Snowpack Summary published on March 18, 2017 @ 8:28 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

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On Saturday, continued warm temperatures and periods of sun will lead to possible human triggered loose wet avalanches, especially on steep southerly slopes in the afternoon.  Colder temperatures, increased cloud cover, and stronger winds will inhibit loose wet activity on Sunday and Monday and avalanche danger will be minimal on those days.  Cornice collapses will also be possible as warm temperatures weaken large overhanging cornices in the BWRA.  Other hazards to be aware of are slide-for-life conditions where surface crusts have formed overnight and have not melted out during the day.

Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Another day of above freezing temperatures and periods of strong late March sunshine will lead to the possibility of loose wet avalanches on Saturday.  These will be possible on all slopes due to warm temperatures but most likely on steep southerly facing slopes, especically in the afternoon.  Signs to look for include rollerballs, pinwheels, and sinking up past your boots in wet unconsolidated snow.  Avoid slopes where these clues exist.  Loose wet avalanches will be much less likely on Sunday and Monday as increased cloud cover, cooler temperatures, and strong winds will inhibit melting of the snow surface

Avalanche Character 2: 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.

With our long strectch of warm and sunny weather, cornices in the BWRA have been melting and losing strength day by day, trending ever closer towards collapse.  A few smaller cornice collapses have been noted around the BWRA but the big ones, especially those looming above Leavitt Bowl, have yet to collapse.  Avoidance is the best strategy in staying safe as cornice failures are notoriously unpredictable.  Look for water dripping from the bottom of cornices or icicles hanging off in the morning as this indicates that cornices are melting and losing strength.

Snowpack Discussion

Warm weather has been persistent in the BWRA for the past 10 days.  In fact, the air temperature has been above freezing since March 8th/13th at the Leavitt Lake and Sonora Pass SNOTEL stations, respectively.  Even with this consecutive stretch of warm weather, there have been no dramatic decreases in snow depth and no decrease in SWE at either station.  This shows the snowpack is still holding up quite well even with the long stretch of spring like weather.  The snow surface has been refreezing each night in most spots and sun crusts have been forming in many spots as well.  Increased winds and cloud cover have also delayed or prevented the melting of these surface crusts leading to somehwhat dangerous slide-for-life conditions on some steep slopes.  With the exception of the most exposed southerly slopes, the snowpack is still dry throughout besides surface melting, meaning the snowpack in most places is still considered a wintertime snowpack.

recent observations

Observations from around the BWRA this week revealed a relatively strong snowpack with minimal avalanche activity and few signs of instability.  Typical roller balls and pinwheels were observed on solar slopes but no large loose wet avalanche activity was seen.  The Marines have been conducting explosives testing on steep slopes above Leavitt Lake with no results. 


This morning (Saturday), temperatures in the BWRA are in the upper 30's and low 40's and stayed well above freezing overnight.  Temperatures are expected to warm into the mid to upper 40s today.  A weak system approaches our area today bringing increased cloud cover and gale force winds up high, though no precipitation is expected.  This system will usher in some colder air from the north and temperatures are expcted to be near the freezing mark in the BWRA Sunday and Monday.  A stronger storm approaches our area Tuesday through Wednesday, bringing increased chances of heavy snow.  Storm totals are expected to be around 12-18" through Wednesday.  Another storm will impact our area by next weekend bringing more snow and colder temperatures.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming mostly cloudy Mostly cloudy Mostly cloudy. Slight chance of showers in the afternoon
Temperatures: 48 to 56 deg. F. 28 to 34 deg. F. 46 to 54 deg. F.
Wind direction: SW SW S
Wind speed: 15 to 25 mph. Gusts up to 45 mph 5 to 25 mph with gusts to 45 mph 15 to 20 mph. Gusts up to 45 mph
Expected snowfall: 0 in. 0 in. 0 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming mostly cloudy Mostly cloudy Mostly cloudy. Slight chance of showers in the afternoon
Temperatures: 41 to 49 deg. F. 22 to 28 deg. F. 40 to 48 deg. F.
Wind direction: SW SW S
Wind speed: 35 to 55 mph decreasing to 30 to 45 mph in the afternoon. Gusts up to 80 mph 30 to 50 mph with gusts to 75 mph 30 to 50 mph with gusts to 90 mph
Expected snowfall: 0 in. 0 in. 0 in.

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.