THIS SNOWPACK SUMMARY EXPIRED ON January 8, 2019 @ 7:29 am
Snowpack Summary published on January 6, 2019 @ 7:29 am
Issued by Ryan Lewthwaite -

bottom line:

An Avalanche Watch has been issued for the BWRA & Virginia Lakes for the next 48 hours. The avalanche hazard is increasing today into tonight as we gain more snow & wind from the SW. 13 to 16" has accumulated at our Snotel sights already, with strong transporting winds from the SW increasing the size of slabs & cornices. All aspects & elevations will have newly formed storm slabs sitting on variable surface snows. Another voracious winter blast is headed for us starting midday today & expected avalanche danger could be HIGH! Southwest winds will be moving snow to lee aspects with gusts potentially reaching 125mph! Succeed when choosing riding terrain selections, practice time is over...

Avalanche Character 1: 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.

The Storm Slab avalanche problem is real & unconfined. All aspects & elevations are at risk for the next +48 hours as we will see increasing snow accumulations tonight. Remember, as a slab fails it could break above you & propagate horizonally entraining much more snow & crushing forces.

Avalanche Character 2: 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 to Gale force winds have battered the mountain environment, leaving behind deep leeward deposits & thick dicey slabs. Projected winds up to 125 tonight & the addition of up to 2' of new snow tonight is a terrible combination for avalanche potential. Expect NW-N-SE aspects to be most recently loaded with wind slab deposits. Furthermore, previous N & E winds earlier in the week had marginally lined S through W facing terrain features with transported snow.

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.

The prescence of these monsters above you should be concerning. A report of a naturally falling cornice in the Leavitt Cirque area on Tuesday was somewhat alarming. This NE facing feature will have grown more cornice exponentially with recent windy accumulations. A step-down scenario only elevates this avalanche problem.

Snowpack Discussion

"An Avalanche Watch is in Effect for the next 48 hours" Heavy snow (SWE 0.7") with accumulations above 16" has fallen overnight & much more is on tap for tonight. Winds have scoured & scalloped upper layers of the snowpack near & above treeline to a firm windpack. Whilist, wind & sun protected areas have soft snow with a possible lingering surface hoar near & below treeline. Widespread areas of variable windpack have shown near surface facets below this crust that have been reactive to moderate forces in stability tests. The liklihood of large avalanches is considerable to high in the alpine with instability rising throughout today & tonight.

recent observations

The search for good snow is concluded, after over a week precipitationless. Observations from various points in the BWRA & Virginia Lakes areas show variable snow surfaces, ranging from supportable to soft. Surface crust/facet combos can make finding safe riding terrain difficult. Storm & wind slabs will be growing hazardous atop a fickle surface snowpack. Not much is happening with round grains deeper in the pack. Large & growing larger are ominous Cornices overhanging unstable storm & wind slabs.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 19 deg. F.
Max. temperature in the last 24 hours: 34 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: moderate mph
Maximum wind gust in the last 24 hours: strong mph
New snowfall in the last 24 hours: 13 inches
Total snow depth: 37 inches
weather

A strong winter storm overnight dropped 13-16" in the BWRA & Virginia Lakes areas. An avalanche watch has been put into effect for the next 48 hours as we will recieve another large helping of snow tonight. Forecasts project Gale force winds & an estimated range of 10 to 26" for the next 24 hours. Tonight Southwest to West winds at ridgeline could gust up to 125 mph! Snow Water Equivalent lastnight was around 0.75" & the two storms could total nearly 2.0" inches of liquid. Cloudy skies & temps in the 20s with a short break during the storms today, Much Wind Expected.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Sunday Sunday Night Monday
Weather: Mostly cloudy & snowing. Snow Level Below 7000" Cloudy with snow. Snow Level Below 7000" Mostly cloudy with snow showers. Snow Level Below 7000"
Temperatures: 24 to 30 deg. F. 21 to 26 deg. F. 34 to 40 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 25 mph; gusts to 40 mph increasing to 75 mph later 35 to 55 mph; gusts to 100 mph! 30 to 45 mph; gusts to 85 mph decreasing 15 to 30 mph with gusts to 60 mph later
Expected snowfall: 2 to 6 in. 10 to 18 in. 2 to 4 in.
For above 10000 ft.
  Sunday Sunday Night Monday
Weather: Mostly cloudy & snowing. Snow Level Below 7000" Cloudy with snow. Snow Level Below 7000" Mostly cloudy with snow showers. Snow Level Below 7000"
Temperatures: 17 to 22 deg. F. 15 to 20 deg. F. 26 to 31 deg. F.
Wind direction: Southwest Southwest becoming West Southwest
Wind speed: 20 to 30 mph; gusts to 50 mph increasing to 30 to 45 mph with gusts to 85 mph later 55 to 70 mph becoming West & increasing to 70 to 80 mph; gusts to 125 mph late! 45 to 65 mph; gusts to 110 mph decreasing to 30 to 45 mph with gusts to 70 mph
Expected snowfall: 2 to 6 in. 10 to 18 in. 2 to 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.