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target on sight

By ccrossen | December 21, 2012

Tahoe is about to get slammed. This is a lot of snow for a two-two and a half day storm. Forecast holding, with the only major changes being to hold the storm back a bit and to condense the timeframe. Looks like snow should start up midday today, and continue steadily, with some very heavy periods, from now until Sunday night, very early Monday morning. Looks like 2-4 feet at Lake level, 4-6+ feet up high. For anyone who has been skiing lately, you know that we have an amazing base going up high, so this will basically add to a huge amount of snow already. We really need snow at the lower elevations, and 2-4 feet will go a long way in setting us up for a great season, especially with the storms lined up after this one.

A major concern for the backcountry (and resorts as well to some extent), we have a very firm rain crust layer, with facets above and facets below. In all likelihood, we will have very dangerous avy conditions during this storm and afterward. We have some relatively shallow depth wind slabs forming on this rain crust layer. These slabs are very prone to sliding. When we see 2, 4, 6+ feet load onto these slabs or onto the rain crust layer itself, there is the very serious concern that the new snow simply won’t bond, or, the weight of the new loaded snow causes failure on the facet layer just below the rain crust. We’re going to have a very large, and unstable, perhaps even hair-trigger, snowpack. Nothing wants to bond to the rain crust layer, and depending on how cold this storm comes in and what is falling, we would expect to see a lot of natural slide activity as the snow loads up, is affected by high winds, and lets go. We are actually looking at a very scary scenario that should be given the utmost respect. Once this and next week’s storms clear out and we start exploring again, we’re going to have to spend some time figuring out where things stand. I would imagine we’ll see some very large natural slides in places where we haven’t seen them in awhile.

In case you haven’t seen it yet, check out John Branch’s article/multi-media presentation on last season’s Tunnel Creek avalanche in the New York Times.

NWS forecast for 7,000′ on the Crest:

Topics: Tahoe Snow Report |