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.