Tahoe Backcountry Snow

Variable snow with warm and showery pattern on the way

December 20th, 2024
0400 temp. at 6350′ in Carnelian Bay: 31.1 deg. w/ 99% RH

0515 temp. at 8650′ in Mt. Rose backcountry: 39 deg.

Backcountry obs:

Above 8500′, the Mt. Rose backcountry is a mix of breakable crust and old, warm powder, heavily tracked out.

Temps on the Slide Mt. sensor have held well above freezing for the past few days (30s to low 40s), yet with low humidity. I got out this morning to see how things are holding up through the warm spell and whether any cold snow is hanging on. It is, if only in pockets.

From the TH, there is still soft snow in tree shadows and in shaded, N and NE aspects. However, anywhere that receives sun exposure, even at the winter solstice, has a healthy, breakable crust. Higher up near and above treeline, N facing zones now host edgeable wind pillows along ridges and exposed faces, especially on spines and convexities.

Coverage remains at low tide, but is still good. Most rocks and branches are covered, but a few sharks and bare dirt spots still remain, especially in areas prone to channeling wind.

The variable conditions make for good training, and that’s how the backcountry skied this morning. Edgeable windboard, thick pow, and breakable crust demanded attention from mind and body. Moments of soft turning bliss could quickly turn into spicy crust management, then back to sneaky pow all within a few turns. Conditions aren’t great, but they’re still worthwhile and fun.

Weather/forecast thoughts:

Today should be the last day of stagnant air, low clouds, and inversions for the lower elevations as a series of storms begins affecting the region late tonight and into tomorrow (12/21) with high winds and showers. The unsettled pattern will take effect tomorrow and last through Christmas week as a procession of mild AR-fueled storms impacts the Tahoe Sierra.

The first system in the series will have its aim on southern Oregon and extreme northern CA. As such, Tahoe will remain on the warmer side of the storm with occasional showers around the lake and higher elevation intermittent snow starting between 7000-8000′. Accumulating snow will be confined to higher zones above 8000′ with only a few dense inches expected. The greatest impact from the Sat system will likely be high SW winds that could gust well in excess of hurricane force (75mph +) along ridgelines late Fri night and Sat.

Temps in the backcountry will be in the low to mid 30s on Sat with lows in the 20s and 30s. on Sat night. Around town expect low 40s on Sat with lows only at or just above freezing by Sun morning.

Spotty showers could linger Sun and into Mon with warm temps and high snow levels making for soppy snow below under a mix of clouds and sun. Highs will be in the upper 30s to mid 40s with lows in the upper 20s to mid 30s.

The next significant system looks to arrive on Christmas Eve. Models have been trimming precip. amounts back over the past day, but a moderate storm can still be expected Mon night – Christmas morning (12/23-12/25). The system will have a good fetch of subtropical moisture starting warm and ending cool. Snow levels around 8500-9000′ at the onset will drop throughout the day on Christmas Eve before bottoming out below 6000′ in the wee hours of Christmas morning as precip ends. A fresh white Christmas looks like a decent bet with maybe 1’+ above 8000′, while lower elevations could receive a few festive inches.

Beyond Christmas, models suggest that mild storms could keep rolling in.
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Another snowfall surprise and a warmup

December 17th, 2024
0400 temp. at 6350′ in Carnelian Bay: 30.1 deg.

New 24 hr. snow: 5.5″

0515 temp. at 8650′ Tamarack TH: 28 deg.

New 24 hr. snow: 6-8″

Backcountry obs:

Yesterday’s storm surprised yet again with higher snow totals around the northern side of the lake, while points south picked up a slushy inch. Warm, moist air moved into with the system around mid-morning bringing snow levels up to around 8000′ by afternoon, even in spots that initially picked up more snow than expected. By noon, moderate rain soaked backcountry zones around Mt. Tallac, Emerald Bay, and the West Shore. This morning, rain crust reports abounded in much of the backcountry below 8000′.

The one zone that survived the warmth: Mt. Rose. Temps during the storm never crested freezing, resulting in another 6-8″ of thick cement, resetting the snow surface and providing fun, thick hero pow.

