Avalanche Advisory: Saturday - Mar 9, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 10, 2019 @ 7:15 am
Avalanche Advisory published on March 9, 2019 @ 6:15 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

The avalanche danger is MODERATE at Upper elevations and LOW at Middle and Lower elevations. Southerly winds will continue to transport freshly fallen snow and stiffen and redistribute residing dry snow to form WIND SLAB on leeward Northerly-Easterly aspects. Steep and confined terrain in leeward catchment zones are of most concern.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Leeward NORTHERLY-EASTERLY slopes will be areas most likely for a skier to trigger a wind slab avalanche. Prevailing SOUTHERLY WINDS will continue at velocities of 15-30mph which are ideal for transporting available snow to leeward aspects. Catchment zones such as concave alpine cirques, couloirs, gullies, and extreme terrain will be likely features to load with wind transported snow. Be aware of active wind loading and fresh looking snow deposits on terrain you are travelling upon. Simply probing the snow can also give you clues on how deep or robust existing buried layers such as the 2/14 rain crust and old existing bed surfaces are within the snowpack. Pay attention for drummy or hollow sounding pieces of snow and an upside down feeling snowpack, such as hard, denser snow existing on top of softer, less cohesive snow. Continue to analyze and re-evaluate conditions as you progress upward on slope.

 

Avalanche Problem 2: Cornice
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Avoid cornices which have been building primarily on EASTERLY and NORTHERLY aspects throughout the range. Give these curling wavelike features a wide berth and make sure you are well on terra firma on the windward side of ridges. Cornice fall not only is hazardous if it gives way beneath you, but can affect travelers on slopes below. Cornice fall can be the big trigger that starts avalanches on slopes below as the falling blocks can be of tremendous weight and scale. Cold temps and forecasted cloudy skies should keep these relatively locked up today, but if sunnier conditions prevail, be aware that solar gain could contribute to loosening freshly formed cornices.

 

advisory discussion

From yesterday’s reports, sounds like the new snow from this week got severely wind-affected in exposed alpine areas with hardening wind slab, cornice development, and overall firm and breakable conditions. Sheltered tree skiing on the other hand remains a good soft option and also a safer alternative than dealing with potential wind slab and surface conditions not at all favorable to preserving the knees right now. Goes to show just how quickly surface conditions can change overnight, each day brings something new in the mountains.

Weather and CURRENT CONDITIONS
weather summary

Colder temperatures today with mostly cloudy to partly cloudy skies. The south end of the forecast zone may see sunnier conditions. SW winds continue at moderate speeds in the 15-25mph range with slightly stronger velocities and locally higher gusts up to 45mph at ridge tops. A chance of snow with up to 1” may fall in the Mammoth area. Temperatures remain cool at 24-32F in the lower elevations while high elevations will be in the 16-22F range today. Small accumulations of snow are forecast for the area for the next several days with the greatest potential on Sunday for 1-3”.

 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming mostly cloudy. Chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%. Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 30%. Cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 70%.
Temperatures: 24 to 32. deg. F. 11 to 17. deg. F. 21 to 29. deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 35 mph. Southwest around 15 mph with gusts to 25 mph in the evening becoming light. Light winds.
Expected snowfall: 100% probability up to 1 inch. | SWE = trace amounts. in. 70% probability up to 1 inch. 30% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in. 70% probability of 1 to 4 inches. 30% probability up to 1 inch. | SWE = up to 0.20 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming mostly cloudy. Slight chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 20%. Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 35%. Cloudy. Chance of showers. Snow levels below 7000 feet. Chance of precipitation is 75%.
Temperatures: 16 to 22. deg. F. 5 to 10. deg. F. 14 to 20. deg. F.
Ridge Top Winds: Southwest 15 to 30 mph with gusts to 45 mph. Southwest around 15 mph with gusts to 25 mph. Light winds.
Expected snowfall: 100% probability up to 1 inch. | SWE = trace amounts. in. 70% probability up to 1 inch. 30% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in. 70% probability of 2 to 4 inches. 30% probability up to 2 inches. | SWE = up to 0.20 inch. in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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