Tahoe Backcountry Snow

0430 wx. at 6350′ in Carnelian Bay: 25.9 deg. / 19.6 deg. dew point / 77% RH / calm winds and clear skies

0530 wx. at 8650′ Mt. Rose TH: 20 deg. / calm winds / clear skies

0630 wx. at 9900′ in Mt. Rose backcountry: 24.0 deg. / 11.6 deg. dew point / NE winds at 5mph / high broken overcast skies

Backcountry obs.:

The Mt. Rose backcountry hosted cold, powdery surface snow this morning (2/21) with 2-4″ of light, low density snow atop a springy base. Temps in the low to mid 20s and moderate NE winds throughout the day yesterday (2/20) kept snow surfaces frozen, despite mostly sunny skies. Sun crust was limited to aspects receiving the most intense solar exposure during the day yesterday (SE-S-SW).

Near and above treeline, N and NE aspects showed little wind effect, skiing fast, soft, and super fun. Whoops and giggles from surprised skiers crackled through the early morning silence, signaling yet another sneaker pow morning.

Weather and forecast thoughts:

Not much change to the forecast from yesterday. Starting today, a warmup overtakes the region lasting through the end of February, bringing the season’s first substantial corn skiing window.

Highs in the backcountry will warm into the 40s this weekend under mostly sunny skies. Lows this weekend will be in the upper 20s and 30s above 8000′, providing generally good overnight refreezes. Sunday (2/23) increased breezes and high clouds will signal the passage of a weak system to our north. A few light showers are possible Sun. evening into early Mon. Snow levels for any precip. that does fall will be above 8000′.

The coming work week will be dry and mild with highs in the 40s above 8000′ and lows in the upper 20s to lower 30s. Snow surfaces should receive decent overnight refreezes through radiational cooling. This should set the stage for a prolonged window of early spring corn.

Models suggest modest, colder systems entering the picture around the ides of March continuing into the first full week of the month. Winter’s not over yet.

0700 wx. at 6350′ in Carnelian Bay: 22.8 deg. / 21.0 deg. dew point /93% RH. / Clear skies / 1″ new snow overnight

Backcountry obs., Eastside edition:

I spent the past weekend (2/14-2/17) in the Eastern Sierra checking out the newly refreshed snowpack near Convict Lake, Rock Creek, and Lee Vining. While there is now a useable snowpack in all three areas for the first time this season, signs of active instability were widespread, limiting access to low consequence terrain. Across the region, the recent storm dropped anywhere from 2-4′ of new snow above 7500′. In areas below 8000′, much of this fell on bare ground, sage and shrubs, and in some areas, faceted snow. Highest storm totals were from Mammoth north, with amounts tapering to the south. The storm snow exhibited an upside down character with multiple inches of lighter density snow, beneath a foot or more of denser snow near the surface.

Skinning near Convict Lake, the snow had a trampoline-like feel underfoot, with the denser surface snow bonded together atop cold, unconsolidated snow intermixed with shrub branches beneath. Near and above treeline, wind slabs felt drummy and hollow. On larger bowls, chutes, and prime avalanche terrain, evidence of recent large avalanches abounded. Numerous N and E facing chutes and bowls were dotted with visible crowns up high, and debris piles at their bases.

Adding to the awkward and unsettled feel of the snowpack was warmth. By 2:30pm on Sat., temps. climbed to 32.9 deg. at 10,780′ on Mt. Aggie. Snow quickly warmed and what had just been fluffy powder, quickly turned to hot pow and mashed potatoes. Increasing afternoon breezes refroze the snow surface in open areas so that a new, stiff and breakable crust now topped the newly heated, mashed potatoes underneath: mama’s secret recipe.

Saturday’s warmup was region-wide so that by Sun am, all but the most sheltered N and NE aspects in Rock Creek above 9000′ hosted 1″ thick melt-freeze crust atop 2-3′ of warming soft snow. Trail breaking was strenuous with deep ski penetration and constant skin glopping. Surprisingly, by mid afternoon the snow had warmed enough to weaken the previously breakable crusts. The skiing ended up being far more fun and enjoyable, especially down low, than anticipated. A few thousand feet of fun and giggly hot-pow replaced earlier fears of an afternoon combating death crust.

Late Sun and Mon (2/26-17), more changes arrived as a system to the north increased winds dramatically over the higher peaks, sending plumes and banners of fresh snow skyward and onto leeward slopes. On Mon (2/17) fresh wind slab avalanche debris littered the bases of bowls and couloirs in the alpine above Lee Vining. Touring on sheltered N and NE aspects of Mt. Dana, revealed surfaces of thick melt-freeze crust atop upside-down hot pow. Above treeline, wind sculpted sastrugi, edgeable windboard, breakable crust, and powerful SW winds all conspired to turn casual touring into a heads up adventure.

The Eastside now has a snowpack, it just needs time to settle and stabilize. With luck, a few more dumps in the next month will add more depth and set the stage for the sunny, good timing days of High Sierra spring.

Weather and forecast thoughts:

Speaking of spring, aside from the weak system affecting the area yesterday, warmth, sunshine, and high pressure will be the themes for the next week and beyond heading into March. Goodbye winter powder, hello spring corn.

The recent warmth earlier this week (2/17-2/19) that largely cooked the backcountry snowpack, departed late yesterday (2/19) with a weak storm, leaving a dusting of snow atop freshly frozen crusts. Today highs will remain cool in the lower 30s above 7000′ under sunny skies with some light N and NE breezes.

Starting on Fri (2/21) through the weekend and into next week, temps in the backcountry will warm into the 40s each afternoon under mainly sunny skies. Some passing storms in the Pac NW may bring periods of high clouds on Sun (2/23). However, that won’t keep temps. from rising each afternoon into the middle and upper 40s. Some locations could even flirt with 50 degrees early next week.

Nights for the coming period will be generally clear, permitting efficient radiative cooling of the snowpack. Lows in the backcountry will fall to the 20s and low 30s in a drier airmass, promoting additional cooling of snow surfaces. Nightly inversions are likely as well.

The coming combination of warm, sunny days and cold clear nights should combine to produce the first good corn cycle of the season this weekend through the end of the month.

Will winter return? Model ensembles suggest a pattern change back to unsettled weather possible around the first week in March.