Why are Tahoe winters ever-changing?

Snowpacks+in+Lake+Tahoe+are+famously+inconsistent.+The+snow+at+Alpine+Meadows+%28above%29+on+Dec.+9+was+light+powder.

Photo Credit: Kyra Kliman

Snowpacks in Lake Tahoe are famously inconsistent. The snow at Alpine Meadows (above) on Dec. 9 was light powder.

Kyra Kliman, Editor

[Editor’s note: This story was updated to correct erroneous reporting that Squaw Valley closed mid-season in 2015. The resort closed in April that year.]

Longtime Tahoe locals will never forget the relentless winter of 1997. The year of huge snowfall gave way to warm temperatures and massive flooding. Locals and weather experts alike will also tell you that in Tahoe, unusual weather is not so unusual anymore.

Tahoe has been through warm and dry winters, and extremes with record-setting snow. Due to inconsistent amounts of snowfall, Squaw Valley Ski Resort closed in April during the bleak 2014-15 season. It was a different story the next two years: In the 2016-17 and 2018-19 seasons it closed in July, when skiers in T-shirts and sunglasses made turns in 60-degree sunny weather.

The four seasons leading up to 2015 also had below-average snow levels, which had dramatic negative effects on local resorts and businesses. Tahoe City was a ghost-town from a lack of tourism, which was mainly due to the lack of snow. Algae around the lake’s margins were at record-low levels as the water fell by 9 inches, ac- cording to UC Davis Tahoe Environmental Research Center. The lake was below its natural rim for 364 days, where water could not flow into the Truckee River.

The lack of water negatively affected The Pyramid Lake Paiute Tribe, which relies on Lake Tahoe as one of its primary water sources.

It was bad news for Dan Shimmon, who works at The Backcountry, a local ski shop in Truckee, but they had a backup plan. He explained that during the 2014-2015 winter, “the general trend of resort traffic was significant downturn, but we were affected less.” The ski shop leaned on its bike business, which has allowed it to stay in business during the warmer years.

It was a different story in 2017. Squaw Valley and Alpine Meadows set a monthly snowfall record at 282 inches in March. In 2019, it trumped its previous year with 300 hundred total inches of snow in February alone, according to the Squaw Valley and Alpine Meadows snowfall tracker.

But why does snowfall in the Lake Tahoe region vary so dramatically?

“It depends on what storms you have,” Evan Laguardia, a meteorologist at the National Weather Service in Reno, said. There are low pressure systems and high- pressure systems, which depend on moisture transport and storm structure.

Andy Rost, chairman of the Department of Science and Technology at SNC, has a doctorate in hydrology from the University of Reno. He says there is varying weather due to big weather scales. “Were talking about enormous systems, half of the Pacific Ocean and how that system moves negative and positive feedbacks, increase things in different directions,” Rost said. “These weather systems move and change on multi-year scales.”

The current method meteorologists use to determine weather patterns relate to low and high-pressure systems that impact the Sierra. Low-pressure systems circulate counterclockwise, forcing air to go upward and cause precipitation. High-pressure systems circulate clockwise, causing a sinking motion in the atmosphere that causes clear skies and sunny weather.

According to Rost, “There is a Pacific high-pressure system, which parks itself off the west coast of California, and there is a low-pressure system that parks itself off the Aleutian Islands in Alaska.” Those forces power a cycle. There is fluctuation with air, and ocean temperatures affect the variance in the snowpack. The ocean temperatures shift on large time scales from a vast body of water. Rost points out that air temperatures change at much quicker scales, which can happen daily, monthly, and annually. The mismatch of this change in temperatures is another reason why there’s an inconsistency in the Tahoe snowpack.

SNC senior Samir Somji grew up in British Columbia and has knowledge of snow science after spending 10 plus years in the backcountry guiding multiple touring expeditions. According to Somji, the location of Incline Village is between the Sierra Nevada and Carson ranges. The Carson Range is an inner-mountain snowpack, which is a desert environment. The snow is drier, fluffier, and lighter compared to the west shore, where it’s more dense and deep.

There is not a consistent snowpack in Lake Tahoe as the weather determined by the location and strength of two atmospheric systems- El Nino and La Nina. These act as a single large body of water moving back and forth as cold and warm phases between North America and Asia.

“There is no correlation between El Nino and La Nina in forecasting weather in Tahoe; there was no clear relationship,” Laguardia said. Over the past 10 years, meteorologists have shifted the way they determine weather forecasts from focusing on El Nino Southern Oscillation (ENSO) to atmospheric rivers.

There are variable patterns with weather that develop the inconsistency in the snowpack. In the U.S., there are three different snowpacks: maritime, inner mountain, and continental. According to Somji, “The continental snowpack is in Rocky Mountain range, the maritime snowpack is in the Sierra Nevada mountain range, and the inner mountain is everything in between. Maritime is deeper and denser. Continental is cold, shallow, and faceted snow. Inner mountain is drier and cold.

In predicting the recent storms, Laguardia explained, there is no sign of a persistent ridge after this storm passes; a little storm with a longer duration of ridge storms is approaching from the north, causing another weather system to move in. The term “ridge” is used to explain an elongated area of high pressure extending itself from a high-pressure region. Laguardia explained it is hard to predict weather three months out. Predictable big storms are usually atmospheric events. Forecasters can normally predict large storms within five to six days. If there is a large radar signal, they can predict storms six to eight days out.

More info: If Tahoe locals are interested in tracking weather, NOAA.com and Opensnow.com’s forecasts from Bryan Allegretto, are good places to start.