THIS SNOWPACK SUMMARY EXPIRED ON February 3, 2019 @ 8:32 am
Snowpack Summary published on February 1, 2019 @ 8:32 am
Issued by Ryan Lewthwaite -

bottom line:

For most of today conditions will be quiet with mostly cloudy skies. Later this afternoon a front enters the region with strong winds & heavy snow potential. Tomorrow we can expect elevated avalanche activity & white-out conditions for mountainous terrain. In succession, another powerful storm is out for us starting Sunday & going through Tuesday with more feet of snow forecasted. Heed the warning of large & destructive avalanches during these storm cycles!

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.

If you hear of white-out conditions expects the transport of snow from strong winds. With snowfall estimates in multiple feet forecasted, the associated winds will create dramatically larger slabs that will be prone to avalanching naturally. Winds are projected to be strong to gale & originating from the South end of the compass. This pattern will translate to slab formations loading aspects that face W-N-E.

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.

The largest snowfall estimates are around 48" or 4' for mountainous areas above 10K. Storm snow in large quantities can exhibit like qualities, sometimes as a denser slab that will act as a weak layer on top of the snowpack. Coupled with wind effect & the potential for rain, avalanche activity will become very likely as these storms persist.

Snowpack Discussion

Surface Hoar (1-2mm) has developed below treeline on shaded aspects that receive little wind. Areas where surface crusts have formed has allowed some Dry to Moist snow grains to exists under the surface. The snowpack has started to gain the qualities of spring with melt-freeze grains near the surface & lower temperature gradients.

recent observations

A routine of spring-like conditions has melted the snow creating crusts that could gain strength with plummeting temperatures. These crusts could become the new bed-surface for avalanches as we gain heavy snow tonight. Avalanche activity has been restricted to Loose Wet occurences on sun impacted slopes. 

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 35 deg. F.
Max. temperature in the last 24 hours: 40 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: Light mph
Maximum wind gust in the last 24 hours: Moderate mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 52 inches
weather

This morning will exhibit a calm before the storm which shall arrive later this evening. A moisture rich storm will bring with it strong winds & at times Heavy snow accumulations for the ridges of the Sierra Crest. White-out conditions are expected for the mountains & lower valley rain or freezing rain below 5500'. Travel will be impacted on roads & mountains travel is not recommended due to low visibility & snow slab formation. With temperatures returning to winter-like status & successive storms we could see large amounts of snow that will take time to settle upon the landscape.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Friday Friday Night Saturday
Weather: Mostly cloudy with a slight chance for snow showers. Snow Level 7000' Cloudy with snow. Snow Level Below 7000' Heavy Snow! Snow Level Below 7000'
Temperatures: 37 to 43 deg. F. 25 to 30 deg. F. 29 to 35 deg. F.
Wind direction: South South Southeast
Wind speed: 15 to 25 mph; gusts to 40 mph later 15 to 30 mph; gusts to 45 mph 15 to 25 mph; gusts to 45 mph
Expected snowfall: 0 in. 2 to 6 in. 14 to 22 in.
For above 10000 ft.
  Friday Friday Night Saturday
Weather: Mostly cloudy with a slight chance for snow showers. Snow Level 7000' Cloudy with snow. Snow Level Below 7000' Heavy Snow! Snow Level Below 7000'
Temperatures: 30 to 36 deg. F. 20 to 25 deg. F. 22 to 28 deg. F.
Wind direction: Southwest shifting to South later South South
Wind speed: 15 to 25 mph; gusts to 45 mph increasing to 25 to 35 mph; gusts to 60 mph later 30 to 50 mph; gusts to 80 mph 35 to 55 mph; gusts to 80 mph decreasing to 25 to 40 mph; gusts to 60 mph later
Expected snowfall: trace in. 3 to 7 in. 19 to 27 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.