THIS SNOWPACK SUMMARY EXPIRED ON March 24, 2017 @ 9:36 am
Snowpack Summary published on March 21, 2017 @ 9:36 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

bottom line:

The avalanche danger will rapidly increase today in the BWRA due to the combination of heavy snow and hurricane force winds.  Human triggered avalanches will be likely and natural avalanches will be possible on all slopes steeper than 35 degrees today into tomorrow morning.  The avalanche danger will subside some Wednesday through Friday morning in between storms as the snowpack begins to adjust to the new load, but human triggered wind slab avalanches will still be possible on slopes steeper than 35 degrees.

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 SW winds in excess of 80 mph will accompany periods of heavy snow Tuesday into Tuesday night and will load exposed NW-N-NE-E-SE facing slopes near and above treeline.  Triggering these wind slabs by a rider will be likely Tuesday and Wednesday and it is recommended to remain off of any wind loaded slope steeper than 35 degrees during that time.  Clues to look for include pillowy slopes just below newly formed cornices and slopes where drifting new snow is being deposited.

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.

12-18" of dense new snow is expected through Wednesday morning which will fall on a variety of suraces, including slick sun and melt-freeze crusts that formed during last week's warm weather.  Bonding will be poor between the old and new snow interface through Wednesday and it will be possible to trigger a storm slab avalanche on all sheltered slopes steeper than 35 degrees.  Look for collapsing and cracking and avoid slopes where these clues are evident.

Snowpack Discussion

The last 2 weeks of warm spring-like weather greatly impacted the snowpack in the BWRA, with lower elevations beginning to melt out, upper elevation southerly slopes becoming nearly isothermal, and upper elevation northerly slopes still holding on to dry snow throughout the snowpack.  The Leavitt Lake SNOTEL station finally reported an air temperature at the freezing mark this morning after being above freezing for 12 days.  Surprisingly, due to shading and aspect, there was little melting over these 12 days as the station reported no loss of SWE.  Further down at the Sonora Pass SNOTEL station, some melting has been occuring as the SWE decreased by about 2" last week.  Cloud cover and winds have inhibited a lot of the surface melting this past week and over the weekend leaving sun and melt-freeze crusts on a number of slopes in the BWRA. 

recent observations

Observations made on Saturday in the BWRA revealed a variety of conditions including a wet springtime snowpack on lower elevation and southerly facing slopes and a mostly dry wintertime snowpack, with the exception of a thin layer of wet snow on the surface, on slopes with more of a northerly component.  Stability tests showed some instability with very wet snow near the surface on southerly slopes but also showed no propensity for propagation.  The rest of the snowpack was strong and quite stable. 

weather

A series of storms will impact our area through early next week, with the first storm hitting our area today.  We have already picked up between 2-5" of wet heavy snow in the BWRA this morning with an additional foot expected through Wednesday morning.  Luckily snow levels will be dropping through the day today and overnight leaving us with some lighter powder on top of denser snow.  We'll see a brief break in snow Wednesday morning with snow showers developing in the afternoon bringing an additional 2-3" of light powder.  Winds will be very strong Tuesday with gusts approaching hurricane force at the ridgetops, tapering down Tuesday night into Wednesday.  Another system approaches our area during the day on Friday through Saturday morning bringing the potential of another 6-12" of snow to the BWRA.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Tuesday Tuesday Night Wednesday
Weather: Cloudy. Snow and rain in the morning. Slight chance of thunderstorms through the day. Widespread showers in the afternoon. Mostly cloudy then becoming partly cloudy. Chance of snow showers and slight chance of thunderstorms in the evening, then slight chance of snow showers after midnight. Partly cloudy then becoming mostly cloudy. Chance of snow showers in the morning, then snow showers likely and slight chance of thunderstorms in the afternoon.
Temperatures: 30 to 36 deg. F. 22 to 28 deg. F. 34 to 40 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 25 mph with gusts to 50 mph 15 to 25 mph with gusts to 50 mph 10 to 15 mph with gusts to 25 mph in the morning becoming light.
Expected snowfall: 5-10, 30% chance 10-14 in. 1-3 in. 1-2 in.
For above 10000 ft.
  Tuesday Tuesday Night Wednesday
Weather: Cloudy. Snow in the morning. Slight chance of thunderstorms through the day. Widespread snow showers in the afternoon. Mostly cloudy then becoming partly cloudy. Slight chance of thunderstorms in the evening. Slight chance of snow showers through the night. Mostly cloudy. Chance of snow showers in the morning, then snow showers likely and slight chance of thunderstorms in the afternoon.
Temperatures: 28 to 34 deg. F. 17 to 23 deg. F. 24 to 32 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 40 to 60 mph with gusts to 90 mph 40 to 60 mph. Gusts up to 100 mph decreasing to 80 mph after midnight 20 to 30 mph with gusts to 60 mph decreasing to 10 to 15 mph with gusts to 30 mph in the afternoon.
Expected snowfall: 6-12, 30% chance 12-18 in. 2-4 in. 2-3 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.