Tahoe Backcountry Snow

Backcountry obs.:

0515 wx. at 8650′ Mt. Rose TH: 32°F / rain/snow mix / new snow: ~14″

0639 wx. at 9800′: 29.1°F / gusty SW winds between 10-15 mph / new snow: 24″+

Snow has finally arrived to the highest reaches of the Tahoe backcountry. A morning tour today (12/22) in the Mt. Rose backcountry between 8650′ – 9800′ revealed a changed landscape with 14″ of dense, wet cake batter snow at 8600′, while 24″+ now coats areas above 9100′. Gone are the wet rocks, stumps and shrubs, replaced by feet of solid, dense base. This is just what the doctor ordered. 

While far from powdery, the new snowpack trades fluffy turns for the security of knowing that a sharp rock or snag is less likely to jump out and eat your legs while laying down a flowy turn. Throughout the tour snow felt right-side up with no obvious instabilities. The uppermost elevations skied surprisingly fast and smooth: a springy cream cheese base coated with cold and zippy powdered sugar on top. Even down low there was little evidence of the warm rain/snow I encountered at the beginning of my tour as colder temps and dropping snow levels had already re-firmed and coated the snow surface upon descent. A real holiday treat!

Weather and forecast thoughts:

The grueling wait for winter is finally ending. Beginning Christmas Eve, multiple rounds of intense snowfall will pound the Tahoe Sierra through Christmas day and through most of Friday (12/26). By dawn on Sat (12/27), guidance suggests that multiple feet (3-5′) of heavy, dense snow will coat the backcountry above 7000′, with 1-2′ of new snow at lake level. The weekend and beginning of next week look quieter with near normal temps (30s at lake level, 20s and low 30s above 7000′).

Today (12/22) snow levels dropped to near lake level during the heaviest precip, but accumulations remained above 8000′ except along the northern shoreline of the lake. This evening showers will diminish from south to north, giving way to a break in the action tomorrow (12/23). Temps tonight will remain steady, then begin creeping upward with the southerly flow ahead of the next system.

Tomorrow (12/23) looks quite a bit calmer than the past few days with partly cloudy skies and the chance of a stray shower passing through. Snow levels will remain elevated, climbing back between 8000-8500’.

The main event looks to arrive in the wee hours of Christmas Eve morning. The storm will start warm with snow levels between 7500-8000′, which start falling around daybreak. Rain and snow will continue through the day changing to all snow by lake level late in the afternoon. Significant accumulations will likely be confined to areas above 7000′ on Christmas Eve.

Once snow levels drop on Christmas Eve, they’ll stay around or below lake level through Christmas, falling even further on Friday (12/26), increasing snow ratios and boosting total amounts. A series of short waves will rotate into the Sierra around a low off the coast near the CA/OR border phasing progressively colder air into a deep moisture fetch creating a setup for heavy Sierra snow lasting through most of Friday (12/26).

Total amounts are still in question with the current spread in the models, but in the past day they’ve begun coming closer together.

Either way you slice it, snow totals will be measured in feet. A right proper Christmas dump.

Once skies clear on Saturday, expect cool temps and sunshine for the weekend and beginning of next week. More storms could return just after the New Year.

The wait’s officially over. Backcountry ski season is here.

Backcountry obs:

0545 Wx. at 8750′ in the Mt. Rose backcountry: 37.1°F / dew point: 7.4°F / RH: 30.3°F / calm winds / snow depth: 0-12″ depending on aspect

A tour of the Rose bc around dawn on 12/15 revealed a nearly unusable snowpack below 9000′ on all but the most northerly, shaded aspects. It’s grim, bottom of the barrel skiing out there. Above 9000′ coverage improves, but it’s very low tide after nearly 4 weeks of warm, dry weather atop a thin, early season snowpack. Surface conditions are highly variable and very skied out in popular zones. The most southerly, solar aspects at high elevations present some “baby corn” melt freeze surfaces, while mixed shade areas host breakable crust atop nearly 8-10” of loose, dry facets. True northerly, sheltered zones have soft, crust free, faceted snow down to the October storm interface.

Aside of the nearly unskiable nature of the current snowpack, the abundance of loose, faceted snow beneath surface crusts and across northerly aspects raises the alarm for future deep instabilities once snow does arrive.

