Tahoe Backcountry Snow

0430 temp. at 6350′ in Carnelian Bay: 35.2 deg. with 98% RH

0515 temp. at 8400′ Incline Peak TH: 36 deg.

Backcountry obs.

Snow in the backcountry is now dominated by various crusts at all elevations and aspects. Expect combat skiing.

This morning a light refreeze on the snow surface made all crusts firm, but mainly breakable. Incline Peak is heavily tracked out and skin tracks are very icy. N facing aspects and sheltered trees tend to have thinner crusts with cold-ish snow beneath, while solar and wind exposed aspects have thicker crusts straddling the breakable/unbreakable line. Even the mellowest terrain has turned into adventure skiing.

Weather and forecast thoughts:

Today through Weds. will be warm and dry with partly cloudy skies. Highs around the lake will approach the lower 50’s, especially Sun. through Weds. while lows hang out in the mid-lower 30’s. Any refreezes on snow surfaces will be minimal. A dramatic shift to colder and wetter conditions takes hold Weds. PM into the weekend bringing snow (potentially significant) to all backcountry zones and elevations.

At dawn high clouds filled the skies with a grey film that has yet to clear by early afternoon. Moisture bumping up along the northwestern edge of the building ridge of high pressure is giving a “dirty ridge” feel to the warm, calm weather. Inversions are in place in the Tahoe Basin with temps. hanging in the low 40’s near lake level with upper 40’s to near 50 in the 7000-8000′ range. Periods of high clouds streaming aloft from now through Wednesday will help keep low temperatures high, adding to the slow bake of the snow pack over the next few days.

It’s a good time to tune up skis and boards for the second half of winter. The warm trend will be short-lived.

Starting Weds. PM, a shift to a more active and cooler pattern begins with the arrival of an initially warm storm (snow levels starting ~7500′) lowering down to lake level by the wee hours of Thurs. AM. Snow looks likely from Thurs., through at least the first half of the coming weekend.

Details of each system within the shift remain hazy this far out. Models continue to play with the idea of a splitting upper jet that favors the Sierra south of Tahoe for heaviest snowfall. In the past day, the idea of AR potential and a subtropical moisture plume phasing with the storm has also begun to look less likely. Despite the hints of these tempering forces conspiring to not wallop our area with multiple feet of snow, the pattern does look highly favorable to rounds of colder, wetter storms through at least next weekend. Looking beyond, ensembles show a strengthening subtropical jet into SoCal, which could bode well for our area being on the colder side of incoming Pacific storms.

Winter is far from over and there’s much reason to hope looking ahead into February.

0430 temp. at 6350′ in Carnelian Bay: 31.7 deg.

No new precip.

0515 temp. at 8650′ Tamarack TH: 32 deg.

No new precip.

Backcountry obs.:

Today dawned overcast and gloomy in the mountains with light to moderate NNE winds, especially along the ridge tops. A few flurries whizzed around my headlamp this morning, but nothing steady or heavy enough to accumulate.

Temps. are warm and the snow is responding. At dawn, cold snow was still abundant in the Rose backcountry from 8500′ upward, but it’s getting warmer and more dense. Surfaces are slightly wind-textured and soft in protected and shaded areas. Open aspects and even some N facing chutes have about an inch of higher density, yet easily turnable buff atop cold, soft snow. More exposed ridges feature sastrugi, wind plaster, and wind hardened sun crusts on solar aspects.

The skiing was forgiving, soft and fun this morning, but with quickly warming snow, it should expire by afternoon.

Weather and forecast thoughts:

Today begins the warm up, but with an unsettled and humid flavor to the change intially. Abundant cloud cover and temps into the mid 40’s are expected today as a system skirts by to the N. Tonight temps stay warm under cloudy skies.

Tomorrow will be even warmer with highs around the lake near 50 deg. under mostly cloudy skies with an outside chance of a light shower or sprinkle. Snow levels will remain above any mountains in our area.

Sun.-Tues. the ridge of high pressure responsible for the warmth will strengthen, clearing out skies and pushing temps. 10-15 deg. above average: low 50’s in lake and mountain communities, mid 40’s in the backcountry. Unless combat skiing heavy, wet mank, and crust is your thing, it might be a good time to hop on a bike or hit the beach. Corn snow seems unlikely with the current sun angle, duration of the warmup, and weak refreezes–if at all–during the thaw.

Fear not! Around the middle of the week, models agree on big changes that bring the Pacific jet right into our area, then sagging further south. This will bring storminess and colder temps.! AR (atmospheric river) prediction tools are also signaling decent chances for AR enhanced moisture to accompany the storms.

Specifics on the track and strength of the upcoming storms in the pattern change are still tough to nail down. Models evolve with each run and are not yet in complete agreement, especially on storm tracks. Some bring in a few storms into the Central Sierra, others start with Central Sierra hits, then a progression further S, favoring Mammoth to Southern California. Probabilistic forecasts do show a better than 50% chance for up to a foot of snow for the crest in the Tahoe Sierra.

It’s still too far out to build expectations on any amounts. However, expecting the incoming January thaw to be brief, followed by a solid refresh in the mountains is looking more and more like a good bet starting around the middle of next week.

0600 temp. at 6350′ in Carnelian Bay: 27.7 deg. & 88%RH

New snow: a dandruffing of flakes

No backcountry obs.

Backcountry obs.

No first hand obs. today. Remote sensors showed cold temps hanging on yesterday, which dropped further last night and this morning. Winds were moderate throughout the day yesterday, but sheltered areas probably still harbor cold, soft snow, even if heavily tracked out.

Reports of rain near 8500′ and higher came in along the crest yesterday. I suspect a rain crust coats the surface in zones on the W side of the lake.

Weather and forecast thoughts:

Last night another weak impulse came through the region from the N lowering temps and dropping the slightest accumulation. At the house, a pattern of large snowflakes coats the street. It looks as though a giant with an itchy scalp walked down the street, leaving a trail of flakes behind.

Today a light northerly flow will keep temps cool (upper 30’s around the lake) under mainly clear skies. It might just be enough to preserve cold snow up high for one last day. RH values may also dip providing an extra cooling agent on the surface snow. Tonight lows will dip again, refreezing whatever’s left on the ground at lake level and keeping snow up high cold and dry.

Tomorrow the Juneuary thaw begins in earnest until the next pattern change around the middle of next week. Temps. will get into the middle 40’s tomorrow, then rise into the lower 50’s Sat. through at least Tues., 1/30. Skies will be mainly clear, with occasional passing periods of cloudiness under what will initially be a “dirty ridge” of high pressure. A few stray liquid showers could sneak in on Sat. for most elevations. Snow levels will be near or above 9000′. Sun.-Tues. it will be warm and sunny. Low temps during the period may not even get down to freezing. Backcountry snow quality will suffer.

Details of the upcoming pattern change are still fuzzy as models continue to evolve with each run. A stormy pattern should return around Weds./Thurs. of next week, starting warm and cooling off with time. CPC (NOAA Climate Prediction Center) 8-10 day forecasts for the period show average temps and probabilities notably weighted towards above average precip. Recent models for late next week suggest colder storms splitting and/or favoring the central and southern Sierra. However, each model run shows something different this far out. Time will tell.