THIS SNOWPACK SUMMARY EXPIRED ON February 10, 2017 @ 10:25 am
Snowpack Summary published on February 7, 2017 @ 10:25 am
Issued by Kyle Van Peursem - Bridgeport Avalanche Center

bottom line:

A strong series of atmospheric river events will impact our area through the rest of the week bringing copious amounts of precipitation and wind, leading to very dangerous avalanche conditions in the BWRA.

Tuesday - Thursday: Heavy precipitation coupled with very high snow levels and hurricane force winds will lead to wet slab avalanches on all aspects below 9300', storm slab avalanches on all non-exposed aspects above 9300', and wind slab avalanches on exposed NW-N-NE-E-SE aspects above 9300'. During this time, natural avalanches are likely and human triggered avalanches are very likely and have the potential to be large and destructive. Remaining off and away from all avalanche terrain will be key to staying safe in the BWRA through the rest of the week.

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.

Hurricane force winds are expected in the upper elevations of the BWRA throughout the week, with the strongest period of winds being Tuesday and Tuesday night, where wind gusts at the crest could reach nearly 165 mph! This will rapidly load all leeward slopes in exposed areas, including NW-N-NE-E-SE aspects. Most wind loaded bowls and gullies will likely avalanche naturally over the next couple of days. Due to the strength of the winds, wind slabs may also be present near and below treeline in unexpected places.

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.

Above 9300', we are expecting 3-4' of new heavy snow through Friday night. Rising snow levels will produce an upside down snowpack and cause storm snow instabilities. Look out for cracking, collapsing, and whoompfing and remain off and away from all slopes steeper than 35 degrees during the week.

Avalanche Character 3: Wet Slab
Wet Slab avalanches occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoid avalanche terrain when you see pinwheels, roller balls, loose wet avalanches, or during rain-on-snow events.

Snow levels Tuesday afternoon through Thursday will rise to about 9300' in the BWRA, meaning we will see heavy rain on snow in lower elevations. We expect snow to begin transitioning over to rain late Tuesday morning with 1.5-2" of rain expected at these elevations through Thursday, with the heaviest precipitation being Tuesday and Tuesday night. This will likely lead to the potential of large wet slab avalanches on all lower elevation aspects. These avalanches are unpredictable and can run much further than expected, similar to the large wet slab avalanche that nearly buried lower Leavitt Lake Road in early January. It is best to avoid all large avalanche paths that are below 9300' and travel quickly and one at a time if you must move through these zones.

Snowpack Discussion

The snowpack will receive a massive load over the course of the week, with numerous avalanche problems present in the BWRA including wind slabs, heavy upside-down new snow, and wet slabs due to rain on snow. Luckily, due to our deep and relatively warm snowpack, buried persistent weak layers are not present in our snowpack so these instabilities will subside rather quickly once the storm tracks pushes out of our area this weekend and next week. Until then, avalanche conditions will be very dangerous in the BWRA and it is recommended to remain off and away from any avalanche terrain.

recent observations

Over the weekend, numerous natural and human triggered wind slab avalanches were observed in the BWRA, including a rider who unintentionally triggered a cornice collapse by walking too close to the edge. Yesterday, a wet slab avalanche was observed on the slope just above the People's Gate due to heavy rain on snow.

weather

Another round of strong atmospheric river events will impact our area this week. Since Sunday night, the BWRA has already received 1.5-2' of new snow. This afternoon, a strong storm system will impact out area with rain levels rising to about 9300', or half way between the Leavitt Lake Road junction and Leavitt Lake with heavy precipitation falling through early Wednesday morning. We will see a short break during the day on Wednesday with only light rain/snow showers before the next system brings another quick round of heavy precipitation Wednesday night. The final system will approach our area Thursday night bringing more precipitation but lowering snow levels.

Storm totals:
Below 9300': ~24" snow and ~2" rain (Tuesday-Friday). 5-day Storm Total (Sunday-Friday): ~45" snow / ~5" SWE (rain and snow)
Above 9300': ~45" snow (Tuesday-Friday). 5-day Storm Total (Sunday-Friday): ~70" snow / ~9" SWE (all snow)

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 above 8900', rain below Cloudy. Snow above 9100', rain below Cloudy. Snow above 9300', rain below
Temperatures: 28-38 deg. F. 25-35 deg. F. 31-41 deg. F.
Wind direction: SW SW SW
Wind speed: 30 to 50 mph. Gusts up to 120 mph decreasing to 105 mph in the afternoon 30 to 40 mph decreasing to 20 to 30 mph after midnight. Gusts up to 90 mph 15 to 25 mph. Gusts up to 55 mph increasing to 65 mph in the afternoon
Expected snowfall: 8 to 16 in. 2-8 in. 1-4 in.
For above 10000 ft.
  Tuesday Tuesday Night Wednesday
Weather: Cloudy. Snow Cloudy. Snow Mostly cloudy. Chance of snow
Temperatures: 24-31 deg. F. 22-28 deg. F. 24-32 deg. F.
Wind direction: SW WSW SW
Wind speed: 60 to 80 mph. Gusts up to 165 mph decreasing to 145 mph in the afternoon 50 to 70 mph with gusts to 130 mph becoming southwest and decreasing to 40 to 55 mph with gusts to 105 mph after midnight 30 to 50 mph. Gusts up to 90 mph increasing to 100 mph in the afternoon
Expected snowfall: 12-20 in. 6-10 in. 2-4 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.