Tahoe Backcountry Snow

0330 wx at 6350′ in Carnelian Bay: 27.7 deg. / 23.4 deg. dew point / 88% RH / gusty SW winds / overcast skies / 1″ new snow / .94″ rain

0500 wx at 7450′ Rose backcountry TH: 23 deg / gusty SW winds / overcast and fog with light snow

Backcountry obs.:

Round three of this week’s storm cycle wraps up this afternoon (2/7), after leaving highly variable amounts of new snow in the backcountry. In the Rose zone above 7500′, anywhere from 6-20″ of new snow sits atop multiple feet deposited earlier this week. Amounts dramatically increase with elevation, especially above 8000′, as all three storms were warm with fluctuating snow lines, often teasing 8000’+.

Coverage is a non-issue above 8000′, but from 7500-8000′, expect lumps and protrusions in the snow surface harboring any number of core-gouging surprises. Luckily, the new snow is quite dense, providing a decent buffer between skis and sharky, buried obstacles beneath.

High S and SW winds pounded the mountains over the past day, creating large wind slabs in near and above treeline terrain on leeward NW-N-NE aspects. The new snow has an assortment of density layers as well, worth digging into and inspecting before committing to avy-prone slopes.

Despite the wind, layered new snow, and sad-looking snowpack at lake level, the skiing is actually great in the mountains. Sierra powder is skiing cold and fast, providing good buoyancy and a splendid canvass for etching elongated snow signatures at high speed, or tight, poppy wiggles down open faces.

Fear not; it’s good out there!

Weather and forecast thoughts:

The next few days (2/8-2/11) will be cold, tranquil, and sunny before more storms take aim on the Sierra around the middle of next week.

This afternoon, lingering snow showers and gusty SW winds will continue to sculpt the backcountry snow surface. Temps won’t get out of the 20s above 7000′, with values barely reaching the middle 30s at lake level. Lingering cloud cover may also help preserve any soft snow on solar aspects.

Skies clear, winds slacken, and temps plummet tonight. Lows should reach the single digits to lower teens across the Tahoe backcountry.

Sat. through Tues. (2/8-2/11) expect generally sunny skies, cool daytime highs and generally light winds. Highs will largely stay in the 20s to low 30s above 7000′, with lows dipping into the teens each night.

Models are in good agreement showing a robust system impacting the region next Weds. – Fri. (2/12 – 2/14). At this point, the system appears colder than this week’s round of warm ARs with a strong low setting up off the OR/WA coast. This setup typically brings colder dumps to the Sierra. However, it’s still quite early and much could change over the next few days. Each storm is unique; keep the faith.

For now, there’s a weekend of bluebird to enjoy.

0400 wx at 6350′ in Carnelian Bay: 22.6 deg. / 14.4 deg. dew point / 70% RH / Light winds / Clear skies / 3″ new snow on 2/4 / 1.75″ rain on 2/5

0500 wx at 8400 Mt. Rose backcountry TH: 12 deg. / Moderate SW winds / Mostly clear skies

Backcountry obs.:

Despite waking to a disappointing surprise of no new snow at lake level, the Rose backcountry above 8400′ did not disappoint. 1.5′ – 2.5′ of new, wind-smeared, dense snow now sits atop rain crusts from the 1/31 – 2/3 AR event.

The new storm snow has an upside-down structure with notable density changes throughout. Colder, less-consolidated snow rests just beneath the denser, wind-massaged surface. Breaking trail is fairly laborious with a semi-supportable upper layer, breaking into the softer snow underneath, especially in wind sheltered areas. Wind-exposed zones near treeline offer more supportable snow and easier travel.

Wind-exposed aspects (SE-S-W-NW), especially near and above treeline hold heavily wind-affected snow with large pillows, drifts and fins of dense, yet edgeable snow. Lee aspects are wind textured, yet soft and supportable, offering plentiful opportunities to carve wide, buttery turns.

Weather and forecast thoughts:

The battle between cold air from the Gulf of Alaska and the central Pacific’s plentiful subtropical moisture has set up the recent boom or bust weather of the past two storms. While some cooler air had phased into the Tues (2/4) storm dropping snow levels to near 6000′, especially at the onset, it couldn’t beat out the deep warmth associated with the subtropical AR. Snow levels rose yesterday around midday to nearly 8000′ by nightfall, and didn’t recover their starting position until precip. ended overnight.

