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.