ALL BETS ARE OFF
After one of the driest years on record in the Sierra Nevada, the region desperately needs a consistent snow year to alleviate parched lakes, rivers, and landscapes.
A number of strong storm systems in October provided enough snow to open Mammoth Mountain two weeks early. The question remains: were those early storms a sign of more to come or a red herring leading into yet another dry winter?
Chris Smallcomb, a meteorologist with the National Weather Service in Reno, gave a presentation to the Mono County Board of Supervisors on Tuesday that aimed to address that very question, among others.
Smallcomb said that summer 2021 set records for heat around the region, state, and country, solidifying the existing drought conditions.
Before answering any larger scale questions, Smallcomb delved into the October storms, what they mean for the area, and what those storms may indicate for the season as a whole.
From October 23-25, the Eastern Sierra experienced what Smallcomb termed a “super mega atmospheric river” that produced a lot of rain for the region and was “largely a beneficial event” from a hydrological standpoint.
For an event such as this to occur so early in the season, he said, was “really unusual,” going from a hot summer to a sudden winter storm.
Smallcomb used Lake Tahoe as a reference point for the storm’s impact, stating that the lake is “a really good gauge of how hydrology in the environment is doing.”
Water levels in Tahoe rose half a foot as a result of the storm, marking only the 8th time in 121 years where the lake has seen a net-rise in October. Reno Airport received 2.92 inches of rain, good for 40% of the annual average precipitation at that location and nearly matching the entire 2020-2021 water year total of 3.02 inches.
Bodie received 2.22 inches of rain in two days, the 25th highest two-day total since the 1950’s and the highest two-day total ever in the month of October.
“Does this help the drought?” he asked, “No, drought is still a factor. We need a series of decent storms.”
That said, there were some positive outcomes already for the water year. The October storm system moistened soil considerably, “going from near-record dry levels to near-record wet levels,” according to Smallcomb.
“When we get our snowpack this winter and start melting it off,” he continued, “that melt-off will go right into streams, creeks, reservoirs, instead of going into parched soils.”
There is a caveat: recent fire activity has loosened soils in the region, increasing the overall likelihood of severe flooding/mudslides.
Smallcomb said that it [flooding] could be “a serious issue for our region in the next 2-3 years.” 0.1-0.25 inches of precipitation in 15 minutes would be enough to trigger debris flow and mudslides, he said.
Smallcomb said that for the next few days and weeks, there is “not a whole lot going on around the Eastern Sierra, just very light, innocuous events” up through about Thanksgiving.
Things may change in December, according to Smallcomb, who said that there are signs of the atmosphere “waking up again” at that time. Storms systems would start sagging back south from the Pacific Northwest and the odds of an atmospheric river are already increasing.
He displayed a pie chart of the projected precipitation outlook for the Sierra Nevada that reported 33% likelihood of an average winter, 33% likelihood of an above-average winter, and a 34% likelihood of a below-average winter
The official forecast: “Anything is possible at this point for the December, January, February period,” Smallcomb said, “There’s a very slight lean towards drier-than-normal but it’s a very soft signal.”
“I’ve seen my fair share of wet Octobers become very active winters,” he said, adding that it’s not a 100% correlation but “enough to raise my eyebrows a little bit.”
A lack of snow in November isn’t an indicator for the rest of the season. Smallcomb said that he saw similar pattern, wet October into dry November, in 2016; the following January, Mammoth Mountain received 245 inches of snow.
