THIS SNOWPACK SUMMARY EXPIRED ON March 29, 2019 @ 8:33 am
Snowpack Summary published on March 27, 2019 @ 8:33 am
Issued by Ryan Lewthwaite -

bottom line:

An incoming spring storm could rapidly increase the avalanche hazard this afternoon. With fluctuating snow levels, 1 to 2 feet of accumulation, & strong SW winds we are looking at a dynamic set of avalanche problems. Utilize low consequence terrain & surface snowpack evaluations to determine if your riding area contains these variables.

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.

Rapid accumulations this afternoon will be effected by Strong Southwest winds that could gust to 85 mph! Keep in mind that Wind Slabs could have nearly 5 times the amount of wind blown snow as falling storm totals. Near & below treeline slopes will have the largest deposits that could be reactive to fracture initiation & propagation.

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.

In wind protected areas above 7000' falling snow will collect on an unsupportable crust, that may not have refrozen overnight. Use shallow pit tests to determine if there is good bonding between the old snow & new snow interface. If it is raining on the Storm Slab use the terrain to avoid being caught in Loose Wet or Wet Slab avalanches.

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.

Warm overnight temperatures & the liklihood of rain on snow could cause this type of avalanche problem in below treeline zones. With enough rain on snow we could be looking at a more dangerous Wet Slab issue. Take notice of where you see rain changing to snow & investigate the saturation.

Snowpack Discussion

The firm windpacked snow surface in areas above treeline is not desirable for riding. However, on shaded near & below treeline slopes the snow is soft & wet in areas due to a shallow refreeze overnight. Rapid accumulations today will make for Considerable to High avalanche danger across the mountains. With enough low elevation rain we could see Loose Wet or even Wet Slab avalanches in areas near & below 7000'. Wind Slabs will grow exponentially with Southwest winds that could gust to 85 mph!

recent observations

~3/26 observations found strong SW winds with little to no snow transport. Loose wet avalanches were entraining the surface snow to a depth of 10cm. The scoured alpine zone is firmly windpacked with little soft accumulations.

~3/24 Several D1 Loose Wet & Wind Slab avalanches were observed within the newly transported snow. Rapid warming added to the breakdown of snow grains & temperature inversions allowed for continuous melting.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 29 deg. F.
Max. temperature in the last 24 hours: 40 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: Moderate mph
Maximum wind gust in the last 24 hours: Strong mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: 96 inches
weather

Strong Southwest winds have begun to pick-up with the arrival of todays Pacific storm. We are anticipating snowfall amounts above 7000' to range from 1 to 2 feet by Thursday afternoon. A very superficial refreeze occured in the mountains overnight, with Sonora Snotel reaching 30F at 5AM. Initially we could see a rain/sleet mixture to elevations near 7000', with possible thunder. The majority of the snowfall will be deposited this afternoon into tonight with low visibility from blowing snow.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Cloudy with low elevation rain & snow showers above 7000'. Snow Level Around 7000' Decreasing clouds with diminishing snow showers late. Snow Level Below 7000' Partly cloudy with a chance for snow showers. Snow Level Below 7000'
Temperatures: 29 to 37 deg. F. 16 to 24 deg. F. 25 to 35 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 20 to 35 mph; gusts to 70 mph 15 to 30 mph; gusts to 60 mph 15 to 25 mph; gusts to 45 mph
Expected snowfall: 7 to 13 in. 3 to 9 in. 1 in.
For above 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Cloudy with low elevation rain; & snow showers above 7000'. Snow Level Around 7000' Decreasing clouds with diminishing snow showers late. Snow Level Below 7000' Partly cloudy with a chance for snow showers. Snow Level Below 7000'
Temperatures: 20 to 30 deg. F. 12 to 17 deg. F. 17 to 27 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 35 to 55 mph; gusts to 85 mph 30 to 50 mph; gusts to 70 mph 20 to 35 mph; gusts to 55 mph
Expected snowfall: 7 to 14 in. 4 to 10 in. 1 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.