Snowpack Summary published on January 24, 2017 @ 9:42 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

bottom line:

The avalanche danger in the BWRA will decrease through the week as the snowpack strengthens and adjusts to the new load from the previous week's storms. It will still be possible for a rider to trigger a wind slab on exposed NW-N-NE-E facing slopes steeper than 35 degrees and it is advised to avoid those slopes for the next couple of days until the wind slabs have had time to strengthen and bond to the pre-existing snowpack.

Avalanche Character 1: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Strong southwesterly winds accompanied the series of storms last week and over the weekend loading NW-N-NE-E facing slopes and stripping exposed slopes with a southerly aspect. The storm came in cold this past weekend bringing low density snow allowing for easier wind transport. Wind gusts were estimated to be near hurricane force over the weekend and visible transport of huge plumes of snow were observed on Saturday extending further down slope than usual. This week, winds are expected to veer to the E/NE and could be strong at ridge top levels which will load atypical slopes including SE-S-SW facing slopes. Look for areas of blowing snow, recent cornice formation, and wind pillows to determine specific slopes where wind slabs likely exist. Avoid travel on slopes with terrain traps below such as cliffs, creek beds, and deep gullies.

Snowpack Discussion

In the snowpack on Saturday, we found instabilities in the storm snow due to mid-storm density changes. There was also a rain crust buried about 3 ft down (probably about 5 ft down now) that formed last Wednesday and showed to be fragile with the potential to propagate a fracture. I expect the past week's storm snow to gain strength rapidly as we go through the week as well as the strength of the now deeply buried rain crust. The biggest danger out there over the next couple of days will be wind slabs on exposed upper-elevation leeward slopes. It will still be possible to trigger these but become more difficult as the wind slabs gain strength over the week.

recent observations

We have not been able to make it up to the rec area recently due to poor weather and very deep and unpacked snow on Hwy 108. On Saturday, we rode up Hwy 108 to Sardine Meadows on a previously packed road that had about 18" of new snow. Past Sardine Meadows the road had not been packed down since before last Wednesday and there was about 40" of new snow which made riding past that point impossible. I was informed by a local rider today (Tuesday) who rode up to Leavitt Lake that the groomers were out in force currently grooming 108 and Leavitt Lake Road. He saw no recent signs of avalanche activity and said the conditions were absolutely incredible. Get up here this week if you can, you won't want to miss it!

weather

Since Sunday, the BWRA picked up around 20" of new snow which came in right side up.  This brings our 5-day total (since Wed 1/18) to 70" of snow/13" of SWE at the Leavitt Lake SNOTEL station and 52" of snow/8" of SWE at the Sonora Pass SNOTEL station.  We finally get an extended break this week from storms as a large area of high pressure builds into California.  We will see a pronounced inversion set up with very cold temps in the valleys (0 to -15 F) and much more milder and pleasant temps in the mountains (15-30 F) with even warmer temps (upper 30s) expected by the weekend.  A weak distrubance moves through Thursday bringing increased clouds and only a slight chance of snow.  We will see a period of strong NE-E winds Friday with gusts up to 60 mph, but will be confined to the Sierra Crest. 

Disclaimer

This snowpack summary applies only to backcountry areas in the Bridgeport Winter Recreation Area. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.