Forum Index > Trail Talk > Watch avalanche hazard above 5000' and perhaps especially east of the Cascade Crest
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gb
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PostFri May 08, 2020 7:31 pm 
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There has been recent accumulation of snow above about that elevation. Further, in the Teanaway, the snowpack is in no way spring consolidated. A deep fall of new snow about early April is weak but for a surface crust. It would appear this layer was faceted and as such will rapidly weaken and allow percolation of meltwater in the warm weather. I might expect the possibility of 1-2' wet slabs as a distinct possibility when warm.
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Jeff
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PostSat May 09, 2020 5:23 pm 
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I just got back from the Teanaway (May 9th). The snowpack from 5000 to 6700 was definitely consolidated as one would expect for spring. No signs of facets of new snow. Saw a single point release and a single failed cornice that didn't trigger anything. Slushy but stable. I skied all aspects except for North.
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gb
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PostSat May 09, 2020 8:27 pm 
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Well, you are wrong on that. I was there the day before. All you had to do was boot a few feet and you could see the faceted grains. You can tell them because they are large, dry, and low density - fewer bonds than you would see with either MF or rounded grains. I broke through several times. If the crust held up it was because it still froze Thursday night and east winds, which were significant in the telemetry at both Crystal and Mission, were evaporative - kept the snow surface cooler.

The skiing even Thursday with an 8500' freezing level was mediocre - the "corn" was saturated at the surface except in a few places and acted like a suction cup. In other places there was sticky new snow of from 1/2 to 6" depending on aspect. But on Thursday a cold night meant the crust was uniformly supportive on skis.

Tonight with a 12,000' freezing level and clouds it won't freeze.

This should be the spring avalanche cycle this year. That will also be true above 5500 to 6000' near and west of the crest because it has just not been this warm this year and there have been recent snows.

A good simple way of judging if a snowpack is spring consolidated is to see if somewhat shaded rock faces still hold much snow. When you see that they don't then the snowpack will have undergone significant consolidation. Compare Hawkins and Three Brothers as an example.
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forest gnome
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PostSat May 09, 2020 9:47 pm 
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Mmmm obviously the avie cycle is going to be serious this year..did anybody dig a simple pit?
Sounds serious with the 2 spring storms we've had new snow on top of hoar or other crystals..1 to 2 ft. Slabs sounds right.

Sounds like clear evidense of some bad snow by just kicking the snow..if u know what to actuelly look for...not just some random signs of stability.

I was rather suprised looking at a recent trip report & the slopes involved..though it can vary from area to area we have had several clear days followed by feet of new snow...that alone tells me nothing is stable right now even taking into accountil the melt freeze...

Have to actually look below the surface...
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MangyMarmot
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PostTue May 12, 2020 8:50 am 
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Got back from a few days in the Methow. Saw no recent slide activity. Did see cornice failures. Things are melting out fast.
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PostTue May 12, 2020 9:53 am 
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MangyMarmot wrote:
Got back from a few days in the Methow. Saw no recent slide activity. Did see cornice failures. Things are melting out fast.

The Methow was somewhat different in that the big dump was in the Middle to South Cascades, so more consolidation of the new snow occurred on the east side to the north. The freezing level was also lower and was supposed to have cooled more overnight I think it was Friday night (UW MM5) in the north: 8000-8500' vs 11,500 to 12,000'.

The other thing that happened that was not predicted in weather models were strong east winds beginning Friday. They were forecast at about 10-12 mph and ended up being 20-25 mph (Mission Ridge telemetry being the best proxy for the Teanaway). What that did was cool the snow surface and evaporate surface moisture. That was not enough apparently by Saturday afternoon and Sunday, when my friends reported that it had turned to mush even in the east side Teanaway. Having skied Thursday, it may have actually have wetted more Thursday than Friday because Thursday was very windless. It did not surprise me that the skiing was still good Friday - I just didn't ski a second day because I was not that motivated after mediocre skiing Thursday.

Most likely the softest snow was at higher elevations just west of the crest with the high freezing levels around 12,000' and the descending warm air from east winds. It would be interesting to see a trip report from Shuksan, Baker, Eldorado, or Sloan. The faceted layer I saw in the Teanaway, however, would not have been found likely west of the crest (lot's of clouds and some precipitation in the preceding period, typical of the west side).

I did avalanche courses for fifteen years or so in the Blewett area and the response to radiational cooling and subsequent faceting in a snowpack of around 40" was fascinating. I learned that from radiational cooling (clear skies) that the snow surface temperature was typically 7C cooler than the air temperature (absent direct sun). Since the average snow depth was about 100cm, and the average winter temperature is likely around - 4 C or so at 4000-5000'. The temperature gradient was not 4 C/M but rather around 11/C meter. Hence, the threshold for creating faceted grains was on average met for a medium density snowpack and clearly exceeded in colder periods. The snowpack could easily lose 1/2 it's strength (approximated in shoveling) in one week. This is the origin of faceting on the east slopes except high elevations, where it is colder.

An interesting aside is that in 1980-81 I spent the winter in Sun Valley and several times dug snowpits in three distinctly different locations with average snowpacks of 4', 5', and 6-1/2-7' near Galena summit, maybe 8500'. The 4' snowpack was nothing but large grained depth hoar to 7mm; the 5' snowpack was very dangerous with a an overlying slab over the top of heavily faceted/depth hoar-treacherous and scary; the 7' snowpack was actually quite strong.....
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Forum Index > Trail Talk > Watch avalanche hazard above 5000' and perhaps especially east of the Cascade Crest
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