Tahoe Backcountry Snow

0430 temp. at 6350′ in Carnelian Bay: 29.5 deg. w/ moderate snow

24 hr. new snow: 10″ from 0800 2/29 – 0800 3/1

Backcountry obs.:

The storm wasn’t coming in terribly hard this morning, so I decided to head out to Incline Peak to have a look-see. At about 7000′, conditions on Mt. Rose Highway deteriorated quickly with heavy snowfall and whiteout conditions. It was 23 deg. at the turnout and had not yet been plowed. Drifts were building in the roadway, so I opted to turn around and tour from home.

First tour of the season from the house! A fairly dense and right side up 10-12″ of new snow had fallen in the backcountry above Carnelian this morning. Coverage in this area pre storm was a mixed bag of bare ground and lumpy, crusty snowpack 1-3′ deep. Because the area is generally a S aspect, open windward zones were bare ground until this morning. Needless to say, coverage is improving and the area provided some mellow powder turns.

Weather and forecast thoughts:

Up to this morning, snowfall totals so far were on the lower end of the forecast amounts. Snow came in consistently yesterday, but as graupel and small, icy flakes. Temps. flirted with freezing in the late afternoon, but rose again to 32.4 deg. through the evening as bands of snow raked the area.

Starting at dawn, snowfall character has changed from dense, graupely snow, to a flakier, fluffy heavy snowfall, and accumulations will likely reflect the change.

Today expect snow to pick up in intensity as the heart of the multi-day storm arrives this afternoon through Sat. AM. Temps. today may nudge freezing at the lake in the early-mid afternoon, but will quickly crash back into the 20’s this evening with the arrival of the cold front. Heavy snowfall will become more consistent and reach rates of 3″ per hour, possibly up to 5″ per hour during the evening and overnight hours. These rates will be sustained as the cold front and unstable cold core of the storm behind the front arrive into Tahoe.

The airmass behind the cold front traces its origin to the Bering Sea and has traveled SE across the Gulf of Alaska over the past week. This trajectory makes the air hitting the Sierra cold, unstable, and incredibly moisture rich. Add the extra orographic lift that the range provides and boom: feet and feet of snow for Tahoe. Praise!

Winds will also pick up again this afternoon, creating the much-advertised blizzard conditions. It’ll be a great Fri. night to sit back with a whiskey, beer (or both) in front of a cozy fire.

Tomorrow morning will start out with snow dumping (3-5″ per hour) that may ease just a bit for the afternoon. This is relative, however, as rates of 1-3″ per hour do still qualify as respectable to ‘dumping’. Temps will not get out of the 20’s around lake level and gusty winds will continue. Snow quality will improve on this end of the storm as snow/water ratios rise into the 15/1 to 18/1 neighborhood.

The storm continue Sat. PM and Sun. Snowfall will turn more showery on Sun. and Sun. night with cold temps. prevailing. More snow is possible later next week.

For now, it’s time to sit back and enjoy the storm we’ve been waiting for all season.

0430 temp. at 6350′ in Carnelian Bay: 37.3 deg. & 80% RH

0515 temp. at 8650′ Tamarack TH: 27 deg. w/ graupel and mixed precip.

Backcountry obs.:

The much-advertised storm had just started to arrive this morning in the Mt. Rose backcountry with strong SW winds, dense fog, and waves of mixed precip. (graupel, icy snow, riming mist and freezing rain). Despite temps. being well below freezing, frozen droplets accumulated on my skis while skinning up in the parking lot and added a light sheen to snow surfaces. My car was covered in a textured glaze of graupel and freezing rain when I returned around 0700.

Much like Mon. 2/26, crusts reigned on all aspects of the zone with only a few isolated stashes of cold powder in true north facing trees. Accumulating graupel and whatever else remained available for wind transport whipped through the forest and along ridge lines with each blasting gust. Wind gusts on adjacent Slide Mtn. not surprisingly flirted with hurricane force (75 mph) throughout the early morning. The jet like roar of winds raking Galena Peak accompanied my entire tour.

Any new snow today is falling mainly on crusty surfaces or old, cold powder in north facing chutes and heavily sheltered, forested areas. The mixed bag coming out of the sky early in the storm may help bond new snow to the old surfaces, but regardless, the amount of anticipated new snow will create avalanche cycles throughout the event.

