THIS SNOWPACK SUMMARY EXPIRED ON March 9, 2019 @ 7:23 am
Snowpack Summary published on March 7, 2019 @ 7:23 am
Issued by Ryan Lewthwaite -

bottom line:

Southwest winds & new snow are the continued forecast through the week & into the weekend. This duo will keep the avalanche hazard focused on developing Storm & Wind Slabs on all aspects & elevations. Use periods of visibility to assess where you will travel to avoid the lingering Slabs. During storms take advantage of the many low consequence meadows that are scattered around the BWRA.

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.

Swirling winds, mostly from the South-Southwest, will continue to strip the above treeline zone & deposit snow to near & below treeline. Some Wind Slab deposits are growing very large & ominous with sharp edges & Cornices. It is very likely that if you ride upon a Wind Slab connected to a steep slope that you could trigger an avalanche up to a size D3. 

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.

Continued snowfall will exacerbate the Storm Slab problem, adding another 10" to the pack throughout today. Density changes within the uppermost snowpack will be the most reactive to avalanches. Use an inclinometer to accurately measure the slope angle to keep yourself well away from areas above 35 degrees.

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.

An amazing display of tender Cornices are available for natural or human triggering all across the BWRA. Do not approach these wind deposits as they can break above you, giving you no chance for escape. If a Cornice falls, it will likely entrain more snow upon the slope creating a very large avalanche scenario.

Snowpack Discussion

A series of well proportioned & windy storms has been constant for our region. Wind Slabs are growing ever larger & more suspect to natural avalanches large in size. Wind created features, such as Cornices, are unsupported & easily triggered by human influence. The snowpack depth ranges from 145cm to over 350cm across the mountains. Within the uppermost layers of the snowpack exist several density changes & melt-freeze crusts. Bonding in our test location seemed good enough to not initiate or propagate fractures within the top 50cms. Although perpetual snowfall & gusty winds will keep the Wind Slab problem at the top of the hazard list for all aspects & elevations.

recent observations

~Yesterdays observation found a wind effected surface snow layer that did not react to our specific snow tests. Several density changes & crusts were found in the upper 50cm of snow. Supportable snow was found near the melt-freeze crust making for good riding conditions.

~Previous observations saw evidence of rain below 8500' creating small Loose Wet avalanches. Areas of moist snow over dry snow had a potential for Wet Slabs but none were seen due to poor visability.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 23 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: South
Average wind speed during the last 24 hours: Light mph
Maximum wind gust in the last 24 hours: Strong mph
New snowfall in the last 24 hours: 9 inches
Total snow depth: 112 inches
weather

Snow will continue today throughout tomorrow with an additional 10 inches likely in higher elevations. Southwest winds will be constant & stripping the alpine of any loose snow grains & redistributing them to near & below treeline Slabs. A cold front today will keep air temperatures below normal & continued snow for the Sierra Crest through Saturday. Periods of warmth & rain can be felt in the snowpack as density changes or melt-freeze crusts.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Thursday Thursday Night Friday
Weather: Increasing clouds with a chance for snow showers throughout the day. Snow Level Below 7000' Cloudy with a chance for snow showers. Snow Level Below 7000' Mostly cloudy with a chance for snow showers. Snow Level Below 7000'
Temperatures: 29 to 37 deg. F. 14 to 20 deg. F. 20 to 30 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 25 mph; gusts to 45 mph 15 to 25 mph; gusts to 40 mph 15 to 25 mph; gusts to 35 mph
Expected snowfall: 3 in. 1 to 4 in. 1 in.
For above 10000 ft.
  Thursday Thursday Night Friday
Weather: Increasing clouds with a chance for snow showers throughout the day. Snow Level Below 7000' Cloudy with snow showers. Snow Level Below 7000' Mostly cloudy with a chance for snow showers. Snow Level Below 7000'
Temperatures: 21 to 27 deg. F. 7 to 12 deg. F. 12 to 18 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 25 to 40 mph; gusts to 60 mph decreasing to 20 to 30 mph; gusts to 45 mph later 20 to 35 mph; gusts to 45 mph 15 to 30 mph; gusts to 40 mph
Expected snowfall: 3 in. 3 to 6 in. 1 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.