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Weather Summary

Classic springtime in the mountains. Morning Stanley obs: Intense snowfall between 0830 and 1130 brought about 15cm of new snow. A fair bit of blowing going on during this storm, but it was fairly gusty and loading was irregular.
Afternoon field obs: Short periods of S2-S5 showers during the afternoon brought an additional 3-4cm. Periods of gauzy clouds, ice crystals in the air, and variable sunshine between squalls. Winds were generally calm during the afternoon, with one notable 15-20 minute period of blowing snow. Temperatures dropped throughout the tour, it was quite cold by sunset.

Avalanche Observations

Avalanche Observation Comments:

I observed several D1 dry loose slides that had occurred in steep terrain. I heard and then watched one of these release shortly before sunset on the NE side of Thompson. I also triggered several D1 dry loose slides in terrain steeper than about 38 degrees.

Snowpack Observations

The big storm brought significant wind on Monday and Monday night, along with about 3-5cm of dense snow. It rained in town (Stanley) on Monday night, but unlike the upper elevation rain event I observed on Copper, this rain only made it up to about 6,900' or so. This early snow generally seemed to bond well with crusts on solars and I was able to easily set steepish skin tracks on slopes with crusts thanks to this. Tuesday morning's storm brought roughly 15cm of new snow to the Fishhook area of the Sawtooths, with most of this falling during the morning, and then some continued trickle during short but intense flurries in the afternoon. This post-frontal snow fell largely without wind. I did observe some large-scale drifts and dunes in upper elevation terrain above the Marshall drainage, I suspect the slabs that had formed here were very soft. I encountered one of these soft slabs in profile on a steep slope that faced SE. It produced some minor cracking but there wasn't nearly enough meat to the slab to create an avalanche problem. There was a good bit of rime on rocks and trees, including a 1+cm thick grey water-ice rime on trees in Profile. The air was clearly very wet, I'm not sure why it refused to precipitate for us during the first 3/4 of the storm... So it goes, glad it decided to snow at the end. Looking across the valley at the White Clouds, it appears like they got pretty well coated by this storm.

Avalanche Problems

I entered the field with wind slabs and dry loose on my problem list. I anticipated that slabs would be a bit touchier than a simple wind slab, thanks to weak surfaces underneath, particularly where the new snow fell on crusts and facets. However, in the absence of wind there was no slab in the new snow where I traveled and I did not encounter a wind slab problem. Dry loose problem was specific to terrain steeper than about 38 degrees. Here, triggering small sluffs was easy. These picked up speed relatively quickly, but most of the sluffing was occurring in the upper 10cm of the new snow and the "bed surfaces" of these sluffs skied quite well, even where icy crusts were present underneath.

Terrain Use

I cautiously and selectively entered avalanche terrain that had not been loaded by winds during this storm. I would not have felt comfortable entering large, consequential terrain that had been wind loaded.