Avalanche Advisory: Wednesday - Mar 27, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 28, 2019 @ 6:53 am
Avalanche Advisory published on March 27, 2019 @ 6:53 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

The avalanche danger will rise to HIGH at Upper/Mid elevations. CONSIDERABLE hazard will exist at Lower elevations. WIND SLAB avalanches both natural and human triggered will be very likely on N-E ASPECTS due to extreme SW winds and significant new snowfall (10-24”). Fresh STORM SLAB will also be a concern on all aspects at Mid/Lower elevations. Travel in avalanche terrain is not recommended.

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Prevailing SOUTHERLY winds combined with anticipated large snowfall amounts will load NORTHERLY-EASTERLY slopes throughout the forecast zone today.  Southerly winds will dramatically load alpine start zones and extreme gusts will redistribute snow in dynamic and unpredictable ways at mid to low elevations. Actively loading areas (leeward cirques, gullies, cornice lines and catchment areas) should be avoided as they will be sensitive to a variety of both human and natural triggers. New wind slab will be forming not only on a variety of firm wind shorn surfaces, but on top of already sensitive existing wind slabs that have been quite reactive recently throughout the range on a variety of aspects. Avoiding slopes over 30degrees today or any terrain that is exposed from above is recommended as avalanche danger may quickly escalate with new snowfall and loading wind.

Avalanche Problem 2: Storm Slab
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If snowfall totals end up on the high end of predictions, we could very well see upwards of 2ft, perhaps more, of new snow that will be falling on a variety of old snow surfaces. Smooth wind board, melt-freeze crusts, and colder areas of the snowpack that have seen some near-surface faceting (loose decomposition) exist throughout the forecast zone. Although the warmer temperatures during this storm should promote bonding, the freshly fallen snow will be sensitive inititally and need time to stabilize. It will be a good day to either make soup or not travel in avalanche terrain. Staying off slopes above 30degrees in angle and avoiding terrain traps and exposed terrain are recommended. Pay attention to collapsing or audible whumpfing of the snow, shooting cracks and natural avalanche activity

 

advisory discussion

There have been multiple reported skier triggered avalanches over the past 5 days where backcountry travellers have triggered wind slabs in steep confined terrain, open slopes and from below while ascending convex wind loaded slopes. These human triggered slides have been large enough to carry a person down slope and even bury them in some cases (D2 scale). These conditons are now going to be buried by the next onslaught of wind driven deposition and slab development. It will be good to keep a keen eye on what transpires over the course of the next few days and be on our toes for dangerous avalanche conditions.

recent observations
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3/26 – Rock Creek – Hilton Lks Area –Skier triggered D2 avalanche

3/26 – Mammoth Area – Sherwins – Windy, mid slope snow deposition

3/26 – Mammoth Area –TJ Bowl – Avalanche activity

3/26 – Mammoth Area – Red Cone/Hollywood chute – snow conditions

3/24– Bridgeport Area – Kettle Peak –Skier triggered avalanche

3/24 – Big Pine Area/Birch Lake–“The Thumb” – Skier triggered avalanche

3/23 – Lee Vining – Ripper Chute – Skier triggered avalanche/partial burial

 

Weather and CURRENT CONDITIONS
weather summary

Cloudy conditions and snow for today. Snow is slated to start falling around dawn this morning with the heaviest rates predicted during the day Wednesday. 10-20” is predicted for today through tonight below 10000ft, with higher amounts of up to 24” in the high country into Thursday morning. SW winds will prevail with moderate to strong velocities of 20-35mph below 10000ft with speeds of 35-55mph in the higher elevations. Gusts will be extreme in the 70-85mph range. Temperatures will still reach above freezing ~37F at lower elevations while 20-30F will keep things cool up high, especially with the wind chill.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow. Snow levels 7000 feet. Chance of precipitation is 90%. Cloudy then becoming partly cloudy. Snow showers in the evening, then chance of snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 90%. Partly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 30%.
Temperatures: 29 to 37. deg. F. 16 to 24. deg. F. 25 to 35. deg. F.
Mid Slope Winds: Southwest 20 to 35 mph with gusts to 70 mph. Southwest 15 to 30 mph with gusts to 60 mph. Southwest 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 90% probability of 7 to 13 inches. 10% probability of 13 to 16 inches. | SWE = up to 0.70 inch. in. 90% probability of 3 to 9 inches. 10% probability of 1 to 3 inches. | SWE = 0.20-0.45 inch. in. Up to 1 inch. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow. Snow levels 7000 feet. Chance of precipitation is 100%. Mostly cloudy. Snow showers in the evening, then chance of snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 100%. Partly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 35%.
Temperatures: 20 to 30. deg. F. 12 to 17. deg. F. 17 to 27. deg. F.
Ridge Top Winds: Southwest 35 to 55 mph with gusts to 85 mph. Southwest 30 to 50 mph decreasing to 30 to 40 mph after midnight. Gusts up to 70 mph. Southwest 20 to 35 mph with gusts to 55 mph.
Expected snowfall: 80% probability of 7 to 14 inches. 20% probability of 14 to 18 inches. | SWE = 0.55-0.80 inch. in. 90% probability of 4 to 10 inches. 10% probability of 2 to 4 inches. | SWE = 0.30-0.55 inch. in. Up to 1 inch. | SWE = less than 0.10 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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