Tahoe Backcountry Snow

0430 temp. at 6350′ in Carnelian Bay: 33.3 deg.

Trace new snow / .35″ rain in last 24 hrs.

0530 temp. at 8650′ Tamarack TH: 24 deg.

2-3″ new snow

Backcountry obs.

This morning dawned blustery and cooler with scattered flurries around the area, including at lake level. Only a skiff of new snow coated coated the roads in the predawn. Climbing up Mt. Rose Highway, high winds sent spin drifts airborne, aggressively depositing snow into the roadway and limiting visibility.

In the skin track, 2-3″ of new snow had fallen in more sheltered areas from TH to summit. Any area exposed to the strong WNW winds had been scoured down to the sun and rime crusts created during the warm weather between the 1/13 storm and last night’s disturbance. Soft, high density snow lay in sheltered leeward aspects and in the trees. Areas that did receive new snow wind deposits had a drummy, upside down feel with higher density windblown snow resting on top of lower density cold snow. In sheltered solar aspects, an inch thick, semi-supportable crust, covered lower density cold snow beneath.

The descent skied surprisingly well considering the wind and meager snow totals. Sheltered zones without crust were soft and fun, while more exposed areas featured a mix of crust and fresh wind deposits deep enough for soft turns, but not quite large enough for concerning wind slabs.

The next 36 hours should provide a brief lull in the wind and snow before the next round of systems arrives. Cool enough temps. should prevail to preserve the soft snow.

Weather and forecast thoughts:

Last night’s system dropped mainly rain at lake level before tapering off to a few flurries and a light dandruff coating by early this morning. Low clouds and showers continued to hug the west shore by mid morning today suggesting a continuation of the moist, orographic flow along the Sierra crest.

Clouds and showers will taper throughout the day today, giving way to breaks of sunshine and seasonal temps. with highs in the upper 30’s to lower 40’s around the lake. Tonight, tomorrow, and Friday a transient ridge of high pressure builds back into the area clearing skies and moderating temps. into the mid 40’s Thurs. and Fri. Highs should get near to just above freezing today and tomorrow in the backcountry between 8000-9000′.

Fri. afternoon, the high pressure moves out and the storm door swings back open as a strong zonal Pacific jet is set to bring a parade of systems to the area. Models continue to agree on multiple waves of precip. arriving from the eastern Pacific, each containing a decent subtropical moisture tap.

The first few waves Fri.-Sun. don’t look particularly potent by Sierra standards, but expect periods of rain and snow throughout the weekend. Snow levels will dance between 6500′-7500′, due to the warm subtropical moisture feed with little cold influence from the north. Snow levels will rise each day and fall at night. The wave arriving Mon.-Tues. looks to be the most potent, but still as warm as the waves before it.

Going into midweek and beyond, the GFS ensemble shows the stout Pacific jet stream retreating back to the west with a ridge of high pressure emerging over the west coast and building into the inner mountain west. This would likely usher in a period of warm and dry weather, hopefully not for too long. It’s midwinter and high time for a strong cycle of cold storms.

0600 temp. at 6350′ in Carnelian Bay: 27.1 deg. & 98% RH

No new snow

No backcountry obs. today

Forecast and weather thoughts:

Inversions are in place this morning with low clouds hanging over the north side of the Basin. Temps. mid slope in the mountains are nearly ten degrees warmer than at lake level, but dewpoints have dropped, likely keeping sheltered snow cold and soft through radiational cooling.

The next system arrives late in the day today. Winds will steadily increase out of the SW and mix out the inversions and fog by midday. High clouds will arrive with the winds, announcing the imminent arrival of more precip. This system is transient and doesn’t have a robust forcing mechanism, but it does have a tap on subtropical moisture. The result will be a warm event beginning this evening and lasting through tomorrow morning. Rain and snow will be heaviest W, dropping off significantly from W to E across the Sierra.

