Steadier rain and snow move through Saturday into Saturday night, with snow levels falling Saturday night. Clearing and cool on Sunday. Dry and milder weather is expected through Wednesday. We could see a cold front for Thanksgiving and maybe a few snow showers, but overall no significant storms are on the horizon through the end of the month.
Short Term Forecast
We have been watching a low-pressure system spinning near the West Coast over the last few days. That has brought some rain and high-elevation snow showers to the northern Sierra through Friday night. We've seen a few inches of wet snow accumulate above 8000 ft.
Saturday Rain & Snow:
As of early Saturday morning (5 a.m.), the center of the low is still off of the coast of CA (the "L" in the radar image below) with a band of heavier precipitation on its east side finally pushing closer to the Sierra.
That will continue to push east as the low moves inland through CA on Saturday. Precipitation will continue to increase through the morning and into the afternoon. That will bring some heavier rain and high-elevation snow to the northern Sierra.
Freezing levels (where the temperature is 32 degrees) are around 8000 ft. early Saturday morning. They are forecast to stay in that range through the afternoon. With the lighter showers that would put snow levels up around 7500-8000 ft. and then dragging to near 7000 ft. under heavier bands through the afternoon.
We could see around 1-4 inches of wet snow between 7000-8000 ft. from west to east across the basin and low to high in elevation, and 2-6 inches of snow above 8000 ft. by Saturday evening.
Saturday Night Snow:
Saturday evening a cold front moves through behind the low and continues the precipitation, with a band of heavy precipitation expected with the frontal passage. Then snow showers behind the front that clear out by Sunday morning. Here is a look at the forecast radar for Saturday through Saturday night.
This is when things become more interesting as colder air is finally introduced to the storm with snow levels dropping to near lake level during the evening and most likely by midnight. How fast snow levels drop will determine how long we see snow for the lower elevations.
The latest model runs continue to show most of the precipitation with this 4-day storm falling Saturday into Saturday night at the end. The main event after only rain and high-elevation snow showers so far. The latest forecast model runs show 0.9 - 1.6 inches of additional liquid falling near the Sierra crest to the west of the lake, with the highest amounts northwest near Donner Summit.
Most of the ski areas fall on or just west (see image in the announcements), with just a few on the east side of the lake/basin. The latest model runs show up to an inch of additional liquid falling to the east side of the Sierra and Tahoe basin Saturday through Saturday night. The WPC's blended model shows the higher end of the forecast.
The main point to get across is that heavier rain and snow are yet to come with this storm through Saturday evening. Snow levels drop below 7000 ft. during the evening, so any mixing near to just above 7k' will turn to all snow. Then all snow to lake level and possibly below 6000 ft. by the end early Sunday morning.
The snowfall forecast hasn't changed much from Friday morning. I have 0-3 inches for lake level depending on how fast snow levels fall as the precipitation moves out of the region. The best shot at higher amounts would be west of 89. For the mountains, I have 24-hour snowfall totals by Sunday morning of 2-9 inches above 7000 ft. and 4-12 inches above 8000 ft. with the highest amounts NW of the lake.
We'll do our best to get some ski area reports on Sunday morning, but with most ski areas still closed it will be hard to get a lot of reports to verify the snowfall. Some ski areas have already announced delaying opening this upcoming week. I would think if they see several inches up to a foot of base-building snow and colder nights for snowmaking behind the storm, they will be in better shape.
Sunday - Wednesday:
We will clear for Sunday with mostly sunny skies expected through Wednesday. We start off on the cooler side through Monday with highs in the 30s on the mountains to near 40 degrees for the lower elevations near lake level. Then it warms into the 50s near lake level for Tuesday - Wednesday as high pressure builds over the region.
A cold front is still expected for Thanksgiving, but a back door type front from the north and east as a cold trough digs south into the West.
That would be a dry track for the cold front with not much of a moisture source to produce snow over the mountains, but the latest model runs still show some scattered snow showers are possible.
Maybe some ambiance snow for Thanksgiving along with colder air and highs dropping into the 40s at the lake and 30s for the upper mountains.
If we see colder air move in on Thanksgiving that should also give us some colder nights by the end of the week for better snowmaking at night. The ski areas are depending on that so far this fall with the lack of early-season snowfall.
Other than scattered snow showers possible on Thanksgiving, there's really nothing else showing up on the long-range models for storms through the end of November, and even into the first few days of December. The ensemble mean models all show well below-average precipitation starting tomorrow (Sunday).
Looking out into the first week of December I'm still not seeing the jet stream forecasts over the Pacific showing much signs of an El Nino influence. The jet doesn't look very strong and the strongest winds stay well off the West Coast.
The height forecasts show lower heights over the southwest, similar to an El Nino pattern, but we are waiting on stronger storms to blow into the southwest and CA. That normally would start to happen as we go into December, especially by mid-month. During El Nino seasons we've seen on average the most snowfall in January with December being the 2nd most, followed by February and March.
So I am expecting things to ramp up in December, and possibly pretty quickly beyond the current 2-week outlook period. Let's hope...