Tahoe Backcountry Snow

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.

0430 temp. at 6350′ in Carnelian Bay: 32.7 deg.

No new precip.

0515 temp. at 8650′ Tamarack TH: 28 deg.

Trace new snow

Backcountry Obs.

Low clouds, fog, and occasional rain/snow showers have started out the morning. At dawn in the Tamarack backcountry it snowed lightly and intermittently, accompanied by moderate winds out of the WNW.

Snow is still soft, holding up best on true N-NE aspects and in W-E facing trees. Yesterday’s fluffy, fast snow topped with surface hoar has morphed into thicker and lightly wind-effected 4-5″ of cold, soft snow, excellent for skiing fast and hopping around the forest. Lower on the mountain and on more southerly aspects, crunchy, refrozen tree melt has fallen and refrozen atop the snow surface in forested areas. True S aspects host a thin, breakable suncrust that is apparent, but not too widespread or bothersome to manage.

Moderate winds are lightly grooming the snow surface, but plenty of tracks remain visible. Apart from some subtle texture, especially near and above treeline, wind effect has been minimal at degrading the snow surface. Snow is available to transport, but pillows and wind slabs are not yet prominent, nor were actively growing on my tour.

The next system is quickly approaching and its warm moisture source is apparent. Fog enshrouded the summit this am and the snow feels as though it’s soaking up the moisture, becoming a bit more dense with windward areas riming ever so slightly.

Weather and forecast thoughts:

Today’s warmish system peaks later today with heaviest precip. along the crest and in the higher terrain. Any snow showers this morning will turn to rain in Tahoe communities as snow levels scramble back up to 7500-8000′. I suspect that with the warmth of this storm, another layer of warm fog or drizzle may affect the crest, yet again forming a rain crust higher than the forecast snow lines.

Highs today at lake level will be near 40, with temps. wobbling in the low to mid 30’s above 8000′. Tonight the system begins to ease and move out as snow levels drop once again, just in time for any residual showers to finish off the event with a cold dusting. Snow totals will likely end in the 1-6″ range.

Tomorrow the sun returns with seasonal highs near 40 at lake level, low to mid 30’s in the mountains.

Friday and Saturday begin the January thaw that envelops the region through the end of the month. Some showers could sneak in on Fri. and Sat. as Tahoe gets caught between a nascent ridge of high pressure to the east, and the moist southerly flow directed at the PacNW. Snow levels will be very high: up to 9000′.

The ridge amplifies even further Sun. through the middle of next week with highs around the lake in the low 50’s under generally fair skies.

Models and ensembles show an E. Pacific troughing pattern setting up around Feb. 1 with storms again entering the picture. The Pacific jet also looks to extend across the ocean towards the west coast. There’s little agreement today on specifics this far out, and just about any flavor of unsettled weather could befall the area. What does seem likely is an abrupt end to the warm and dry weather of the coming days.