Avalanche Advisory: Tuesday - Mar 17, 2020

THIS AVALANCHE ADVISORY EXPIRED ON March 18, 2020 @ 7:00 am
Avalanche Advisory published on March 17, 2020 @ 7:00 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

1-2.5ft of new snow has fallen over the past 2.5 days with periods of strong SW winds.  Avalanche danger is CONSIDERABLE above treeline and MODERATE at treeline and a bit below due to the possibility of dangerous wind slabs.  Loose dry sloughing will be concerning in steep sheltered terrain. 

 

Avalanche danger is more concerning for areas around Mammoth and north which received more new snow than areas further south.   

 

3. Considerable

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

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.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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The relatively light winds yesterday picked up noticeably overnight for a period gusting between 40-60mph out of the SW over ridges at mid and upper elevations.  30mph SW gusts are expected today, which is strong enough to continue to transport snow over ridges.  Watch for denser wind deposited snow below ridgelines, the sidewalls of gullies, and across slopes around rock outcrops particularly at upper elevations.  Use clues such as blowing snow, cornice formation and shooting cracks to help you avoid areas of dangerous wind deposits. A windslab avalanche today could injure or bury a person.

Avalanche Problem 2: Loose Dry
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Field observations yesterday found very sensitive sloughing conditions in steep terrain that ran far.  With today’s cold temperatures, loose dry sloughing will continue to be a concern in sheltered steep terrain.  Without careful management it could easily sweep a rider off their feet and into obstacles and potentially lead to a burial if a terrain trap is involved.  

 
advisory discussion

Storm snow in sheltered areas from the past couple of days has been found to be mostly right-side-up and bonding well.  However, a weak underlying snowpack exists in many areas.  On sheltered northerly facing slopes at mid-elevations a melt-freeze crust has been found just below the new snow with a layer of loose faceted snow underneath that raises some concern.  While tests yesterday could not find areas where a significant enough slab existed above this weak layer to make a slope failure possible, it is something to keep in mind and assess locally. Spend a few minutes to take your shovel out and do your own tests especially as this new snow settles and could become more of a cohesive slab.  Let us know what you find thru our observations page.

 

Sunny skies are expected this morning before some clouds return in the afternoon.  Although temperatures will remain fairly cool, sunshine on new snow could result in some small loose-wet point releases, likely originating from rock outcrops.

 

And remember, a shallow snowpack with many obstacles existed prior to this new snow. Sharks in the form of rocks, stumps and logs are lurking just below this new snow surface!  

Weather and CURRENT CONDITIONS
weather summary

Expect sunny skies this morning with SW winds gusting to 30 mph decreasing thru the day.  Clouds and a chance of light flurries returns in the afternoon.  Temperatures will remain cool with highs only reaching the low 20s F around 10,000’.  

 

Looking ahead weather remains unsettled with chances of light snow everyday with little accumulation expected until Sunday evening and early next week when models show potential for more significant snowfall.

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 partly cloudy. Slight chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 25%. Partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 15%. Mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 35%.
Temperatures: 22 to 30. deg. F. 7 to 13. deg. F. 27 to 35. deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 30 mph. Light winds. Gusts up to 25 mph after midnight. Light winds.
Expected snowfall: up to 1 inch. | SWE = trace amounts. in. up to 1 inch. | SWE = trace amounts. in. up to 1 inch. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny then becoming partly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 30%. Partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy then becoming mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 40%.
Temperatures: 12 to 20. deg. F. 1 to 6. deg. F. 17 to 25. deg. F.
Ridge Top Winds: Southwest 15 to 25 mph. Gusts up to 35 mph decreasing to 25 mph in the afternoon. Southwest around 15 mph with gusts to 25 mph. Southwest around 15 mph.
Expected snowfall: up to 1 inch. | SWE = trace amounts. in. up to 1 inch. | SWE = trace amounts. 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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