Snowpack Summary published on March 29, 2019 @ 7:51 am
Issued by Ryan Lewthwaite -

bottom line:

The new 25cm (10") of snow has been deposited into Wind Slabs on all aspects & elevation zones. Loose Wet avalanches could be seen in below treeline areas or on slopes that get uninhibited sun in the afternoon. Preparation for Caltrans cutting out Hwy 108 has begun, act accordingly.

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.

Swirling winds have helped create shallow Wind Slabs on all aspects & elevation bands. The newly deposited 25cm (10") rests above a firm windpacked layer that could act as the interface for avalanches to occur on. Test results ellude to the possibility of fracture at the bottom of the new snow layer with moderate forces. Buffed-out or billowing surface snow conditions can help you find where the wind has transported yesterdays new snow to Slabs.

Avalanche Character 2: 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.

You are likely to see Loose Wet avalanche activity in the below treeline areas & on slopes that gain prolonged direct sunshine. Higher in the mountains temperatures will remain near freezing, but sun effect could bring this avalanche problem into fruition.

Snowpack Discussion

The new snow from yesterday has been blown around by wind creating Wind Slabs on all aspects & elevations. Todays sun & warmth will improve the Wind Slab issue in areas below treeline. Conversely near & above treeline zones will hold onto the Wind Slab problem for a longer duration. Loose Wet avalanche activity may be seen on sunny slopes below treeline in the afternoon hours. Instability tests done were revealing a firm windpacked layer below the new 25cm (10') of snow as a problematic interface. Moderate forces could initiate a fracture at or above this interface buried 20-30cm deep. Test results showing likely propagation propensity was not confirmed.

recent observations

~3/28 Moments of S1 Graupel & Rime were observed in the mid-afternoon rolling down slopes & collecting. 25cm of new snow was measured in the last 24 hours. Creeks are re-emerging everywhere.

~3/27 Light snow & Strong swirling winds were observed transporting snow across the landscape. Patchy clouds & intermittent sun.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 18 deg. F.
Max. temperature in the last 24 hours: 33 deg. F.
Average wind direction during the last 24 hours: Northwest
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: 0 inches
Total snow depth: 102 inches

We can expect sun & light winds throughout the weekend. Overnight temperatures will remain cold & will help the snowpack refreeze. No precipitation is slated for the next two days. Low elevations will see warm temperatures but in the alpine we will hover around freezing. Next week will be active with precipitation & an Atmospheric River could make landfall impacting our area Thursday. Rain on snow should be expected.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Friday Friday Night Saturday
Weather: Sunny. Patchy clouds. Sunny.
Temperatures: 32 to 42 deg. F. 14 to 19 deg. F. 33 to 41 deg. F.
Wind direction: Southwest West Light winds
Wind speed: 5 to 10 mph 10 mph becoming light Light winds
Expected snowfall: 0 in. 0 in. 0 in.
For above 10000 ft.
  Friday Friday Night Saturday
Weather: Sunny. Patchy clouds. Sunny
Temperatures: 23 to 31 deg. F. 8 to 13 deg. F. 26 to 32 deg. F.
Wind direction: Southwest West Light winds
Wind speed: 5 to 10 mph 10 mph becoming light Light winds
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.