THIS SNOWPACK SUMMARY EXPIRED ON January 12, 2018 @ 10:47 am
Snowpack Summary published on January 10, 2018 @ 10:47 am
Issued by Ryan Lewthwaite -

bottom line:

CLOSED!! The bottom line should be replaced with "Where's Snow-Line." Our expectations were dashed as we entered the BWRA on foot, the last two days. Rain has decimated the new snow & shrank the volume of existing snowpack at lower elevations. Loose wet avalanches are occurring on all aspects at & above treeline, with the rare Wet Slab showing itself at a low location. It needs to get colder is the bottom line. A lingering persistent slab is allowing for "Whumphing" like I've never heard/seen before. Don't get "a fear of missing out" it is safer to stay away!

Avalanche Character 1: 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.

A layer of buried facets still exists above 9250' elevation within the snowpack. At 42cm (23.6") below the surface a 10cm (4") thick layer of unconsolidated snow grains exist that have shown to be reactive in tests with light to moderate pressures. This weak layer has had an additional stress added to it from new snow accumulations & rain. The weight & lubrication combined with temperatures above freezing, may cause this layer to fail under the weight of a human. Very apparent whumphing, or collapsing of air spaces, while traveling across flat land should alarm you. Apply that collapsing mechanism to a steeper slope & you got an avalanche.

Avalanche Character 2: Wet Slab
Wet Slab avalanches occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoid avalanche terrain when you see pinwheels, roller balls, loose wet avalanches, or during rain-on-snow events.

One slide-path above Leavitt Rd that is a known "Repeat Offender" faces East & always collects wind deposits. Yesterdays rain likely compromised the shear resistance of a newly deposited wind slab & saturated it to the point of failure. Shearing occurs from added stresses to the pack & often tears away the snowpack vertically as it propagates horizontally on a layer of weakness. This is a very destructive form of avalanche because of the heavy mass & surface area potential it has when propagated across a starting zone.

Avalanche Character 3: 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.

Many of the slopes steeper than 35 degrees had wet loose avalanches due to rain. The rain saturation of the new snows was visible & became progressively thinner at you ascend. Rain will increase the density of the new snow & only percolates so far before capillary action takes over. The saturated snow sits atop a fluffier, less dense snow & wants to pull itself away somewhat uniformly. We call them roller balls or cinnamon rolls. As a snowmobiler we can notice ribbons shooting off our skis & a track pattern that's unique.

Snowpack Discussion

More rain fell higher than initial expectations. Our weather forecast seemed to be getting warmer & wetter every time you'd check. It was noted that surface saturation of the snow was happening with the appearance of roller balls, loose wet & wet slab avalanches. The snowpack starting at 8500' is almost nonexistent. The depth exponentially grows as you near 9500' within a small distance traveled. Please refer to my Snow Pilot graph for further explanation. We still see a persistent slab problem 42cm below the surface @ 9500'. Rain may help dissolve this hazard below 9000' but where it remained neutrally cold & dry we are still seeing reactivity.

recent observations

Many Loose Wet avalanches have been observed above & around treeline. One R2D2 Wet Slab avalanche occurred to the NW of Leavitt Lake Rd. Visibility was poor for seeing much else.


Rain fell very high on the landscape. Very little wind was observed during precipitation. The BWRA saw a wet mix of snow & fog, making me feel like I was in Alaska again. Temps struggle to fall below freezing at our weather stations.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Mostly cloudy with isolated snow showers Partly cloudy then clearing Partly cloudy then mostly cloudy
Temperatures: 41 - 47 deg. F. 25 - 30 deg. F. 45 - 53 deg. F.
Wind direction: West West then light winds Light winds becoming west
Wind speed: 15 to 25 mph; gusts to 45 mph 10 to 15 mph; gusts to 40 mph Light then 10 to 15 mph in the afternoon; gusts to 40 mph
Expected snowfall: 0 in. 0 in. 0 in.
For above 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Mostly cloudy with scattered snow showers Partly cloudy then clearing Partly cloudy then becoming mostly cloudy
Temperatures: 34 - 39 deg. F. 22 - 27 deg. F. 38 - 44 deg. F.
Wind direction: West Northwest West
Wind speed: 25 to 40 mph; gusts to 60 mph 20 to 35; gusts 50 decreasing to 40 mph 20 to 30 mph; gusts 40 increasing to 50 mph
Expected snowfall: 0 in. 0 in. 0 in.

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.