THIS SNOWPACK SUMMARY EXPIRED ON December 24, 2018 @ 7:53 am
Snowpack Summary published on December 22, 2018 @ 7:53 am
Issued by Ryan Lewthwaite -

bottom line:

We won't be shut down! Snowmobiling & avalanche forecasting will still remain during the governments closure, we are here for your safety. Winds are the primary focus for causing avalanches, whether it be wind slab or cornice formation. Strong & moderate winds from the S-SW have redeposited snows to lee aspects facing NW-N-E-SE. Take your time in evaluating your chosen riding terrain, the clues are buried & somewhat difficult to discern. Dig often & in multiple locations for evidence of stability, do not guess or blindly trust old tracks. Launching sleds from the trailhead at People's Gate is still the best location, driving beyond this gate could get you stuck or on frozen slush. Carbide hill is quite bare but beyond the switchback leaves you with nowhere to go or turn around with trucks & trailers.

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.

Wind slabs of varying thickness are scattered across the BWRA on slopes facing NW-N-E-SE. The wind slabs that have released have been difficult to find & somewhat stubborn to react to tests & travel. Although seeing shooting cracks from your skis is an indicator that avalanches could occur & relocation or evaluation is your next step.

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.

Look above you! Cornices have been elongating themselves in dramatic fashion, some can be up to 30' from the edge of a ridge or terrain feature. The hollowness of these unsupported masses makes them fragile & unpredictable. There is an overwhelming possibility that if you are hit by one of these falling chucks it could cause traumatic injury or death.

Snowpack Discussion

The snowpack is an interesting mix of windpack, sun crust, & elongated well developed cornices. Any new snow sits on a variable surface layer which consists of wind-loaded snow & areas of near surface facetting. Winds from the S-SW have stripped these aspects & deposited broken snow particles & created large cornices on opposing aspects from NW-N-E-SE. Any Southern aspects that haven't been ravaged by wind have been melted by sun & refrozen as ice, which is a good bed-surface for avalanches to occur on. We have ~70cm (27") of snow depth at our Leavitt junction measuring station.

recent observations

This week we've been seeing cornice fall & wind slabs avalanche remnants on lee aspects facing NW-N-E-SE. Moderate to strong winds from the S-SW have been loading features with cornices & wind slabs that both avalanche naturally & some that are stubborn to react with snowmobile travel. Areas where facets reside below thin or reactive wind slabs could step into old snow layers and accumulate into D2 avalanches, slides that could bury a human. 

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 22 deg. F.
Max. temperature in the last 24 hours: 37 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 50 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 27 inches
weather

New snow fell in the amount of 3-4" on Monday morning & Thursday night, but the evidence has been blown around by strong to moderate winds from the S-SW. Sun has encrusted Southern aspects & sublimated blowing snow. It seems that rain has accompanied Thursdays storm up to 8500' in elevation, leaving behind a panko breading theme to surface snow.  We are anticipating snow accumulations over 6" for Monday & a white Christmas.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Sunny with increasing clouds. Mostly cloudy. Partly cloudy.
Temperatures: 39 to 44 deg. F. 20 to 25 deg. F. 38 to 44 deg. F.
Wind direction: Light winds Southwest West
Wind speed: Light winds 10 to 15 mph; gusts to 35 mph 10 to 15 mph in the morning then decreasing; gusts to 30 mph
Expected snowfall: 0 in. 0 in. 0 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Partly cloudy. Mostly cloudy. Partly cloudy.
Temperatures: 34 to 39 deg. F. 16 to 21 deg. F. 32 to 37 deg. F.
Wind direction: West Southwest West
Wind speed: 10 to 15 mph; gusts to 25 mph later 15 to 25 mph; gusts to 40 mph 15 to 20 mph; gusts to 35 mph
Expected snowfall: 0 in. 0 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.