THIS SNOWPACK SUMMARY EXPIRED ON March 19, 2018 @ 8:25 am
Snowpack Summary published on March 17, 2018 @ 8:25 am
Issued by Ryan Lewthwaite -

bottom line:

The two storms from this week have accumulated around 87cm (34") of low density new snow. Yesterdays observations saw moderate winds & blowing snow with 3" falling per hour. There will be much avalanche activity seen today as we get a glimpse into the alpine. Play it conservative. Slopes are loaded with wind & storm slabs ripe for release, dont be the straw!

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 winds & blowing snow have created very large, elongated wind slabs. Predominately winds were out of the Southwest & have loaded aspects from the NW-NE-S, although swirling winds were observed. Going off piste today will require you to investigate the new snow for instabilities. Look for: mid-storm & recent avalanches, dense snow sitting atop loose powder, snow pillows & unique texture of the surface snow. Expect drifted areas to hold much more snow than fallen accumulations, increasing the destructive potential of an avalanche. 

Avalanche Character 2: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

Up to 34" of low density new snow will be on the mountains. This new load rests on a melt-freeze crust which could act as a smooth bed surface for avalanches. Transport of this snow is actively occuring with terrain traps & features potentially holding pockets of very deep, unstable snow. Time is needed for this avalanche problem to decrease.

Avalanche Character 3: Cornice
Cornice Fall avalanches are caused by a release of overhanging, wind drifted snow. Cornices form on lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth from wind drifting, rapid warming, or during rain-on-snow events. Cornices may break farther back onto flatter areas than expected.

The build-up of large cornices is eminent. These unsupported collections of wind driven snow are typically a problem for us in the BWRA. The steep terrain & exposed ridgelines form very dramatic cornices that break & initiate large avalanches, often propagating slabs. Always look for these signs & give cornices a wide birth, they can release farther back on a ridge than expected.

Snowpack Discussion

The new snow will be unstable & highly likely to avalanche off steep slopes for the next couple days. Our avalanche hazard encompasses problems such as: Wind slab, Storm slab, Cornice, Loose dry, & the lingering Deep slab cannot be ruled out. Do not gamble with the unknowns, make safe decisions. If we see clear skies & warm temps tomorrow look for Loose wet avalanche activity.

recent observations

Since Wednesday the BWRA has received around 87cm (34") of low density snow. The snow-water-equivalent is averaging 3.5- 4". Yesterday proved to be an adventure with almost 3" per hour & blowing snow, visibility was very poor. Avalanches were not observed due to visual restrictions, although they are definately occuring on all aspects & elevation bands.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 14 deg. F.
Max. temperature in the last 24 hours: 24 deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours: mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: 16 inches
Total snow depth: 74 inches
weather

The main storm system has moved through our region leaving behind an unsettled air mass & convection driven snow for today. We could see up to an additional 3" of accumulation throughout today with clearing skies tomorrow. Winds will be moderate out of the Southwest, with strong gusts in the alpine this morning. It will be mostly sunny for the start of the week with an Atmospheric River moving in by Tuesday with rain & snow showers.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Mostly cloudy with scattered snow showers. Cloudy with scattered snow showers late. Partly cloudy.
Temperatures: 22 to 28 deg. F. 3 to 8 deg. F. 29 to 35 deg. F.
Wind direction: Southwest Light winds Light winds
Wind speed: 10 to 15 mph; gusts to 40 mph decreasing to 25 mph later Light winds Light winds
Expected snowfall: 3 in. 2 in. 0 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Mostly cloudy with scattered snow showers. Cloudy with scattered snow showers late. Partly cloudy.
Temperatures: 15 to 20 deg. F. 0 to 5 deg. F. 22 to 27 deg. F.
Wind direction: Southwest West Northwest
Wind speed: 20 to 30 mph; gusts to 50 mph decreasing to 10 to 15 mph; gusts to 30 mph later 10 to 15 mph becoming light 10 to 15 mph; gusts to 25 mph becoming light
Expected snowfall: 3 in. 2 in. 0 in.
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.