Weather and forecast thoughts:

It’s pretty remarkable how little has changed in the forecast for the storm over the past few days, especially in the last 24 hours. Take a look at yesterday’s post for the play by play breakdown.

In short, from now until Sun. AM, expect between 3-5′ in Tahoe communities around lake level. 5-10′ can be expected above 7000′ with greatest amounts along the crest and NW of the lake. (It will be very interesting to see what the Central Sierra Snow Lab reports on top of Donner by Sun AM.)

Whatever mixed precip. may be falling currently below 6500′ will transition to all snow and intensify throughout the day and into tonight. Snowfall rates may peak at 5″ per hour Fri.-Sat AM, before dropping back to more civilized 1-3″ per hour rates through Sun/Mon.

A break looks likely for the beginning of the week until another system moves in from the NW around midweek bringing renewed chances for more snowfall. Signals for the midweek storm are not nearly as strong as the current system, but do bear watching.

For now, it’s time to watch the snow fall.

0600 temp. at 6350′ in Carnelian Bay: 27.0 deg. & 80% RH

No backcountry obs. today

Weather and forecast thoughts:

Today is the last calm day before the big storm comes in tomorrow. Expect sunny skies with highs in the 30’s and 40’s from the lake to the backcountry. Winds and clouds may be on the increase this afternoon and into tonight as the most significant storm of the season approaches.

It’s been a tough year to get excited about incoming storms. That said, it’s time to get excited. Models are in remarkable agreement that the largest and most impactful storm of the season will hit the Sierra starting Thurs. and continuing through the weekend, maybe beyond. The most intense period of heavy snowfall will be Fri night into Sat morning with snowfall rates of 3-5″ per hour along with strong winds that will create blizzard conditions. Expect snow totals of 2-4′ at lake level with 4-8′ above 7000′, especially along the crest.

Whereas model agreement throughout the season has been so rare, forecast models for this storm sequence are in great agreement across the various suites and from run to run. It’s this consistency that gives some pretty solid forecaster confidence in the fact that we’re going to get hammered.

For example, the Euro ensemble for total accumulated precip. from Thur.-Tues. at midnight shows 6-7″ of liquid precip. for the NW side of the Tahoe Basin. The GEFS (American model) ensemble shows 5.5-6.5″ of total accumulated precip. for the same area. I haven’t seen that sort of agreement, not to mention amounts that high, all season. To convert that amount into snowfall, use a 12:1 ratio just to be safe. That comes out to 6-7′ by storm’s end, and that’s with a conservative snow/water ratio.

In addition to the heavy snows, the storm will have sustained high winds throughout the event, bringing blizzard conditions across the range. Traveling during the storm is being discouraged by authorities and the wind/snow combo will almost certainly close passes and bring down trees and limbs, affecting utility infrastructure. With that in mind, today will be a good day to stock up on firewood, whiskey, gas and food (in that order).

So how’s it going to go? Increasing winds this afternoon and tonight with presage the arrival of the storm and increase into Thurs. Snow will move into Tahoe on Thurs. late morning from the NW with snow levels around 6000′. I wouldn’t be surprised if a few rain drops mixed in at the onset, but will quickly transition over to snow. Temps will likely begin falling throughout the afternoon as snow rates pick up into the 1-3″ per hour range. Snowfall will intensify Thurs. night into Fri., then peak Fri. night into Sat. at rates between 3-5″ per hour. Colder air will filter into the system Fri., boosting snow/water ratios through the end of the storm. Snowfall will become more showery in nature into Sun. and Mon., before picking up yet again with another system or two for the middle of the week.

Needless to say, this storm will create a large avalanche cycle with many zones sliding repeatedly with such intense snow loading. The storm appears to come in rightside up with denser snow at the onset, becoming colder, lighter and drier as the event wears on. Despite this, storm slabs and wind slabs will likely initiate unstable backcountry conditions in any areas steep enough for fun skiing.

For now, it’s time to enjoy one last day of glorious Sierra sunshine and pre-storm anticipation. A big one’s en route that might just set this season straight and put us in great position for spring.