Wednesday Oct. 22
A low pressure system in the Gulf of Alaska is poised to send two bursts of energy into Northern California this week, with the first bringing just a slight chance of rain to Tahoe and the second more promising for precipitation.
The first pulse is due Thursday as moisture from the low briefly sags south into Northern California. Most of the energy from this piece of the system will be aimed at Southern Oregon and far Northern California, with Shasta and Lassen getting rain and perhaps some snow. Very little of this moisture will find its way south of the I-80 corridor and into the Tahoe Basin.
The low will then retreat into Oregon for a day and Friday should be mostly clear and a bit warmer. Then the trough off the coast will move inland late Friday and bring a much greater chance of rain and snow to the region during the day on Saturday.
It looks like as much as a quarter to a half an inch of rain could fall in Tahoe on Saturday, with rain amounts decreases north to south and snow levels at or above 7000 feet.
The system should be moving through by Saturday night, with perhaps some scattered showers lingering into Sunday on the backside of the exiting trough, mostly north of Tahoe.
After another break it looks like we could see more rain by the middle of next week.
Tuesday Oct. 21
More active weather ahead for the Tahoe basin.
A rather complex storm system is setting up in the Gulf of Alaska and will be moving in waves into Northern California starting Wednesday night or early Thursday morning.
The first impulse will be something of a tease, as a piece of the main trough temporarily sags south and brings a threat of rain and high elevation snow to the Northern Sierra. It looks like most of that precipitation will remain north of the I-80 corridor but we could see some showers in the Basin and on the surrounding peaks.
That storm will then retreat to the north while we will likely remain dry later Thursday into Friday.
But after that pause in the action, the main trough is forecast to move inland Friday night and Saturday. And that’s where the real action could be.
The image above shows the precipitation forecast for Friday through Sunday (click on the picture for greater detail). As you can see, the weekend storm is currently forecast to bring several inches of precipitation to Southern Oregon and extreme Northern California. NWS forecasters are actually using the term “atmospheric river” to describe what’s in store for Oregon this weekend. Even some parts of Mt Shasta could see three to five inches of rain, with snow at higher elevations. The probability of heavier precip tails off pretty quickly as you move south, however, with the Tahoe Basin still in the rain zone but for much smaller amounts — probably around half an inch to an inch. It’s too soon to pinpoint snow levels but it does look like this storm will be on the warm side, so we’re not expecting much if anything below 7000 feet at this point.
There’s also an intriguing conflict in the forecast models, with one of them suggesting that this storm will split as it moves inland, and much of the energy will drop further south, toward Mammoth, leaving Tahoe in the middle between the two pieces of the system that remain in tact. So we will have to keep our eye on that possibility over the next couple of days.
Monday Oct. 20
Another modest cold front is moving into Northern California this morning, bringing light rain to the coast and the coastal mountains and soon to much of Northern California.
The system is expected to reach the Northern Sierra this afternoon, with between a quarter-inch and a half-inch of precipitation possible by Tuesday morning. Most of the rain will fall north of Interstate 80 but there’s a decent chance of some showers south of there in the Tahoe Basin and along the Sierra Crest. Snow levels should be above 7000 feet.
Tuesday will be cool behind the front but temps will rebound Wednesday and should remain at or above normal for a day or two.
Another, potentially larger storm system is taking aim at Tahoe and the Sierra later in the week.
This low pressure system will move into the Pacific Northwest and Oregon as early as Wednesday night, but the first wave of precipitation looks like it will be confined to the far Northern Sierra. By Friday or early Saturday the forecast calls for the system to sag southward, bringing rain and high elevation snow to the Central Valley of California and the Tahoe Basin.
We’ll keep you posted on the details as they develop.