Today (2/5) offers a reprieve from the AR cycles. Sunny skies and cool temps will dominate as highs remain below freezing in the backcountry above 7000′. Brisk SW winds will hang on throughout the day and increase towards nightfall, presaging the arrival of the next storm.

Tomorrow morning (2/6), snowfall should begin around daybreak for all elevations in Tahoe. The incoming moisture will arrive into the resident cold air mass bringing snow to all elevations throughout tomorrow morning. However, as the day progresses, more robust moisture from the subtropics will filter in, nudging up snow levels to 6500-7000′ during the afternoon and evening. At the same time, a deep, cold, unstable low off the Pac NW will descend along the coast, phasing colder air into the moisture plume. The tension between these two air masses will create another round of high winds and intense precip. late tomorrow into early Fri (2/6), while also crashing snow levels back below 6000′ in the wee hours of Fri. AM. The timing and placement of the cold low will determine just how quickly snow levels fall.

By Fri AM, another 1-2’+ of new snow is likely in the backcountry above 7000′, with isolated spots in the alpine, especially near the crest, receiving up to 3′. Below 7000′, 4-12″ of new snow looks like a safe bet, with higher amounts along the west shore of Tahoe.

Cold, unstable air behind the storm passage will promote scattered convective snow showers throughout the day on Friday, adding a few more decorative inches. Temps will remain cold, not warming beyond the 20s above 7000′.

Looking ahead, the weekend is shaping up to be sunny and cold: bluebird.

0400 wx at 6350′ in Carnelian Bay: 39.6 deg. /25 deg. dew point / 56% RH / overcast skies / 24hr. rainfall: .50″ / 2.76″ rainfall since Fri (1/31)

0515 wx. at 8650′ Mt. Rose backcountry TH: 29 deg. / SW winds ~ 10mph / overcast skies

Backcountry obs.:

The weekend storm produced, just not below 8000′. Snow levels started off around lake level on Fri (1/31), but rose above 9000′ on Sat. night (2/1) before settling around 8200′ for much of Sun. (2/2).

As a result, there’s little new accumulation below 8000′ in the Mt. Rose area, but the snow stacks up, especially at and above 8500′ where 1-2′ of new, ultra dense snow fell, recharging the snowpack. The new snow has been heavily groomed by strong winds creating a supportable, yet delightfully edgeable — and ripable — surface. 1-3″ of soft, unconsolidated surface snow exists in sheltered treed areas while a few isolated wind-exposed areas host a 1/4″ breakable rain crust.

The quantity and spackle-like quality of the snow has dramatically improved coverage and skier confidence. Gone are the days of fearing knee snapping snags and stumps lurking just beneath the surface. The tide has risen! Let the fast, fearless turns begin!

Forecast and weather thoughts:

While round 1 of the prolonged atmospheric river (AR) brought the warm and wet, and the next two waves look to bring equally intense precip. rates, but with the gift of progressively colder temps. Expect the next round of heavy snow to impact the backcountry Mon PM (2/3) into Weds AM (2/5). There will likely be a brief break Weds AM – Weds PM, before the coldest wave in the series brings heavy snow to all elevations in Tahoe starting overnight Weds/Thurs (2/5) and lasting through Fri AM (2/6).

By Fri evening, model ensembles show total snowfall amounts between 2-4′ above 7000′. Locally higher amounts are plausible near the crest and at higher elevations.

Today’s break in the rain and snow will quickly end this evening as a plume of AR moisture descends upon the central Sierra from the north. Snow levels will initially start around 6500′, then gradually rise up to or slightly above 7000′ by Tues morning. Rain and snow will fall in earnest on Tues as a surface low and powerful upper level jet accompany the moisture plume, providing strong atmospheric dynamics for enhanced precip. rates, especially along the crest. By Tues evening, colder air works into the system dropping snow levels down to lake level. As precip. winds down Weds AM, 1-3′ of new snow is likely above 7000′, while anywhere from 4-12″ could coat areas below 7000′. Lower elevation snow totals will be highly dependent upon how fast cold air phases into the storm.

The daylight hours of Weds (2/5) will provide a brief reprieve before the final — and coldest — round of the sequence arrives Weds evening. Models are in good agreement for another strong and dynamic system with a deeper source of cold air, creating heavy snow Weds PM through Fri AM (2/7).

It’s taken a while, but winter finally looks to be turning on.