THIS SNOWPACK SUMMARY EXPIRED ON April 10, 2019 @ 7:42 am
Snowpack Summary published on April 8, 2019 @ 7:42 am
Issued by Ryan Lewthwaite -

bottom line:

We have seen an abundance of avalanche activity, in a variety of forms over the past week in the BWRA. Warming temperatures, sun, strong winds, & modest precipitation has allowed both natural & human triggered avalanches to occur on terrain steeper than 30 degrees. Use wise terrain selection & timing to avoid the avalanche issues at hand. One-half mile of plowing has been done from the trailhead up Hwy 108 West.

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.

Overnight temperatures staying above freezing has the snowpack in constant melt-out. On all aspects & elevations expect to encounter Loose Wet snow grains that can allow your track or skis to penetrate deep. On steeper slopes this penetration can cause Loose Wet point release avalanches. If enough cohesion exists amongst the Wind Slab deposits a fracture could propagate causing Wet Slab avalanches. 

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.

Very large & growing Cornices are easily seen on ridgelines all over the BWRA's alpine zone. With additional loading & rapid warmth these massive collections of snow have been collapsing onto an already unstable pack with the potential to step-down into older layers.

Avalanche Character 3: 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.

Visibly the snow has been blown around to deposits on N-E aspects having been scoured by strong & moderate winds. These Wind Slabs have been releasing naturally & by human influence on above treeline N-E aspects at a common depth of around 15cm. If enough rapid warming is introduced these dry slabs can become lubricated to the point of failure, avalanching as Wet Slabs, as seen with the Fishes Tooth Bowl avalanche.

Snowpack Discussion

Heat, Wind, Sun, & Precipitation are all collectively working to provide us with new avalanches daily. On all aspects & elevations rapid warming from sun & air temperature has the snowpack in constant motion with no refreeze in two nights. The warmth & sun have caused numerous Loose Wet avalanches & is degrading snow bridges. Strong ridgetop winds have cast loose dry snow into Wind Slab deposits above treeline on aspects N-E. Within the recent snowfall a density change, 15cm deep, has been observed as the sliding surface for Wind Slab & Wet Slab avalanche activity. Growing larger each day are the Cornices at ridgeline, some falling & entraining snow for a descent of up to 1000' in the Leavitt Cirque. Expect new snow & rain to effect the snowpack, making it even more reactive to natural & human triggered avalanches. 

recent observations

~4/6 Avalanche activity continues with several new releases observed. Issues at hand are: rapid warming causing Loose Wet, Wind Slabs on N-E aspects, & large Cornices falling.

~4/3 Wet Slab avalanche above the moto-PCT crossing in Fishes Tooth Bowl. Shallow in depth (15cm) but propagated wide across the bowl 2000'.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 42 deg. F.
Max. temperature in the last 24 hours: 49 deg. F.
Average wind direction during the last 24 hours: West
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: 0 inches
Total snow depth: 94 inches
weather

Sunshine & above freezing temperatures for a few days. Overnight temperatures have not been below freezing for two nights in a row, leaving the snow in continuous melt-out. Swirling winds yesterday were moderate to strong in the alpine with blowing snow. The rate of melting has roughly been 2-3" per day with Leavitt Snotel still reading 203"! A cold front pushes its way into our area today with modest precipitation & intense winds. Rain, snow & thunderstorms are all possible.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Monday Monday Night Tuesday
Weather: Mostly cloudy. Snow Level 10000' Increasing clouds with rain & snow developing late. Snow Level falling from 9500' to 8000' late Partly cloudy with diminishing snow showers & the possibility of a thunderstorm. Snow Level Below 7000'
Temperatures: 46 to 56 deg. F. 26 to 34 deg. F. 30 to 40 deg. F.
Wind direction: Southwest Southwest West
Wind speed: 15 to 25 mph; gusts to 40 mph 20 to 35 mph; gusts to 70 mph 20 to 30 mph; gusts to 55 mph
Expected snowfall: 0 in. 1 in. 2 in.
For above 10000 ft.
  Monday Monday Night Tuesday
Weather: Mostly cloudy. Snow Level 10000' Increasing clouds with rain & snow developing late. Snow Level falling from 9500' to 8000' late Partly cloudy with diminishing snow showers & the possibility of a thunderstorm. Snow Level Below 7000'
Temperatures: 36 to 46 deg. F. 22 to 28 deg. F. 24 to 32 deg. F.
Wind direction: Southwest Southwest
Wind speed: 20 to 35 mph; gusts to 55 mph 30 to 50 mph increasing to 40 to 55 mph; gusts to 80 mph! 25 to 40 mph; gusts to 60 mph
Expected snowfall: 0 in. 1 to 3 in. 2 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.