The storm that we saw move in yesterday to our North is already moving out this afternoon. The forecast models are in good agreement on a warm storm for later Thursday into Friday after a nice day on Wednesday. They are a little out of sync for the weekend into early next week, but we should have a colder storm for Sunday with some snow.
Not much change in the forecast this week. The first storm is fizzling out this afternoon and the forecast was accurate showing that the heavy precip over Northern CA would not make it into the Tahoe basin.
Areas of low pressure are diving into the trough off the West Coast this week. The next low will draw up warm subtropical moisture that could arrive by Thursday afternoon and last into the day Friday. Snow levels will be up around 11,000 feet to start and may lower somewhere between 9000-10,000 feet by Friday. So this is mostly a rain event.
The GFS forecast model runs show most of the precip staying west and South of the Tahoe Basin with up to an inch along the crest.
Being that the precip is coming up from the South I tend to lean towards the European forecast model that shows up to an inch of rain across the entire Tahoe Basin. So nothing as heavy as what we saw last week, but some moderate rain Thursday into Friday before it tapers off.
You can see on the snowfall forecast that the snow stays well to the South over the highest Sierra peaks.
Then the forecast models start to diverge. The GFS pushes a front into the area pretty quickly by Saturday morning ahead of the next area of low pressure approaching the coast. This is a colder storm with snow levels lowering to 7500 feet by Saturday morning.
Again I will lean towards the European forecast model that holds off on precip until Sunday, as it has the agreement of of forecast models as well. So we may have a break on Saturday before a colder storm moves in off the Pacific on Sunday.
The GFS has 2 inches of additional precip with the 2 day storm, while the other forecast models have closer to an inch.
Snow levels should drop pretty quickly with the storm below 7000 feet and possibly near lake level on Sunday. That could mean up to a foot of snow is possible around 8000 feet with 6-9 inches at 7000 feet, and few inches possible to lake level if the snow levels come low enough fast enough.
You can see the difference on the snowfall forecast with the 2nd storm, although this is the GFS which is a little heavy on the snowfall as it starts Saturday instead of Sunday. It shows about double what the other models show.
So we will have to keep an eye on the weekend forecast to see if the GFS has any merit, and to see how much snowfall we could get.
The GFS model is on its own again as it shows the storms coming far enough South next week to bring mountain snows Monday, Wednesday and Friday. The rest of the forecast models show the storms weakening or staying to our North all week not bringing us much in the way of any precip. Temperatures will be cooler with the active pattern.
The long-range forecast model runs show less active weather going into November. Let's hope that is not the case. The European weeklies show a ridge wanting to sit near the Canadian coast later in November and into December.
The CFSv2 shows a flatter ridge sitting off the West Coast with more of a classic weak La Nina pattern with the Pacific NW down to Northern CA having equal chances of average precip, and dry for Southern CA. We are right on the line similar to the pattern next week.
It keeps a similar pattern through the Winter...
The good news is that the CFSv2 historically has not been a very good model in the long-range. I'm wondering if the Euro is not onto something with the ridge further North where the CFS is wet, and storms cutting underneath at times into CA.
Last year we saw a pattern opposite to that of a typical El Nino with CA dry and the Pacific NW wet, could we see an opposite pattern again this Winter? There are a lot of confusing signals for forecasters this Winter. There as some claiming that the warm SST's in the Northeastern Pacific have no affect on the West Coast weather pattern, but they can't explain why it appears to have had an effect looking at the last 100 years of records.
I'm still not confident in the La Nina forecast. It is very weak and I'm not seeing any conditions that support it strengthening. This Winter's pattern may be controlled by other oscillations like the Arctic Oscillation that has been very negative this fall which helps to setup blocking patterns to the North. We will also watch how the Northern Pacific SST's could affect the pattern, and the MJO as we get into Winter. Just not seeing how the weak La Nina will be in control this Winter.
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