going to push down from the North with the initial cold front arriving by Tuesday.  We also know that the cold front will generate at least several inches of snowfall and will usher in very cold air, the coldest of the season so far.  The question will be for Wednesday and Thursday where does the center of the circulating low pressure track down the coast Wed-Thu?

Yesterday's post went into more details about the pattern for next week and it also showed the high end potential for next week with the low tracking down just off the coast pulling in waves of moisture Wednesday and Thursday after the cold front on Tuesday.  Some of the model runs yesterday afternoon started dropping the low down well inland and pulled way back on precip amounts.  This morning the forecast models are in decent agreement with the low dropping down just inside the coastline over land, with moderate amounts of snowfall possible.   The forecast will most likely change several more times as we are still 5-7 days out from the event.

Here is the latest GFS total precip forecast.

Right now most of the snow is expected to fall on Tuesday with the cold front.  We could see several inches of snow at lake level with up to a foot on the West side West of highway 89.  For the mountains up to a foot of snow could fall above 7000 feet, with up to 18 inches along the crest West of the lake.  That is based on an average of the latest GFS and European forecast model runs.  Behind the front the snow ratios jump with the very cold air.  With the over land track only expecting very light snow showers Wednesday and Thursday, but with high snow ratios.  We could see a few more inches accumulate during the 2 days at lake level and several inches on the mountains.

I don't want to get too into the snowfall forecast details yet as this will probably change a few more times as we get closer and the track of the low changes from run to run of the models.  Just count on very cold air and snow, with the best chance for heavy snow Tuesday and snow showers through Thursday.  Thanksgiving the snow showers should start to end.  If the low ends up tracking further off the coast then we could see heavier snow Wednesday and Thursday.

Long-Range:

We also need to start looking at the forecast for the following weekend and into the first week of December.  The ridge looks to shift into Canada by the weekend with a couple of storms that may try to move underneath into CA.  The question right now looks to be if the storms track into Northern or Southern CA.  

Going into the first week of December the ridge may move over the Central U.S. as a large trough sets up on the East Pacific.  That may continue the active storm track into the West Coast.

Stay tuned....BA