The combination of high water content snow and strong winds during the storm has created abundant wind board along ridgelines and in exposed areas. While not escaping the wind entirely, W-N-E aspects skied well at dawn on wind affected, thick buff, turning to lightly textured thick pow in the trees. Add a little extra pop to each turn for best results.

Weather and forecast thoughts:

Calm weather and warm temps will dominate the rest of the workweek both around town and in the backcountry. Expect morning fog and inversions in valleys and depressions with lows around freezing, or just below.

Daytime highs will hit the low 50s around the lake Weds – Fri, while backcountry areas reach the upper 30s above 8000′, to 40s below 8000′. Summits and ridgetops may not drop below freezing at night, but lower dew points and RH may preserve whatever cold snow that didn’t get soaked through evaporative cooling.

A stormy, active pattern is in the cards for the weekend, then continuing into Christmas week. The first storm takes aim on Tahoe for Sat and Sun (12/21 – 12/22). This one looks to have a warm, atmospheric river component, possibly driving snow levels all the way up to 9000′ and soaking the snowpack for all areas. Luckily the past few storms have laid down feet of thick cement that should handle a short-lived period of rain and warmth.

After a break in the action late Sun – Mon, models are in fair agreement that another storm will roll in for Christmas Eve / Christmas Day, this time bringing the gift of colder air and lower snow levels. Hopefully the fluffy fun returns just in time for the holiday.
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‘Twas a good storm; now some warmth

December 16th, 2024
0530 temp. at 6350′ in Carnelian Bay: 33.3 deg. w/90% RH

New snow in past 24 hrs: trace

12/13-12/14 total snowfall at 6350′ in Carnelian Bay: 17″

Backcountry obs:

The Fri / Sat (12/13-14) storm really over delivered dropping nearly a foot and a half on the north shore and up to 2-3′ for areas along the crest. Snow fell consistently throughout the event, with hours-long periods of heavy snowfall. Strong winds accompanied the storm, creating wind sculpted surfaces, even in sheltered zones below treeline.

Rain never came to lake level on Sat as temps hovered at or just below freezing through the warmest part of the storm. This translated to far higher snow totals than expected. And while the storm remained cold, the snow that fell was heavy, dense Sierra cement that the high winds distributed around nooks and crannies. Coverage has vastly improved down to 7000′, putting zones previously too bony to open up and lay into turns, now into play.

Touring in the Rose zone on 12/15 revealed at least 2′ of new, wind-affected snow with a few density changes throughout the new snow column. By dawn, winds had slackened and shifted to the NW, creating some turnable, yet fun wind buff near ridgetops and on open bowls. On E aspects, a few reactive wind slabs failed with ski cuts, yet did not extend beyond a few feet off the ridgeline. Interestingly enough, I didn’t observe any natural avalanches from the storm, despite the windspread faceted snow from late last week. Have the weaknesses healed or does the white dragon lurk below? Time will tell.

Weather and forecast thoughts:

Today (12/16) a quick, weak storm will swing through Tahoe during the daylight hours, starting as snow for most areas and finishing with a rain/snow mix around the lake. Snow levels should climb to around 7000′ before precip moves out in the early evening. Expect a dense 2-6″ above 7000′ with negligible slush to liquid amounts around the lake. Highs will be in the upper 30s, with lower 30s in the backcountry. Tonight will bring lows in the 20s on the mountains and temps near or just below freezing around 6000′.

Milder air and calm conditions return for the rest of the week with mainly sunny skies and highs in the mid-upper 40s, lows in the lower 30s around the lake. Inversions may develop again at night bringing low clouds and freezing fog to valleys and depressions. This regime will be mild for the backcountry as well with highs above freezing and lows just at or below freezing. The drier airmass and weak Dec. sun will likely keep snow surfaces soft and frozen on cooler, shady aspects.

Models indicate the return to an active pattern starting next weekend with a warm system possibly affecting Tahoe on Saturday and maybe something a bit colder and more robust around Christmas.
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Variable snow with warm and showery pattern on the way

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Another snowfall surprise and a warmup

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‘Twas a good storm; now some warmth

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