THIS SNOWPACK SUMMARY EXPIRED ON February 11, 2019 @ 7:27 am
Snowpack Summary published on February 9, 2019 @ 7:27 am
Issued by Ryan Lewthwaite -

bottom line:

It appears as the snow faucet has been turned on again. The arrival of yet another significant storm with estimates over 4' of new snow for the Sonora Pass zone will increase the avalanche danger. This afternoon the mountains will unleash Heavy Snow & Gale Force Winds above 7000' & will continue through the weekend. Expect Hazardous conditions as wind driven snow will collect in areas previously loaded by prevailing Southwesterlies.

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.

Continued Southwest flow will exponentially load areas that are not scoured by Gale force winds. Near & Below Treeline are the suspect areas for large deposits of wind transported snow, especially on aspects NW-N-E-SE. Whiteout conditions this afternoon with the rumor of gusts over 100 mph are forecasted!

Avalanche Character 2: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

We gained 2-6" lastnight with the expectation that another 4' could accumulate by Monday morn. Low density powder snow conditions are really fun in NO Consequence areas, but on slopes over 30 degrees be Warned! Search for the areas both effected by Storm & Wind Slabs as they could be dangerous to enter with your riding group.

Avalanche Character 3: 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.

Since the retreat of the most recent storm activity we have noticed Very Large Cornice formations. These unsupported masses hang above some High Consequence terrain & their failure could step into the already present Slabs below the surface snow. Whether above or below you the risk of traveling around these objects is unnecessary.

Snowpack Discussion

The snowpacks stability will rapidly decrease today with the arrival of a strong cold front. The +66" that has been enjoyable for getting stuck/ unstuck has set-up surprising well & even supportable in places. Surface wind & sun effected slopes are somewhat firm in the above treeline zones & will continue this theme throughout this storm system as winds could gust over 100 mph! Expect very pronounced wind slabs to keep growing & becoming very dangerous to riders. The size & mass of overhanging Cornices should be an alarm to the potential hazard they possess. 

recent observations

~ Wind Slab avalanches have been observed on N-E aspects with activity decreasing yesterday

~Cornices are growing with Gale SW winds & loading, avoid these wind features at all costs

~Loose Dry avalanches have been seen below trees where falling snow is the trigger

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 18 deg. F.
Max. temperature in the last 24 hours: 25 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: 4 inches
Total snow depth: 88 inches

A weak cold front will aboandon us this morning while a stronger cold front rushes in behind. We will not see the break in weather that other areas will experience this afternoon, just snow. The system entering the Sierra Crest today will bring with it Gale force winds & Heavy rates of snowfall through the weekend. There is much confidence that we will see blowing snow & whiteout conditions that can cause severe travel impacts. Southwest winds will transport snow to already loaded slopes allowing avalanche activity to to increase.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Saturday Saturday Night Sunday
Weather: Cloudy with snow. Snow Level Below 7000' Cloudy with snow. Snow Level Below 7000' Cloudy with snow. Snow Level Below 7000'
Temperatures: 20 to 28 deg. F. 14 to 20 deg. F. 15 to 23 deg. F.
Wind direction: Southwest South Southwest
Wind speed: 15 to 30 mph; gusts to 55 mph 20 to 35 mph; gusts to 80 mph 15 to 30 mph; gusts to 65 mph decreasing to 40 mph gusts later
Expected snowfall: 2 to 5 in. 6 to 12 in. 4 to 10 in.
For above 10000 ft.
  Saturday Saturday Night Sunday
Weather: Cloudy with snow. Snow Level Below 7000' Cloudy with snow. Snow Level Below 7000' Cloudy with snow. Snow Level Below 7000'
Temperatures: 12 to 18 deg. F. 4 to 12 deg. F. 8 to 13 deg. F.
Wind direction: Southwest Southwest Southwest becoming West
Wind speed: 30 to 45 mph; gusts to 65 mph 35 to 55 mph increasing to 45 to 65 mph late; gusts to 105 mph! 50 to 65 mph; gusts to 100 mph, later decreasing to 25 to 35 mph; gusts to 60 mph
Expected snowfall: 2 to 6 in. 8 to 15 in. 5 to 11 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.