Avalanche Advisory: Tuesday - Feb 12, 2019

THIS AVALANCHE ADVISORY EXPIRED ON February 13, 2019 @ 6:18 am
Avalanche Advisory published on February 12, 2019 @ 6:18 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists due to fresh wind slabs developing from last night and today’s increasing SW winds.  Human triggered avalanches will be possible. 

2. Moderate

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

2. Moderate

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

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    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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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Increasing SW winds will lead to new fresh wind slabs developing today in specific areas.  The strong and variable winds that accompanied this past weekend’s storm created widespread wind slabs, which appear to have bonded quite well by now.  Watch for smooth pillows of freshly deposited snow, shooting cracks, and blowing snow.  Avoid steeper committing terrain where fresh wind deposits may exist.  The leeward side of both ridgelines and across-slope terrain features are the most likely places to find these.  A resulting slide could still be large enough to bury a person today.  

advisory discussion

Yesterday’s observations show that the widespread storm slabs and wind slabs that formed during this past weekend’s big storm have settled and bonded well for the most part.  Continue to use safe travel protocols, recognize steep convexities as likely trigger points, and do your own localized assessments.    

recent observations

-2/12 - Mammoth - Laural Mtn - Bloody Mtn - Sherwins - Mammoth Crest: Winds visibly transporting snow over ridges at mid and upper elevations at dawn.

-2/11 - Mammoth - Punta Bardini: Blowing snow, evidence of in-storm avalacnhes, stabilizing conditions.

-2/11 - Mammoth - Sherwins: Very small skier trigger slide, overall stabilizing conditions.

-2/11 - Bishop - Bishop Bowl: Near surface faceting under crusts, shallow hollow snowpack still at low elevations.

-2/11 - Swall Meadows - Wheeler Crest: Wind effects/crusts.

-2/11 - Lee Vining - Dana Plateau: Wind transport, small shooting cracks, rollerballs on sunny slopes.

*Mammoth Mtn: Quite a lot of evidence of explosively or naturally triggered avalanches during the storm (~2/10), including one 6ft crown.  No results from control work on morning of 2/11 (bare in mind these slopes were controlled during the storm, and in-bounds slopes may not be representative of backcountry conditions).  

Weather and CURRENT CONDITIONS
weather summary

Winds are picking up again today ahead of another strong winter storm that will bring heavy dense snow from Wednesday morning thru Thursday.  Expect sunny skies this morning to become partly cloudy this afternoon, with a few inches+ of snow expected tonight.  Moderate SW winds will be on the increase throughout the day gusting into the 80s over ridge-tops by the afternoon, with high temperatures in the low to mid 20s around 10,000’.  

This upcoming storm will be quite different than the last, with greater amounts of moisture and a quickly rising snow-line, up to and possibly above 8000’.  Friday thru the weekend remains unsettled with more snow possible, and back to cold temperatures.  

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny then becoming mostly cloudy. Mostly cloudy. Chance of snow through the night. Snow levels below 7000 feet. Chance of precipitation is 50%. Snow. Rain in the afternoon at lower elevations. Snow levels below 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 95%.
Temperatures: 25 to 33. deg. F. 19 to 24. deg. F. 33 to 41. deg. F.
Mid Slope Winds: South 15 to 25 mph with gusts to 60 mph. South 15 to 30 mph shifting to the southwest 25 to 35 mph after midnight. Gusts up to 75 mph. Southwest 25 to 40 mph with gusts to 85 mph.
Expected snowfall: none in. 60% probability of 1 to 3 inches. 40% probability of 3 to 5 inches. | SWE = up to 0.25 inch. in. 90% probability of 9 to 15 inches. 10% probability of 15 to 20 inches. | SWE = 0.80-1.30 inches. in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny then becoming mostly cloudy. Mostly cloudy. Slight chance of snow in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 75%. Snow. Chance of precipitation is 100%.
Temperatures: 18 to 23. deg. F. 15 to 20. deg. F. 26 to 32. deg. F.
Ridge Top Winds: Southwest 25 to 35 mph with gusts to 60 mph increasing to 30 to 50 mph with gusts to 80 mph in the afternoon. Southwest 40 to 60 mph with gusts to 85 mph. Southwest 45 to 65 mph with gusts to 100 mph.
Expected snowfall: none in. 60% probability of 1 to 3 inches. 40% probability of 3 to 6 inches. | SWE = 0.15-0.25 inch. in. 90% probability of 12 to 20 inches. 10% probability of 18 to 26 inches. | SWE = up to 1.70 inches. 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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