Avalanche Advisory: Thursday - Dec 5, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 7, 2019 @ 5:51 am
Avalanche Advisory published on December 5, 2019 @ 5:51 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Fresh wind slabs at upper elevations and soft storm slabs at mid to lower elevations are the main avalanche concern for Thursday thru Friday.  4-8” of new snow fell during the day on Wednesday with moderate SW winds near ridge tops. Winds are expected to increase Friday making wind slabs more widespread at lower elevations.   

 

*Danger ratings can not be assigned accurately for multi-day advisories as conditions can change too much over that time period.  Daily advisories with danger ratings will begin by Dec 20th.    

 
 

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Above Treeline

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Near Treeline

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Below Treeline
advisory discussion

Prior to Wednesday’s storm field observations and settlement rates indicate that the underlying snowpack has settled well.  4-8” of new snow fell during the day Wednesday with calm winds below tree line and moderate winds out of the SW near ridge tops.  Fresh wind slabs formed and will continue to form in exposed upper elevation areas as ridge top winds continue thru Thursday and increase Friday effecting lower elevation areas.  6-10” storm slabs were skier triggered Wednesday afternoon in steep convexities, and 1-1.5ft wind slabs in exposed upper elevations just below ridge lines.  

 

Avoid denser snow deposits below ridge lines especially on NW thru NE to SE facing slopes. Use clues such as cornice formation and blowing snow that indicate where fresh wind slabs may be.  As winds increase on Friday and shift out of the south these wind slabs will likely develop in more widespread areas further downslope.  

 

Be cautious of steep convexities where soft storm slabs and sloughing could remain sensitive to human triggering in un-wind affected areas, especially where terrain traps are involved.  These will become less and less sensitive as time goes by.

 
recent observations
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-12/04 - Mammoth - Sherwins: Sensitive wind slabs and storm slabs. 

-12/04 - Mammoth Area: Ski cuts resulted in 1-1.5ft wind slabs running 300-400ft.  

-12/03 - Mammoth Lakes Basin - Red Cone: Snow conditions.

-12/03 - Mammoth Mountain - Upper elevation snow profile and stability. 

Weather and CURRENT CONDITIONS
weather summary

A Break in storms is expected for Thursday and Friday before another significant storm is expected to move into our area Friday night thru Sunday with over 2ft of new snow expected.

 

For Thursday expect partly sunny skies, high temperatures near freezing around 10,000ft and ridge top winds out of the SW gusting up to 30mph.  Thursday night thru Friday winds will increase gusting up to 60mph out of the south over ridge tops and up to 25mph at mid elevations.  

 
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 0%. Mostly cloudy then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 32 to 37. deg. F. 21 to 26. deg. F. 33 to 38. deg. F.
Mid Slope Winds: Light winds. Light winds becoming south around 15 mph with gusts to 25 mph after midnight. South 10 to 15 mph with gusts to 25 mph.
Expected snowfall: No accumulation. | SWE = none. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 0%. Mostly cloudy then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 29 to 34. deg. F. 19 to 24. deg. F. 28 to 34. deg. F.
Ridge Top Winds: Southwest 15 to 20 mph. Gusts up to 30 mph in the afternoon. Southwest 15 to 30 mph. Gusts up to 50 mph after midnight. South 20 to 35 mph with gusts to 60 mph.
Expected snowfall: No accumulation. | SWE = none. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. 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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