Tag: weather

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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Game on

November 25th, 2024
0530 temp. at 6350′ in Carnelian Bay: 30.2 deg. w/76% RH

Backcountry obs.:

And just like that, it’s game on for parts of the Tahoe backcountry. Last week’s storms, while disappointing around town, dropped between 1-2′ near the crest and in the Mt. Rose area. Along the W side of the lake, usable snow begins above 7000′ while the Mt. Rose area hosts snow above 8000′. Different from years passed, the snow that fell has a significant density, and arrived in a largely right-side up manner, with the densest snow at the bottom, getting lighter and fluffier towards the top. Despite being generally less than 3′ deep, the snowpack already buries many rocks, snags and smaller shrubs, spackling them in a supportable, springy, dense pack that doesn’t punch through. SW winds during the storm also distributed coverage well, filling in the nooks and crannies, especially in sheltered zones.

Be aware that the new snowpack does have multiple layers and density changes. Near and below treeline a ~2″ deep ribbon of loose, wet facets lies beneath a stout crust near the ground. I didn’t note any instability, but a sleeping bear may lurk beneath in the rights spots. Caution advised.

Top to bottom — taking good care towards the bottom — the skiing was fantastic this weekend with playful, bouncy powder, surprisingly few rock and log encounters and long, smooth turns. It’ll only get better from here.

Forecast thoughts:

After a bluebird break on Sun. (11/24), another potent storm system is approaching the Sierra beginning Mon. (11/25) and winding down Tues night (11/26). Like the previous systems, snow levels will generally float between 6000-7000′ during the bulk of precip, lowering as cooler air arrives towards the storm’s end. Accumulations at lake level will likely be meager. However, above 7000′ another 1-3′ could fall, especially for areas on the S and W sides of the basin. Points further S into Alpine and Mono Counties could receive even higher snow totals. It’s time for the Eastern Sierra to get their dose.

During the upcoming event, Tahoe will be sandwiched between two plumes of moisture: one dropping in from the N, and another arriving from the W, but aimed more directly at the Central Sierra. This more southerly–and more potent– plume will remain largely S of Tahoe, keeping the heaviest snowfall from Carson Pass southward. I wouldn’t be surprised if areas on the N side of Tahoe end up receiving forgettable accumulations that amount to less of a dump and more of a surface refresh.

Looking ahead to the coming week, Weds looks to clear out and remain seasonably cool as a transient ridge of high pressure moves in. A NW flow takes over for Thanksgiving into the end of the week providing the chance for some showers, but no significant storms beckon.
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Tag: weather

Thick or thin crust?

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Blocked out

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Game on

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