THIS SNOWPACK SUMMARY EXPIRED ON January 8, 2018 @ 11:18 am
Snowpack Summary published on January 6, 2018 @ 11:18 am
Issued by Ryan Lewthwaite -

bottom line:

Still CLOSED... Although the weather has begun to cooperate with snow falling currently in the BWRA, it is not enough to open. Temperatures near or above freezing & new snow in the amount of 7-9" have developed overnight. The likelihood of seeing or producing loose wet avalanches on slopes steeper that 35 degrees today is good. Winds have been broadcasting the precipitation into deposits on leeward slopes from Northwest through Southeast aspects. Previously deposited wind slabs, on the fore mentioned aspects, will likely remain our snowpack's persistent slab hazard. It is recommended to stay out of avalanche terrain & off steep slopes until you can develop a full understanding of what you are riding.

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.

A new snow accumulation of 7-9" fell overnight with warm temperatures & strong winds. Nearly 2" of water equivalent was recorded, meaning the new snow is wetter & less consolidated than what it sits on. The snowpack that exists is highly variable from one location to the next, or it may be bare. Sun will make this snow unstable on slopes steeper than 35 degrees.

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.

You can't have 50 mph winds without the formation of wind slabs. Winds from the south & west have loaded slopes in contrast from the Northwest through Southeast aspects. Cross-loading of gullies & cornice creation will be apparent out there today as wind driven snow moves around the landscape. Triggering a wind or persistent slab can be possible from much lower on the slope than you anticipate.

Avalanche Character 3: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.

The snowpack has had trouble maintaining a good routine this season. Fluctuations & above normal temps, prolonged dry periods, & high winds have created a structure that is poor & new loading could prove this. Facet/ crust combos are lingering within the spatially variable snowpack & likely will help propagate avalanches at these layers. Although not reactive everywhere, deeper pockets of instability exist, therefore avoiding avalanche terrain is a safer bet.

Snowpack Discussion

A lot is going on in a relatively small amount of snow. We are finding the base of our pack is pretty glued into place but above that is layering crusts with faceting snow grains in the mix. Tests have shown a consistent failure at 88cm (35") from the bottom up, with moderate influence. Last evening & todays new snow will be concerning as it has come in warm & wet & sits upon a poor structure.

recent observations

Wednesday night pushed out 1.5" of snow in places but winds have cast it around. Overnight new snow fell above 7500' in some amounts as deep as 9" can be found. Wet & unconsolidated avalanches can be seen on steeper slopes. Blowing snow & deposition is occurring especially above treeline.

weather

Snow has returned to the Central Sierra Mountains! Stations in the BWRA report 7-9" of new snow accumulated with temperatures near or above freezing. The moisture will continue throughout today & will be ending this evening as skies clear. Tomorrow we can see sunshine until the next band of precipitation moves in. Winds today will be strong out of the Southwest trending West with 30 to 50 mph & gusts near 80 mph! Winds shall die-off this evening & again ramp-up as the next system enters our zone. Temperatures are still unseasonably warm & rain has accompanied the snow in elevations from 8500' & below.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Mostly cloudy with snow & rain showers tapering off this afternoon Partly cloudy then clearing with a slight chance of snow late evening Sunny then increasing clouds
Temperatures: 38 - 46 deg. F. 25 - 30 deg. F. 44 - 52 deg. F.
Wind direction: Southwest West Light winds
Wind speed: 15 to 25 mph; gusts to 65 mph decreasing to 50 this afternoon 10 to 15 mph; gusts to 40 mph becoming light later Light winds; gusts to 25 in the afternoon
Expected snowfall: 2 to 5" in. 1" in. 0 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Mostly cloudy with snow tapering off Partly cloudy then clearing with a slight chance of snow Sunny then becoming partly cloudy
Temperatures: 31 - 36 deg. F. 23 - 28 deg. F. 37 - 42 deg. F.
Wind direction: Southwest West Southwest
Wind speed: 30 to 50 mph; gusts up to 80 mph! 25 to 35 mph; gusts to 55 mph. This evening 15 to 25 mph; gusts 35 mph 15 to 20 mph; gusts to 30 mph
Expected snowfall: 2 - 6" in. 1" 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.