Tahoe Backcountry Snow

Blocked out

December 1st, 2024
0600 temp. at 6350′ in Carnelian Bay: 31.5 deg. w/ 98% RH

Backcountry obs:

Touring around the Mt. Rose backcountry on Thanksgiving Day (11/28) and Sat (11/30) revealed a drying snowpack that has largely remained cold, despite well above freezing temperatures the past few afternoons. A very dry airmass with RH (relative humidity) values in the single digits has kept protected areas above 8500′ cold and fluffy due to evaporative cooling. However, that very same dry air is pulling moisture out of the snow, thinning the dense cement that recently covered twigs, rocks, bushes. As a result, I sank deeper on my last tour, scraping some granite and stumps on my way down. It’s increasingly sharky out there!

Additionally, the excitement for early season turns, along with folks tromping around chopping down Christmas trees created tons of tracks of all varieties throughout the backcountry. Fresh, scratch-free turns are now a rare commodity and will become ever scarcer until a storm system finally brings more snow. And that may take some time.

Weather/forecast thoughts:

The Tahoe Sierra has been locked into strong high pressure and powerful daily inversions the past few days. High temps at lake level have struggled to break 40 deg., while along the peaks and ridge tops, highs have reached the mid-upper 40s. Low temps have been more dramatic with teens and 20s in the valleys while peaks remained in the 30s! Fog and low clouds have also developed in depressions overnight, leaving a coating of heavy frost and surface hoar that glistens with each sunrise.

The powerful ridge over the west will continue to block any storm system from arriving in Tahoe for at least the next week. Expect similar weather as we’ve had the past few days for the next week: cold nights, cool days under mainly sunny skies.

Looking out to the second week in December, models begin to show the possibility of some weakening in the current blocking pattern. Some small storms may affect the PacNW and drop into the Great Basin, just to our east, bringing cooler temps and little precip., if any, to Tahoe. It’s a ways out, but if these weak signals of change to the dominant blocking pattern were to play out, this would be a positive step towards moving the jet stream into a position more favorable for Sierra storms.

The snow will return at some point. Time to exercise patience.
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Winter appetizer

November 26th, 2024
0430 temp. at 6350′ in Carnelian Bay: 33.8 deg. w/ 92% RH

Trace new snow & 0.25″ rain in last 24 hrs.

0515 temp. at 8650′ Tamarack TH: 25 deg.

4-8″ observed new snow

Backcountry obs.:

Coverage in the Rose backcountry improved further with this last storm as another 4-8″ fell across the area in the last day. Predawn today (11/26) brought occasional snow showers, moderate to strong SW winds, and mostly cloudy skies. The new snow and strong winds wiped clean all leftover tracks from the weekend, leaving a soft, yet densely buffed, wind-textured surface from TH to summit. Near and above treeline firmer, wind-sculpted pillows and fins had begun to form downwind of trees and protruding rocks. The high water content in the snow and brisk winds throughout the storm are evident in the compacted nature of the snow. No blower pow to be found!

But while the snow might not be blower, it continues to plaster the backcountry forming a dense, solid base for the nascent season. It’s low tide, but the high density snow is keeping skiers from sinking into the depths where rocks, snags, and other sharks lurk, hungry to bite into new gear and tired legs.

The skiing this morning continued to outperform expectations. While thick and forgiving, the fresh snow provided springy, supportable pop in the trees and around features.

Forecast thoughts:

The storm of the past 24 hours left unremarkable, yet still welcome, amounts of new snow in the Tahoe backcountry. While it started out around daybreak on 11/25 with decent snowfall rates, temps by mid morning crested freezing below 7000′, turning precip to a rain/snow mix with little, if any accumulation around the lake. Areas from Carson Pass southward won this round.

Today will host a mix of clouds and sun with a few scattered snow showers, especially in the mountains. Any additional accumulations will be light. Moderate winds will continue throughout the day, grooming out the snow surface, before calming this evening as skies clear and temps drop. Backcountry zones will cool into the teens and low 20s overnight. Whatever snow falls today will have to suffice for quite a while…

Tomorrow sunshine returns while temps remain cool (30s in town, upper 20s on the mountains) as a ridge of high pressure moves into the region keeping skies clear. Temps will start to slowly moderate towards week’s end under generally fair skies and dry conditions. By the weekend, expect sunny skies and highs in the mid 40s around the lake, with 30s in the mountains. The dominant high pressure responsible for the clear weather could also set up strong inversions where lows in the Tahoe Basin and Martis Valley may be 10-20 deg colder than a few thousand feet up in the mountains. Hopefully the airmass will be dry enough that if temps do not cool below freezing, radiational cooling on the snowpack will keep snow soft and cold. The low sun angle of this time of year will also help to preserve snow, especially on NW-E aspects.

Model ensembles for next week and early December strongly favor calm, clear weather and mild temps as a blocking ridge of high pressure dominates the west. Signals indicating a breakdown of the ridge don’t yet appear in long term forecasts going out towards the middle of December.

Fill up now; it might be a while before winter serves up another course.
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Game on

November 25th, 2024
0530 temp. at 6350′ in Carnelian Bay: 30.2 deg. w/76% RH

Backcountry obs.:

And just like that, it’s game on for parts of the Tahoe backcountry. Last week’s storms, while disappointing around town, dropped between 1-2′ near the crest and in the Mt. Rose area. Along the W side of the lake, usable snow begins above 7000′ while the Mt. Rose area hosts snow above 8000′. Different from years passed, the snow that fell has a significant density, and arrived in a largely right-side up manner, with the densest snow at the bottom, getting lighter and fluffier towards the top. Despite being generally less than 3′ deep, the snowpack already buries many rocks, snags and smaller shrubs, spackling them in a supportable, springy, dense pack that doesn’t punch through. SW winds during the storm also distributed coverage well, filling in the nooks and crannies, especially in sheltered zones.

Be aware that the new snowpack does have multiple layers and density changes. Near and below treeline a ~2″ deep ribbon of loose, wet facets lies beneath a stout crust near the ground. I didn’t note any instability, but a sleeping bear may lurk beneath in the rights spots. Caution advised.

Top to bottom — taking good care towards the bottom — the skiing was fantastic this weekend with playful, bouncy powder, surprisingly few rock and log encounters and long, smooth turns. It’ll only get better from here.

Forecast thoughts:

After a bluebird break on Sun. (11/24), another potent storm system is approaching the Sierra beginning Mon. (11/25) and winding down Tues night (11/26). Like the previous systems, snow levels will generally float between 6000-7000′ during the bulk of precip, lowering as cooler air arrives towards the storm’s end. Accumulations at lake level will likely be meager. However, above 7000′ another 1-3′ could fall, especially for areas on the S and W sides of the basin. Points further S into Alpine and Mono Counties could receive even higher snow totals. It’s time for the Eastern Sierra to get their dose.

During the upcoming event, Tahoe will be sandwiched between two plumes of moisture: one dropping in from the N, and another arriving from the W, but aimed more directly at the Central Sierra. This more southerly–and more potent– plume will remain largely S of Tahoe, keeping the heaviest snowfall from Carson Pass southward. I wouldn’t be surprised if areas on the N side of Tahoe end up receiving forgettable accumulations that amount to less of a dump and more of a surface refresh.

Looking ahead to the coming week, Weds looks to clear out and remain seasonably cool as a transient ridge of high pressure moves in. A NW flow takes over for Thanksgiving into the end of the week providing the chance for some showers, but no significant storms beckon.
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Blocked out

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Winter appetizer

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Game on

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