THIS SNOWPACK SUMMARY EXPIRED ON April 7, 2019 @ 7:26 am
Snowpack Summary published on April 5, 2019 @ 7:26 am
Issued by Ryan Lewthwaite -

bottom line:

Wind Slabs on N-E aspects are the primary hazard. A unique set of variables allowed numerous avalanches to occur on aspects N-E, as Wind Slabs turned into Wet Slabs with rapid warming. Snow below 7500' is melting quickly with warm temperatures, rain & the plowing of Hwy 108. Parking will continue from the People's Gate Trailhead as Caltrans has only gained a short distance up the road.

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.

The Wind Slabs that formed on Tuesday became unstable by rapid warming & intense sun just following deposition. Many areas did not shed the surface Slabs & may hold the potential for human triggered avalanches, mainly on N-E aspects above treeline. Southwest winds will continue to load the Wind Slabs on N-E aspects with an additional few inches tonight. Avoid steep terrain above treeline that hadn't previously avalanched, as well as newly formed Wind Slabs.

Avalanche Character 2: 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.

At elevations below 7500' expect rain & above freezing temperatures. At the Sonora Snotel the temperature ducked just below freezing for a couple hours. This zone of rapidly melting snow could begin to show the objects that were beneath the pack all season including: rocks, logs, Orange Roadside Markers, CREEKS, & pavement.

Snowpack Discussion

Surface instabilities are the main focus for travelers in the BWRA. 23cm of new snow on Tuesday was strewn about by wind and zapped by the sun. Many new avalanches have been observed to run naturally with a couple human triggered outlyers. The timing of snow & rapid warm-up caused Wind Slabs to lose cohesion & fail as Wet Slabs. A density change within the storm snow is the interface for avalanches 15cm down, taking moderate forces to cause collapse. The slopes facing N-E are most prone to Wind Slabs & is where you can find remnants of the Wet Slab issue. Clouds will subdue the Wet Slabs near & above treeline but keep them as fickle Wind Slabs for the next few days. As we gain a couple inches of new snow on these developed Wind Slabs, expect them to become more reactive. Below 7500' the snowpack is going to get rain & will be melting quickly.

recent observations

~4/4 Numerous avalanches observed. N-E aspects found previous Wind Slabs which had rapidly warmed causing Wet Slab avalanches. Fishes tooth area had a R2.5-D2 Wet Slab. Leavitt Cirques North face had a skiier triggered Slab avalanche which took the individual for a ride.

~4/1 Loose Wet avalanches on aspects that gain intense sun.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 30 deg. F.
Max. temperature in the last 24 hours: 41 deg. F.
Average wind direction during the last 24 hours: Southwest
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: 97 inches
weather

Clouds will build today as an approaching low pressure system envelopes our region. Low elevation rain & mountain snow can be expected in meager amounts. Wind will become Moderate to Strong from the Southwest, gusting to 50 mph in the alpine. The transition zone from rain to snow will be around the 7000' mark. Snow is rapidly disintegrating below 7000' as well as plowing operations are stripping the road of snow from the trailhead, west.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Friday Friday Night Saturday
Weather: Increasing clouds with widespread snow showers in the afternoon. Snow Level Around 7000' Partly cloudy with scattered snow showers. Snow Level Below 7000' Mostly cloudy with isolated snow showers. Snow Level Around 7000'
Temperatures: 32 to 42 deg. F. 20 to 26 deg. F. 37 to 47 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 25 mph; gusts to 45 mph 15 to 25 mph; gusts to 45 mph 15 mph; gusts to 35 mph
Expected snowfall: 2 in. 1 in. trace in.
For above 10000 ft.
  Friday Friday Night Saturday
Weather: Increasing clouds with widespread snow showers in the afternoon. Snow Level Around 7000' Decreasing clouds with scattered snow showers. Snow Level Around 7000' Mostly cloudy with isolated snow showers. Snow Level Around 7000'
Temperatures: 24 to 29 deg. F. 15 to 20 deg. F. 29 to 34 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 15 to 30 mph; gusts to 50 mph 15 to 30 mph; gusts to 45 mph 15 to 30 mph; gusts to 40 mph
Expected snowfall: 2 in. 1 in. trace 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.