Month: December 2024

Modest improvement on the way

December 11th, 2024
0400 temp. at 6350′ in Carnelian Bay: 31.4 deg. w/ 52% RH

0500 temp. at 8650′ Tamarack TH: 30 deg.

Backcounty Obs.:

I got out this morning on a quick tour to check the state of the Rose backcountry snowpack after a few weeks of mild, dry weather. Overall, the snowpack continues to hold its coverage and ski-ability above 8500′. Snow in the area is heavily tracked and worn. Most surfaces that receive any appreciable sunlight are coated in a supportable, combat crust. Cold, sheltered areas below treeline a mix of thin crusts and soft, cold, recycled pow, aka. facets. While soft snow exists, fresh tracks are rare.

Near and above treeline, recent N and NE winds have created some variable, cold windboard on and near ridges high in N-E facing terrain. Further down slope, the snow surface returns to soft, cold recycled pow. Digging handpits and probing these areas show that the snowpack now consists largely of faceted snow with little cohesion. It skis nicely now, but could become problematic once covered in higher density new snow.

Of note the past few days has been the dryness of the airmass. Dew points this morning on Slide Mountain were in the -20 deg range, translating to single digit RH levels. Yesterday and Mon. (12/9) were similar. This dry air is sublimating moisture out of the snowpack and cooling snow grains as it does so. This creates the poorly bonding recycled pow that’s fun to ski now, but will likely create avalanche problems in the near future.

Weather and forecast thoughts:

The storm door is finally reopening after weeks of patiently waiting as a modest storm begins impacting the Tahoe area late tonight (12/11). Snow should begin falling after midnight and will continue into most of tomorrow for all backcountry areas – and even in town around the lake. Local communities should pick up 2-5″ by Fri AM, with greater amounts N and W. Backcountry zones above 7000′ have a decent shot of receiving 4-8″ of refresh on the currently haggard, backcountry.

Temps. will remain cool throughout the event with highs tomorrow (12/12) wobbling around the lower to mid 30s in town, with 20s in the mountains. Snow levels look to remain below lake level for the entire storm.

Cool conditions and snow showers with little additional accumulation will linger about on Fri before the next storm moves into the area late Fri night into Sat.

Models are in fairly consistent agreement that the weekend storm should begin early Sat morning and increase in intensity throughout the day. Snow levels will begin near or above lake level (6500-7000′) on Fri night / early Sat, and fall throughout the day on Sat as cold air moves in on the back side of the system. Scattered showers with lighter accumulations will finish out the storm Sat PM and Sun.

As is typical, the highest snow totals will be west and north around the Tahoe Basin, favoring the crest. Backcountry areas have decent odds of picking up 12-14″ of new snow, while communities around 6000′ will likely see only a few slushy inches. Warmer temps and a more robust moisture tap will produce higher density snow, slightly moderating the low tide backcountry conditions, albeit atop a base of cold, loose facets. The adage, “today’s snow surface is tomorrow’s weak layer”, could prove particularly insightful in the coming days.

Looking ahead to next week, another cold, modest storm could be in the cards for the Mon-Tues time frame bringing another few inches of refresh for all elevations.

Weeks of patience might just be about to pay off.
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Thick or thin crust?

December 5th, 2024
0430 temp. at 6350′ in Carnelian Bay: 30.8 deg w/98% RH

0500 temp. at 8650′ Tamarack Peak TH: 22 deg.

Backcountry obs:

How do you like your crust: thick or thin? Crust is largely the only surface on offer in the Rose area backcountry as of this morning (12/5). The multitude of refrozen tracks, pine litter, and the occasional frozen dog turd really have the area looking haggard. Coverage is holding on, but some thin, wind-exposed zones near tree line are beginning to burn out down to bare rock and scree.

Near and above treeline, N-NE aspects hold cold, dry snow. Hanging depressions and sheltered areas in the trees did host widespread surface hoar atop 2-3′ of soft, old snow. Digging handpits in this area doesn’t reveal clear density changes in the snowpack, rather a fairly consistent pack of dry, degrading snow grains that adhere poorly, if at all to one another. Look out for these potential stability issues for the next snow event.

While it’s always nice to get out on a predawn tour, navigating crust and thin coverage made skiing tenuous at best, to full on combat in some zones. Not recommended for pleasure unless masochistic training is your thing.

Weather and forecast thoughts:

One thing’s for sure: the best turns of the season are yet to come. The stagnant, dry pattern locked in over Tahoe looks to continue with some minor changes over at least the next week. By mid-month, models hint at storms returning to area. The flavor and intensity of these future systems remains unclear as models change with each successive run. What does look promising, however, is a consistent signal in ensemble forecasts for change in the overall pattern favoring more active weather.

For the near term, expect mostly clear skies with highs in the 40s and lows in the 20s in valleys and depressions, near freezing temps along mid-slope areas, peaks and ridgelines: classic inversion weather.

A system will arrive into the PacNW Sat/Sun, then dive south and east into the Great Basin and western slope of the Rockies for early next week. Tahoe will see nothing more than cooler temps and increased NW winds late this weekend into early next week. This might help clear out the stagnant, smoky air plaguing area valleys.

Ridging and high pressure return for the middle/end of next week (12/10-12/13) with sunny skies, cool days and cold nights, much like this week.

Models and their ensembles do show changes to the pattern starting next weekend (12/14-12/15) with the ridge breaking down and storms potentially returning to the area.

Winter is bound to return, it’s just a question of when.
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Blocked out

December 1st, 2024
0600 temp. at 6350′ in Carnelian Bay: 31.5 deg. w/ 98% RH

Backcountry obs:

Touring around the Mt. Rose backcountry on Thanksgiving Day (11/28) and Sat (11/30) revealed a drying snowpack that has largely remained cold, despite well above freezing temperatures the past few afternoons. A very dry airmass with RH (relative humidity) values in the single digits has kept protected areas above 8500′ cold and fluffy due to evaporative cooling. However, that very same dry air is pulling moisture out of the snow, thinning the dense cement that recently covered twigs, rocks, bushes. As a result, I sank deeper on my last tour, scraping some granite and stumps on my way down. It’s increasingly sharky out there!

Additionally, the excitement for early season turns, along with folks tromping around chopping down Christmas trees created tons of tracks of all varieties throughout the backcountry. Fresh, scratch-free turns are now a rare commodity and will become ever scarcer until a storm system finally brings more snow. And that may take some time.

Weather/forecast thoughts:

The Tahoe Sierra has been locked into strong high pressure and powerful daily inversions the past few days. High temps at lake level have struggled to break 40 deg., while along the peaks and ridge tops, highs have reached the mid-upper 40s. Low temps have been more dramatic with teens and 20s in the valleys while peaks remained in the 30s! Fog and low clouds have also developed in depressions overnight, leaving a coating of heavy frost and surface hoar that glistens with each sunrise.

The powerful ridge over the west will continue to block any storm system from arriving in Tahoe for at least the next week. Expect similar weather as we’ve had the past few days for the next week: cold nights, cool days under mainly sunny skies.

Looking out to the second week in December, models begin to show the possibility of some weakening in the current blocking pattern. Some small storms may affect the PacNW and drop into the Great Basin, just to our east, bringing cooler temps and little precip., if any, to Tahoe. It’s a ways out, but if these weak signals of change to the dominant blocking pattern were to play out, this would be a positive step towards moving the jet stream into a position more favorable for Sierra storms.

The snow will return at some point. Time to exercise patience.
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Month: December 2024

Modest improvement on the way

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Thick or thin crust?

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Blocked out

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