Avalanche Advisory: Saturday - Mar 2, 2019

THIS AVALANCHE ADVISORY EXPIRED ON March 3, 2019 @ 6:55 am
Avalanche Advisory published on March 2, 2019 @ 6:55 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

As 1-1.5ft of new snow accumulates throughout the day with moderate S to SW winds, avalanche danger will quickly rise to HIGH at mid to upper elevations and CONSIDERABLE at lower elevations due to wind slabs and storm slabs.  Natural and human triggered avalanches will be likely. 

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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Light S to SW winds this morning will increase throughout the day with gusts expected into the 60mph range even at lower elevations.  These winds will easily transport fresh snow into large dangerous sensitive wind slabs.  Older more stubborn wind slabs created by yesterday’s very strong SW winds will also remain a concern.  Watch for areas of denser snow particularly on the leeward side of ridgelines, sidewalls of gullies and across slope deposition areas.  Blowing snow, cornice formation, and other surface clues can help you identify potential areas of concern.  Avalanches today could easily bury a person.  Avoid traveling on or under wind-loaded slopes.    

Avalanche Problem 2: Storm Slab
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1-1.5ft of new snow expected by this afternoon will make human triggering of storm slab avalanches increasing likely thru the day in areas not affected by the wind.  Watch for steep convexities as likely trigger points, and do your own localized assessments before traveling in steeper sheltered terrain.  Areas of previously exposed old rain, melt-freeze, and firm wind-board will make for smooth surfaces for new snow to slide on.  Loose snow sloughs could be large enough to sweep a rider off their feet, and a burial could be possible especially where terrain traps are involved.   

Avalanche Problem 3: Cornice
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As winds increase today, large dangerous cornices are likely to form on the leeward side of ridgelines.  Mammoth ski patrol reported large cornice formation earlier this week from much lesser amounts of new snowfall.  Cornices can fail much further back from the edge of a ridge than expected.  Give the edges of ridgelines a wide berth.  A resulting fall from a cornice collapsing under your feet could be deadly especially if above unseen cliffs.  A large cornice fall could also trigger a large slope-wide avalanche.

advisory discussion

In various areas avalanches over the past couple of weeks have occured sliding on the rain crust and melt-freeze crust that formed over Valentine's day, leaving this crust exposed and even slicker.  Click this link for details on a slide that occured behind June Mtn.  Keep in mind that it will likley be even harder for new snow to bond to these crust, and avalanches are likely to occur again in these same areas.        

Weather and CURRENT CONDITIONS
weather summary

March begins with a modest Pacific storm. Snowfall began early this morning, and should continue with intensities greater than an inch an hour before tapering off this afternoon.  New snow totals of 1-1.5ft are expected before dark, with rain possible below around 7,500’. Winds will intensify throughout the day out of the S to SW gusting into the 60mph range.  Chances of light flurries continue tonight thru tomorrow with continued moderate SW winds.  

A more significant warm Atmospheric River event is looking possible for Tue and Wed, with another colder storm lining up for the weekend.

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. Snow. Snow levels 7000 feet. Chance of precipitation is 95%. Partly cloudy then becoming mostly cloudy. Chance of snow showers. Snow levels 7000 feet. Chance of precipitation is 45%. Mostly cloudy then becoming partly cloudy. Chance of snow showers through the day. Slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 30%.
Temperatures: 31 to 39. deg. F. 23 to 28. deg. F. 31 to 39. deg. F.
Mid Slope Winds: Southwest 15 to 30 mph. Gusts up to 45 mph increasing to 70 mph in the afternoon. Southwest 15 to 30 mph with gusts to 75 mph. Southwest 15 to 20 mph with gusts to 60 mph.
Expected snowfall: 80% probability of 5 to 11 inches. 20% probability of 12 to 15 inches. | SWE = 0.40-0.65 inch. in. up to 2 inches. | SWE = less than 0.10 inch. in. up to 2 inches. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Cloudy. Snow. Snow levels 7500 feet. Chance of precipitation is 95%. Mostly cloudy. Chance of snow showers. Snow levels 7000 feet. Chance of precipitation is 50%. Mostly cloudy. Chance of snow showers. Snow levels 7000 feet. Chance of precipitation is 40%.
Temperatures: 23 to 29. deg. F. 18 to 23. deg. F. 23 to 29. deg. F.
Ridge Top Winds: South 25 to 35 mph shifting to the southwest 30 to 45 mph in the afternoon. Gusts up to 65 mph. Southwest 30 to 45 mph with gusts to 70 mph. Southwest 30 to 45 mph decreasing to 25 to 35 mph in the afternoon. Gusts up to 65 mph.
Expected snowfall: 90% probability of 9 to 14 inches. 10% probability of 14 to 18 inches. | SWE = 0.55-1.00 inch. in. up to 2 inches. | SWE = less than 0.10 inch. in. up to 2 inches. | 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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