After suffering through the driest year on record—some say the driest in 500 years—a significant storm is on the way to the Eastern Sierra this weekend.
Although the bulk of the incoming storm will go north of Mammoth, Mono County is still on track to receive anywhere from two to four feet of snow, beginning Friday afternoon and continuing into Monday, according to the National Weather Service.
At the time of this writing (around 1 p.m., Friday, Feb. 7) the incoming storm had already blanketed Oregon and Washington with as much as ten inches of rain and snow and was headed south, pointing an "atmospheric river" of moisture at the Northern California coast and the Sierra Nevada.
An atmospheric river is a big, concentrated plume of moisture within a storm track.
According to Scott McGuire, a meteorologist with the National Weather Service, the storm will come in on three waves, beginning Friday and finally tapering off sometime on Monday.
The big unknown is exactly how much snow the region will get, but he said the Mammoth area is in for a “significant precipitation event.”
“It’s a tricky forecast when dealing with snow levels,” he said. “You won’t get as much as the western slope of the Sierra, where they are forecast to get about ten inches of moisture (this could be about eight to 10 feet of snow at very the highest elevations there), because you are south of the bulk of the storm, but you are on tap to get some much needed moisture. The good news for Mono County is that you are a relatively high county, as in high elevation. That will compensate somewhat for the fact that you are south of the main storm track.”
The colder the storm, the more snow per inch of moisture there generally is, or the higher the elevation at which the precipitation comes in, the more snow per inch of moisture there is—something called the snow-to-water ratio, he said.
However, in this case for the Eastern Sierra, the system is forecast to be fairly warm, which will decrease the snow-to-water ratio.
The storm will come in beginning Friday and continue into Friday night, bringing light snow and a lot of wind, he said.
The next wave of the storm is the biggest wave, coming in on Saturday morning heavy and wet, and continuing throughout Saturday, with another wave coming in Sunday and into Monday.
Mammoth’s amateur weather forecaster, Howard Sheckter, puts it like this: “The blend of models suggest three to four inches of water up on the pass,” he wrote in his Friday morning post. “With orographics, you can never get it exactly right and so it may end up more, so the three to four inches is probably a bit conservative. This means that considering the freezing levels and the low snow to water ratios, the upper mountain (Mammoth Mountain Ski Area) should be in for a good two to three feet by Monday morning.
“In town the most snow will fall Saturday morning and it could be five to six inches before the freezing levels go to 9,000 (feet) that afternoon and 9,500 Saturday night. The snow level will be about 8,000 Saturday afternoon and 8,500 Saturday night into Sunday afternoon.
“It comes down later Sunday night and so will the snow level. Strong winds will accompany the storm with gusts in town Saturday morning in the 50 to 60 mph range.”
In the long range, another smaller system is forecast for the area Wednesday and then, perhaps, another larger storm system next weekend, McGuire said.
“You will have another active weekend next week,” he said. “Again, it’s tricky to forecast so early, but it will be a decent system. If it goes north of you, that would change lessen the amount of moisture you receive, but it is still a decent system.”
The news for the Southern Sierra and Inyo County this weekend, however, is not nearly as promising.
“Right at the Inyo County border, the moisture content tapers off,” McGuire said. “Bishop might be on track to get about a quarter inch of moisture and the high crest of the Sierra some snow. But they will not get anywhere near what Mono County will get.”
After that, he said, the big, high pressure ridge that has blocked an entire winter’s worth of storms and is now off the Baja California coast for the first time, instead of off the West Coast, could come back.
“It’s trying to be pesky,” he said. “It’s trying to jog back north.”
That could mean the region will dry out again after Presidents Day weekend, he said.
Or perhaps not.
“There is also a large, low pressure system in the Gulf of Alaska that will battle with the ridge then,” he said.
“We will have to see who comes out on top.”
The incoming storms are welcome news to the West Coast states, but McGuire put it in perspective.
“We need four or five of these kinds of storms to bring us up to normal precipitation,” he said. “Tahoe City still has a 30 inch precipitation deficit since last January and even after these storms, that will leave a big deficit.”
The same goes for the Mammoth Mountain area, which should have received about 26 inches of precipitation—or somewhere between 15 feet to 26 feet of snow—by this time this year.
Instead, Mammoth Pass has received 8.4 inches (as of Feb. 3), according to Los Angeles Department of Water and Power data.