Tahoe Backcountry Snow

0800 temp. at 6350′ in Carnelian Bay: 32.4 deg. & 98% RH with light snow

24 hr. precip: .19″ rain / 1-2″ snow

0530 temp. at 8460′ Incline Peak TH: 30 deg. (falling) with light to moderate snow

2-5″ new snow accumulation as of 0700.

Backcountry obs.:

The much anticipated storm has under performed. Early this morning the changeover to snow did not happen at lake level until around 4:30. Since then, snow has been falling lightly with temps. in the low 30’s. With main band of precip. now to our south and breaking apart, it looks as though the bulk of today’s accumulation has passed. Lingering showers remain.

Precip. shadowing was very evident this morning in the backcountry as Incline Peak only had about 2″ at the TH and around 5″ near the summit at 9500′. During my tour, snow fell around 1/2″ per hour, but pulsed in and out. Winds blew out of the SW in the light/moderate range in open areas and on the summit.

The skiing has vastly improved, but still has a ways to go to recover the soft, bottomless goodness of a powdery mid-winter state. Concrete-hard ruts and tracks from the warm spell are still evident, yet fattened and softened with the new snow. A few more inches should erase them completely. For today expect a heavy dust on crust. The underlying firm surfaces are noticeable with most turns, and especially evident with slipage on steeper, side-hilling sections of the skintrack. The snow has not yet bonded to the crust beneath.

Instabilities noted were confined to loose sluffs running down steeper chutes and gullies, but nothing entraining larger cohesive slabs of snow. At the time of my tour there was not enough snow – except in deposition zones along the lee side of ridge tops – to pose any significant avy risk.

Weather and forecast thoughts:

Some years storms seem to get more potent with each model run in the days preceding their arrival. Then when they hit, they all overperform… That’s not 2024.

Today’s storm arrived late last night with rain at lake level until the predawn hours. An inch or so has fallen as of mid-morning, with Rose zone backcountry amounts in the 2-5″ range. A far cry from 1-2′.

Snow showers and cool temps. will prevail today with highs in the low-mid 30’s around the lake, with below freezing temps holding above 7000′. Snow levels will fall to around 5000-5500′ by afternoon. Expect a few peeks of sun in between snow showers, but otherwise skies will remain mostly cloudy. An additional inch or two can be expected in town with slightly greater amounts in the backcountry. Higher amounts will be along CA 89 and on the Crest.

Additional light snow showers will continue tonight and into tomorrow as the moist upsloping flow off the Pacific takes hold. Tomorrow a new, modest impulse swings through in the afternoon, increasing snowfall potential. Another few inches can be expected around the lake, with higher amounts in the mountains and along the crest. This refresh is coming in inch by inch.

Saturday and Sat. night some stray snow showers will grace the region under a mix of clouds and sun, with cooler temps. in the low 30’s during the day and 20’s at night.

The next potential big storm gets rolling on Sun. afternoon and looks to continue through Mon. evening/early Tues. Models this morning show a low developing off the coast that will phase a subtropical moisture fetch with cooler air, bringing another round of snow to the Sierra. Temps will remain cold enough for snow at all elevations – even down into W. Nevada valleys -for the duration of the event. The position of the low near the Monterey Bay is ideal for steering and forcing moisture up against the Sierra to be wrung out as heavy snow.

Probabilistic models this morning have Tahoe Basin communities with a greater than 50% chance of 12″+ and 2-3′ up along the crest. Models are also running a bit wetter today with higher QPF (quantitative precip. forecast) amounts than yesterday. With the storm still a few days out, details on timing and specifics have yet to crystalize and I expect multiple revisions on snow amounts over the next few days. This season has been marked with storms losing their punch as they hit the Sierra, so it’s difficult to see big projections and have confidence that they’ll hold.

That said, the show for this cycle is only getting started and conditions in the backcountry will improve over the next few days: inch by inch at first, then potentially with a big wallop.

0430 temp. at 6350’ in Carnelian Bay: 42 deg. & 50% RH

0515 temp. at 8650’ Tamarack TH: 34 deg.

Backcountry Obs.:

I got out this morning to see what the incoming snow will fall upon and as expected, crusts cover all elevations and aspects from 8600’-9000’ in the Rose backcountry. On windward and solar aspects, these firm surfaces are not even penetrable with the blunt end of a pole. In sheltered areas and NE aspects, crusts are generally 1/2-1” thick and semi supportable. Cold snow lays beneath.

Why does this matter? The crusts create a new bed layer upon which instabilities may form and run in future avalanche cycles. With the early season PWL (persistent weak layer) now less of a concern, most issues will occur from the current surface up.

The big question with the incoming storm today is how well the new snow bonds with the current surface snow. At this point, the storm looks to start warm and finish cold, which in general bodes well for bonding and stability.

