THIS SNOWPACK SUMMARY EXPIRED ON April 26, 2017 @ 11:32 am
Snowpack Summary published on April 23, 2017 @ 11:32 am
Issued by Ryan Lewthwaite -

bottom line:

Warmth & Winds will dominate the atmosphere for the next few days. An abundance of daily sun & overnight temperatures above freezing will keep our snowpack in constant motion & melting. Loose-Wet Avalanches & Cornice Failure will be the avalanche concerns for our BWRA. All aspects above & below treeline have had these types of avalanche activity & the rate can vary with time of day & the suns angle on the landscape. Mid-week we saw human triggered Wind-Slabs popping after we received 3-18" of Sierra cement on North through Northeast aspects, which could still be a concern. A possible future avalanche problem may result from a snow-metamorphic process known as Radiation-Recrystallization which is happening in the surface 10cm. Solar radiation has effected the snow by faceting the thinnest surface layer & melting the underlying grains into a slush. If we receive more snow or drastic freezing this buried layer will give us a heightened avalanche issue.

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.

All aspects, above & below treeline, have had recent Loose-Wet Avalanche activity. Southerly aspects definitely have had the majority of this type of avalanches but nights without freezing have loosened the uppermost portion of the snowpack across the BWRA. Radiation Recrystallization has occurred on many slopes & could prove to be a catalyst for future avalanches if we receive more precipitation.

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.

Cornice Falls have proven to be a considerable contributor to the avalanche problem lately. The moderate to strong winds we've had in the BWRA has created a landscape dominated by wind-scouring & snow deposition. Melting & movement of cornices has allowed Loose-Wet, Loose-Dry, & Wind-Slab avalanches to release themselves in quantity & localized in Terrain Traps.

Snowpack Discussion

Our deep snowpack is melting quickly from the top down. Surface faceting & Radiation-Recrystallization is occurring and may prove to be a future avalanche hazard. New snow we received Monday & Tuesday had formed wind-slabs & grew cornices in mass. Since Wednesday the new snow has been actively shedding itself in a variety of ways including: Loose-Wet, Loose-Dry, Wind-Slab, & Cornice-Fall.

weather

Weak low pressure will bring breezy conditions today with light showers possible towards the Oregon border. Monday through Wednesday, additional systems will keep breezy conditions going with light shower chances spreading farther south. Drier weather will return late in the week. Temperatures near average today will fall to slightly below average this week.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Sunday Sunday Night Monday
Weather: Partly cloudy then becoming sunny Partly cloudy Mostly cloudy. Scattered snow showers in the morning. Isolated snow showers in the afternoon
Temperatures: 46-54 deg. F. 31-36 deg. F. 39-49 deg. F.
Wind direction: Southwest West West
Wind speed: 10 to 20 mph Gusts up to 40 mph 10 to 15 mph with gusts to 35 mph 15 to 25 mph. Gusts up to 40 mph increasing to 55 mph in the afternoon
Expected snowfall: 0 in. 0 in. little to none in.
For above 10000 ft.
  Sunday Sunday Night Monday
Weather: Partly cloudy then becoming sunny Clear then becoming partly cloudy Mostly cloudy. Isolated snow showers
Temperatures: 36-44 deg. F. 26-32 deg. F. 29-37 deg. F.
Wind direction: Southwest West West
Wind speed: 25 to 45 mph with gusts to 60 mph decreasing to 20 to 30 mph with gusts to 50 mph in the afternoon. 15 to 25 mph with gusts to 40 mph 30 to 40 mph with gusts to 65 mph increasing to 30 to 50 mph with gusts to 85 mph in the afternoon
Expected snowfall: 0 in. 0 in. little to none 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.