Avalanche Advisory: Saturday - Feb 9, 2019

THIS AVALANCHE ADVISORY EXPIRED ON February 10, 2019 @ 6:40 am
Avalanche Advisory published on February 9, 2019 @ 6:40 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

The avalanche danger is HIGH at upper elevations. Freshly developed WIND SLAB on Northerly aspects will be the primary concern.

CONSIDERABLE danger will exist for mid elevations with MODERATE avalanche danger at lower elevations today. New DRY LOOSE and STORM SLAB avalanches will also present hazards.

 

4. High

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

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Moderate to strong Southerly winds combined with over a foot of low-density easily transportable snow, have built wind slabs overnight and will continue to load leeward aspects throughout the day. NORTHERLY ASPECTS are the main concern, but look for cross-loading on more oblique aspects to the wind (Westerly and Easterly).

Look for recent avalanche activity, new cornice growth and fat looking wind pillows, and uneven snow deposits near and adjacent to ridgeline, crossloaded gullies, and convex rolls. Low visibility today combined with very dangerous avalanche conditions will make travel in the Upper elevations not recommended. 

Avalanche Problem 2: Loose Dry
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Cold temperatures, moderate to strong loading winds, and over a foot of lower density snow will make loose dry avalanches very likely on nearly all aspects. These point release avalanches may start small, but with the significant volume of freshly fallen snow blanketing the mountains, these avalanches could very well entrain a large amount of snow, may trigger other residing wind and storm instabilities, and can produce significant debris piles-- especially in terrain traps such as depressions and gullies. Good route finding both up and down is imperative to minimize your exposure to these avalanches. Pay particular attention to complex and steep terrain where even small amounts of snow falling from cliff faces or crags may start a loose dry avalanche. Steep terrain, even in lower elevations and within trees, will need to be treated with care as starting "sluffs" and small slides could take you for a ride into places you don't want to end up.

Avalanche Problem 3: Storm Slab
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There was approximately 1" of SWE (Snow Water Equivalent) in 14" of snow this morning at 9000ft at Mammoth Mountain. Although temperatures remain cold this morning in the teens, this amount of low density snow will begin to settle, be affected by atmospheric and surface winds, and could start to form more cohesive slabs that will be sensitive today. Treat all terrain with respect and be on the lookout for RED FLAGS such as shooting cracks, recent avalanche activity and any whumpfing of the snowpack.

advisory discussion

Snow conditions could be quite amazing in areas providing for good common sense travel practices. With limited visibility and increasing winds, be very aware of what is above and around you today. Play it safe and have fun.

SKIING WITH A BUDDY is  highly recommended in regards to deep snow immersion. This weekends huge storm combined with last nights additional snowfall will make for deep conditions today. Falling headfirst into a tree well right now could be very hazardous. Travel with a partner who could help you get out, but if alone, try not to panic, try to maintain a good airway to breath, and slowly dig yourself out in a planned concerted effort.

Weather and CURRENT CONDITIONS
weather summary

Over a foot of snow (16") has fallen in the Mammoth area overnight and more snow is in the forecast for today (2-5”) through tonight (5-15”) and continuing Sunday. Cloudy conditions and cold temperatures will prevail. These cold temperatures (12-18F above 10000ft and in the 20sF lower elev) will make for blower snow conditions but also hazardous wind chill. Be prepared today with the warm kit and something to protect the face. Moderate to Strong Southerly winds will continue to blow throughout today and ramp up with gusts expected in the 100mph range tonight. Another 6-12” of snow is expected for Sunday.

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: Cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 70%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 90%. Cloudy. Snow in the morning, then snow likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 95%.
Temperatures: 20 to 28. deg. F. 14 to 20. deg. F. 15 to 23. deg. F.
Mid Slope Winds: Southwest 15 to 30 mph with gusts to 55 mph. South 20 to 35 mph with gusts to 80 mph. Southwest 15 to 30 mph. Gusts up to 65 mph decreasing to 40 mph in the afternoon.
Expected snowfall: 70% probability of 2 to 5 inches. 30% probability of 5 to 10 inches. | SWE = up to 0.25 inch. in. 90% probability of 6 to 12 inches. 10% probability of 12 to 20 inches. | SWE = 0.30 to 0.60 inch. in. 90% probability of 4 to 10 inches. 10% probability up to 4 inches. | SWE = 0.25-0.50 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Cloudy. Snow in the morning, then snow likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 80%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow in the morning, then snow likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 95%.
Temperatures: 12 to 18. deg. F. 4 to 12. deg. F. 8 to 13. deg. F.
Ridge Top Winds: Southwest 30 to 45 mph with gusts to 65 mph. Southwest 35 to 55 mph increasing to 45 to 65 mph after midnight. Gusts up to 105 mph. Southwest 50 to 65 mph with gusts to 100 mph becoming west and decreasing to 25 to 35 mph with gusts to 60 mph in the afternoon.
Expected snowfall: 80% probability of 2 to 6 inches. 20% probability of 6 to 10 inches. | SWE = 0.15-0.25 inch. in. 80% probability of 8 to 15 inches. 20% probability of 15 to 25 inches. | SWE = 0.40-0.65 inch. in. 90% probability of 5 to 11 inches. 10% probability up to 5 inches. | SWE = 0.30 to 0.60 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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