THIS SNOWPACK SUMMARY EXPIRED ON March 2, 2018 @ 9:59 am
Snowpack Summary published on February 28, 2018 @ 9:59 am
Issued by Ryan Lewthwaite -

bottom line:

BWRA Snowmobiling CLOSED (for now). We are anticipating a very large winter storm for the next 3 days. Atmospheric River events like we saw many times last season are moisture rich with a steep pressure gradient, meaning high winds. If the storm cooperates with the forecasts expect a reopening of the BWRA for Monday, we are hoping. Please heed travel warnings as avalanche danger could reach HIGH potential with this new snow & wind. We are here to keep you informed of the danger. Sharpen your backcountry skills & wait for the appropriate time to get out a enjoy.

Avalanche Character 1: 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.

The forecast says we can expect a large amount of snow with the upcoming AR (atmospheric river) event. Thursday through Saturday we could experience a dramatic rise in avalanche danger from this storm in the form of storm slabs. Avoiding avalanche terrain is the best preventative measure.

Avalanche Character 2: Loose Dry
Loose Dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.

6-7 natural loose dry avalanches were seen on the 27th with only 3" of new snow. With new snow on the way loose dry avalanches will be happening, whether you like it or not. Slopes over 35 degrees in steepness are to be avoided.

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.

There is a high probability that we will get extreme (gale) force winds with this storm. The potential of 100 mph winds & lots of available new snow for transport will create harder wind slabs & cast them low on slopes. Expect scouring above treeline & deposition at & below treeline. Slabs will be thick, the question is how will they react with the weight of a recreationist.

Snowpack Discussion

Shallow snowpack overall still exists in the BWRA. A thin snowpack, more continental, has numerous issues associated with it. Snow, especially thin layered, does not like rapid change over space & time & is more susceptible to having a poor structure than a thick snowpack. The layers of our current snowpack are riddled with unconsolidated facets & solid icy crusts. Yesterday failures below the uppermost crust were showing results at 15cm deep with strong to moderate forces. The addition of new snow & weight to such a structure will create instabilities in the form of large avalanches.

recent observations

A natural R2D1 storm slab avalanche was seen above Big Easy Bowl. Around 6-7 natural loose dry avalanches were observed on all aspects above treeline, relatively small in size.

CURRENT CONDITIONS Weather observations from Sonora Pass
0600 temperature: 10 deg. F.
Max. temperature in the last 24 hours: 26 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: 1 inches
Total snow depth: 19.7 inches
weather

~2.5" (6.4cm) new was observed at our intermittent stormboard near the Sonora Pass Snotel site on the morning of 2/27. Very low density snow fell with almost no wind, weird huh.. Was a chilly morning with patchy low-lying cloudy. Any slight breeze or exposure to the sun & the new snow was destroyed or transported. We are anticipating a strong Atmospheric River event with large amounts of snow forecasted through Saturday, hold on.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8000 ft. to 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Partly cloudy with increasing clouds Mostly cloudy with snow increasing late Mostly cloudy with snow
Temperatures: 31 - 37 deg. F. 18 - 23 deg. F. 28 - 34 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 10 to 15 mph; gusts to 25 mph 15 to 20 mph; gusts to 40 mph increasing 20 to 30 mph; gusts to 70 mph late 20 to 35 mph; gusts to 75 mph increasing 30 to 45 mph; gusts to 90 mph later
Expected snowfall: 0 in. 2 in. 5 to 11 in.
For above 10000 ft.
  Wednesday Wednesday Night Thursday
Weather: Partly cloudy with increasing clouds. Chance of snow later Mostly cloudy with snow increasing overnight Cloudy with snow
Temperatures: 24 - 29 deg. F. 14 - 19 deg. F. 21 - 26 deg. F.
Wind direction: West Southwest Southwest
Wind speed: 15 to 20 mph; gusts to 25 mph increasing to 35 mph gusts 20 to 30 mph; gusts to 50 mph increasing 40 to 55 mph; gusts to 80 mph late 45 to 65 mph, gusts to 100 mph!
Expected snowfall: 0 in. 2 in. 5 to 11 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.