Snowpack Summary published on March 19, 2018 @ 9:52 am
Issued by Ryan Lewthwaite -

bottom line:

The riding has been excellent with abundant fresh snow to be had by all. The stability is rising with the new snow just in time for a rapid warm-up & another blast of moisture invites itself to the BWRA. Todays sunshine & temps will allow for loose wet & cornice fall avalanche activity, especially in the afternoon hours. Isolated wind slabs are in the landscape on leeward aspects (NW-N-E) & should be treated with respect.

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.

Warm temperatures & intense solar radiation will keep us on our toes for the next two days. The upcoming spring equinox will bring us longer daylight hours as the arc of the sun will progress higher in the sky. Aspects that get more direct sun will have a greater chance of avalanche activity & warm ambient temps can loosen snow on North facing slopes as well. Look for diurnal refreezes at night with afternoon spring conditions.

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.

Cornices are quite large in the BWRA & will be shedding themselves during afternoon warm-ups. Whether below or on top of a ridgeline be cautious of falling cornices, they can entrain much more snow than anticipated. A cornice by itself can weigh tons, when it falls the mass can trigger & even step-down into older weak layers on slopes increasing the destructive potential.

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.

The strong winds associated with the last two storms has transported snow to places & stiffened the snowpack in others. The slabs are becoming more stable & even stubborn to initiate failures, but in the right spot there is still a likelihood of triggering. In the alpine & near treeline these slabs are most prominent on NW-N-E aspects.

Snowpack Discussion

With the strong SW winds we are able to find larger drifts & cornices on leeward N-NE aspects. Wind scabbing, surface hoar & loose dry snow can be observed on more shaded areas. The snowpack is growing in March to keep us on our sleds a little longer. Use this time to hone your backcountry skills, we are here to help. Ask your riding partners to check the forecast & make informed group decisions together.

recent observations

We have seen an avalanche cycle for the past few days as things begin to stabilize in the mountains. People are mostly avoiding areas with recent avalanche activity. The signs of mid-storm avalanches are even hard to detect in areas where blowing snow has covered any crown remnants. Yesterday we noticed a large debris pile from the "Repeat Offender" above Leavitt Rd. The avalanche stopped just shy of the road but traveled a good 1000' feet, its crown was unnoticeable.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 21 deg. F.
Max. temperature in the last 24 hours: 31 deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours: mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 63 inches

A quick shot of sun & warm temperatures today into tomorrow with light winds expected. Near mid 40F degrees tomorrow will start the next round of precipitation for Mono County. An AR (atmospheric river) event is in store for Wed-Thu with continuing snow showers through the weekend. Initial rain showers at higher elevations will transition to moderate snow showers as the trend cools.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Monday Monday Night Tuesday
Weather: Mostly sunny. Partly cloudy with increasing clouds. Mostly cloudy with a chance of snow & possible rain to 7500'
Temperatures: 36 to 42 deg. F. 20 to 25 deg. F. 40 to 46 deg. F.
Wind direction: Light winds Light winds South
Wind speed: Light winds Light winds with gusts to 30 mph late. 10 to 15 mph; gusts to 30 mph
Expected snowfall: 0 in. 0 in. 1 in.
For above 10000 ft.
  Monday Monday Night Tuesday
Weather: Mostly sunny Partly cloudy with increasing clouds. Mostly cloudy with snow showers & possible rain in the afternoon.
Temperatures: 29 to 34 deg. F. 20 to 26 deg. F. 33 to 38 deg. F.
Wind direction: Light winds South Southwest
Wind speed: Light winds 15 to 20 mph; gusts to 35 mph increasing 20 to 30 mph; gusts to 45 mph late 20 to 30 mph; gusts to 45 mph
Expected snowfall: 0 in. 0 in. 2 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.