Weather and forecast thoughts:

A pattern change heralding the end of steep inversions and warm, sunny days across the upper elevations is upon us. This week, rounds of very moist systems will begin impacting the Tahoe Sierra starting today (12/16) through Weds (12/17), and again late Fri (12/19) through the weekend into next week. The parade will continue on and off through at least Christmas, and likely beyond.

While current guidance favors high precip. amounts throughout the period, above average temperatures and stubborn warmth will likely plague each system into early next week. High snow levels, especially with the first two systems, will keep snow confined to the highest elevations: 8000′-9000’+. There’s not a ton of real estate in Tahoe at those elevations, so for most zones, this won’t be beneficial for the snowpack.

Models are in fair agreement on the positioning of precip. through Sunday evening (12/21). Here’s the Euro ensemble of total precip through Sunday at 1600 PST.

In addition to the agreement on precip., guidance continues to favor well-above average temperatures through the weekend.

Why so much warmth? Much of it can be attributed back to the stubborn ridge of high pressure from the recent pattern and its affect on the jet stream. Looking at the Euro forecast of the 500mb height anomalies, the ridge doesn’t depart completely. Rather, it flattens and sags south as the trough of low pressure to the north slowly nudges its way southward.

The the white area between the blue and red creates a direct alley to the SW, and that’s where the moisture feed for the storm parade originates for the coming week. Here’s a look at the precipitable water and low level (850mb) winds across the Pacific, showing the moisture fetch with a clear AR signature over the weekend.

Even though the ridge flattens and begins making way for the trough and its associated cold air, Tahoe remains on the northern periphery where the jet is able to funnel copious amounts of warm moisture from the subtropics.

What’s more, sea surface temperatures (SSTs) in the eastern Pacific continue to be well above average. These anomalies also align with the fetch of moisture for the coming week, imparting additional warmth for the systems.

Unfortunately, warmer than average SSTs will likely act as a background warming influence for storms throughout the season.

Looking ahead into Christmas week, most models suggest that the trough progresses further south into CA, bringing colder temperatures, lower snow levels, and additional storminess. However, this is delayed from what models suggested a few days ago, so the arrival of cooler air might take some time.

So as an old fly fishing friend used to say to me as I grumbled through warm storms, “it’s good for the fish.” The mostly-rain event over the coming week will entertain the fish with higher flows, but continue to frustrate any skiers hoping for a snowpack before Christmas.

Backcountry obs:

The unrelenting ridge of high pressure responsible for weeks of warm, dry weather in the mountains and cool, clammy conditions in the Tahoe Basin has taken a heavy toll on the snowpack. Snow has melted back to dirt across the area except on the highest, most sheltered N and E facing zones above 9000′. Non-snow sports have been the preferred source of outdoor fun recently.

A morning run yesterday (12/13) along the Incline Village skyline revealed only scattered patches of snow on southerly aspects and steeply inverted temperature gradients. At 5:30am it was 31°F at lake level under dense fog and 44°F at the 7600′ TH beneath Rifle Peak!

Fortunately, a pattern change is in store over the next week that will kick out the inversions and usher in more unsettled weather and the chance of higher mountain snows towards week’s end. The peak of this early season low tide is in sight.

Weather and forecast thoughts:

The coming week (12/15-12/19) will likely start out warm and dry through most of Tuesday (12/16) before rain filters into the region Tues PM through Weds, breaking Thurs, then returning Fri through the upcoming weekend. Temps in the mountains above 7000′ will start out warm with highs in the 40s early in the week, before cooling off into the 30s towards week’s end as cooler air slowly filters in from the north. Despite the new rounds of precip., models are in good agreement that high snow levels through the work week won’t provide much opportunity for the snowpack to rebound, except in zones above 8000′-9000′.

Looking into next weekend and Christmas week, models do suggest a trough developing off the CA coast which would bring more storminess, but with colder temps and lower snow levels, potentially setting up the backcountry for the season. Just like in the late fall, it’s a good idea to take note as to which areas have snow and which are snow free to help understand potential instabilities once a new snowpack finally arrives.

Here are some visuals depicting the changes afoot this week and into Christmas week:

While the potential return of snow is still more than a week out, these are the most encouraging signs of winter’s arrival seen all season.