Because of the subtropical moisture tap, snow levels will start out between 8500-9000′ this evening, dropping to around 7000′ by storm’s end. By tomorrow morning, 3-6″ of heavy snow could coat the backcountry. Anywhere from .5″ to 1″ of rain is possible across the Tahoe Basin.

A warm break in the action comes in behind this next system with highs around lake level in the mid 40’s under a mix of clouds and sun.

Fri. pm the storm door opens yet again, with models in agreement showing rounds of rain/snow as a strong Pacific jet takes aim on our area. It still looks like next weekend and the first half of the following week may bring abundant rain and snow, but with snow levels bouncing up and down between 6500-7500′. These storms will all have a subtropical tap to their moisture and with no phasing of cold air from the Gulf of Alaska. We may be in store for a mid-winter rain event in the mid and lower elevations.

On the upside, days of Sierra cement pounding the higher backcountry will continue to fatten up the snowpack and may even overload whatever’s left of the persistent weak layer instabilities that lurk at the bottom of the snowpack. Then we’d just need a cold cycle to load some powder on top and boom: party time!

But back to reality, warm sloppiness is imminent. Do what you can with it.

0430 temp. at 6350′ in Carnelian Bay: 30.4 & 99% RH

No new snow

0530 temp. at 8400′ Incline Peak TH: 24 deg.

No new snow

Backcountry obs.:

When I came out of the backcountry yesterday, there was a mix of clouds and sun and high humidity. The snow at the TH had lost its cold feeling and water rivulets gushed down both sides of the road. With the cool temps. last night, I feared that warmth from yesterday had refrozen into crust on all aspects. I was wrong.

Skinning up Incline Peak I found a mix of breakable crust on any aspect that receives appreciable sunshine, and cold, dense Sierra cement in the trees and on all features facing NW-ENE. It’s still January and the sun angle is pretty low, so aspects receiving little to no sun can still stay cold and soft under the right conditions. If the airmass can dry out a bit over the next 24 hours, with cold overnights, N facing protected snow could still remain cold and crust free.

Incline Peak has been heavily skied, especially through the N. trees and NE side of the E. bowl. Good cold snow is still plentiful though in the right sheltered zones. Coverage continues to improve making for fun descents. Stability also looks to be improving, but the buried persistent weak layer is still out there, so conservative risk management remains prudent.

Forecast and weather thoughts:

The moist airmass left in the wake of Saturday’s storm was apparent this morning as low clouds, heavy hoar frost, and patchy fog adorned the Tahoe Basin. By mid morning, most low cloudiness and fog had burnt off giving way to a sunny, relatively warm day. Highs today are in the low 40’s around lake level. Tonight should cool off again and offer a repeat or close relative of this morning’s conditions as high pressure reigns.

Poor predictability and shifting model forecasts have plagued this winter and this week is no different. Looking to midweek and beyond, the trend towards warm and dry is changing to warm and unsettled.

Tues. will see the arrival of more clouds and rain/snow by Tues. night. Snow levels will initially start very high around 8500′, before falling after midnight and through Weds. am. Precip. will end Weds. am with fairly light storm totals. I wouldn’t expect any more than a few inches of wet snow, even along the crest, due to the warmth and high snow levels. This will be a mainly rain event for areas below 7000′.

The remainder of the work week will be warm and dry with high temps. in the low – mid 40’s around lake level. Sunny skies should prevail from Weds. pm though Fri. pm.

Fri. evening, things begin to shift once again as a train of storms takes aim on us from the Pacific starting next weekend and continuing deep into the following week. Models show these storms coming in on a strong Pacific jet traveling almost directly across the ocean from southern Japan. The mid-latitude placement of the jet will likely draw in milder Pacific moisture to keep each wave of storms fairly warm with snow levels near or above lake level.

This pattern shift is still quite a ways off, but at this point there’s no obvious cold signal interacting with the incoming, juicy subtropical jet, which trends towards a storm cycle of warm storms with higher snow levels. Time will tell as the work week wears on.