The skiing today: hateful, survival combat. A week’s worth of traffic, complete with deep ruts, dinosaur tracks – and who knows, maybe even a mule train or two – on refrozen firm surfaces that occasionally give way, made for a tiring descent. Good thing a fresh start is inbound.

Weather and forecast thoughts:

Today dawned with moderate winds, foreboding skies, and warm temps. Winds ahead of the system have mixed out the inversions of the past few days, improving air quality, but also raising temps and lowering humidities. The storm is already appearing on radar over the North Coast and should begin impacting the Sierra late this afternoon/early evening. NWS Reno issued a Winter Storm Warning yesterday which still remains in effect from 10am today through 10am Fri. Expect a windy day today with increasing clouds, temps in the 40’s, and rain/snow moving into the area late in the day.

Precip. will begin falling as rain around the lake, quickly transitioning to snow and picking up in intensity late tonight through tomorrow morning. Snow levels still look on track to start around 7000′, then fall quickly through lake level and down into the 5500-6000′ range on Thurs. Updated model projections for the storm have trimmed down snow totals a bit for tonight-tomorrow evening to 12-18″ above 7000′, up to 6″ in mountain communities.

The angle of the storm up against the Sierra is a big factor in trimming the snow totals. As the storm hits the range, the flow will be shadowed, meaning more precip. will fall on the western slopes. The crest and areas along CA 89 will get the most, falling off considerably the further east you move.

Behind the opening salvo, a moist flow off the Pacific will promote snow showers continuing Thurs. PM, Fri, and into Sat. Some of these could be convective, giving them an extra punch with some snow bursts freshening up the mountains each day, especially during afternoon hours. A rumble of thunder isn’t out of the question along the crest either.

Looking at the next system, this morning some of the models suggest things getting going Sat. night and lasting into Tues. This one is giving strong signs of being a classic dump machine with the ability to deliver feet to the mountains and maybe even at the lake. There is plenty of cold air in place, so snow will fall at all elevations for Tahoe communities and backcountry zones.

This system is looking pretty complex as it combines a strong AR (atmospheric river) of subtropical moisture phasing with colder air as a closed low drops down the Pacific coast. The strong low will help provide dynamic lift to the moist air as it hits the Sierra, wringing out its contents as heavy snow.

I expect quite a few revisions to the forecast in the next few days. Closed lows are notorious for wobbling about as they travel due to being disconnected from the jet stream and larger upper flow. This makes predictability for specific impacts challenging. Any change in the track of the low a hundred miles one way or another, could significantly alter which parts of the Sierra receive the heaviest snowfall. It’s going to be fun to watch.

For now, snow moves in tonight giving the backcountry a welcome refresh. Never waste a powder day!

0600 temp. at 6350′ in Carnelian Bay: 34.2 deg. & 94% RH

No backcountry obs. today.

Weather and forecast thoughts:

Today is the last calm day before the next storm system begins impacting the region. Highs will be in the upper 40’s to low 50’s around the lake under a mix of clouds and sun. Tonight’s lows will again be in the low to mid 30’s under cloudy skies. Southerly breezes will start announcing the coming change later today and tonight, steadily gaining strength before maxing out with the storm’s arrival late tomorrow.

Models continue to show a strong AR approaching the coast tomorrow that marches across the state bringing a wallop of heavy precip. and high winds. Winds will peak by late Weds. before falling off behind the initial band of heavy precip. By the time the storm arrives into the Sierra, snow levels will start near 7000′, then crash over the evening on Weds., bringing snow to all backcountry zones in Tahoe. Snow levels should settle in the 5500′-6000′ range by Thurs. as snow continues falling throughout most of the day. The heaviest snowfall rates look to affect our area from the wee hours of Thurs. through Thurs. morning before snow turns more showery in nature on Thurs. afternoon.

By Thurs. night, storm totals above 7000′ could range anywhere from 1-2′ with locally higher amounts along the crest, while Tahoe communities can expect 6-12″.

Fear not, for this looks to be the opening salvo! Moist, unstable flow under a cold airmass will continue to bring snow showers to our area Fri. and Sat. A few inches of refresh each day seems likely.

Sun. through Tues. things get interesting. In the last day, the GFS has consistently shown another low developing off the CA coast that taps into a robust plume of subtropical moisture. In the models, this phases with the colder air to create a solid Sierra dump starting Sun. and lasting into Tues. At this point, this early week storm looks like it could be more potent than the system coming in tomorrow. It’s still 5 days out and details remain fuzzy, but the model trends and atmospheric ingredients are promising for getting a proper Sierra storm.

The dynamics in the atmosphere are highly conducive to winter storms affecting the Sierra over the next week to 10 days. Just for good measure, be sure to wash your car today before humbly tuning your sticks and rechecking avy safety gear. The weather gods have done a great job at neutering the winter this year, but in case they are feeling merciful, it’s never a bad idea to be ready.