Avalanche Advisory: Thursday - Jan 16, 2020

THIS AVALANCHE ADVISORY EXPIRED ON January 17, 2020 @ 7:00 am
Avalanche Advisory published on January 16, 2020 @ 7:00 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger will rise quickly throughout today as new snowfall begins this morning, with heavy rates of 2-3” an hour mid-afternoon thru this evening.  Extreme sustained S to SW winds will form dangerous wind slabs.  Avalanche danger will rise to HIGH by this evening at tree line and above and CONSIDERABLE below tree line due to wind slabs and storm slabs.  

 

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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With snowfall rates of 2-3” an hour expected this afternoon and evening and sustained S to SW winds gusting well over 100mph over ridge tops, dangerous wind slabs will become widespread on leeward slopes at all elevations.  Natural and human triggered avalanches will become likely in the afternoon and evening.  Watch for signs such as cornice formation, blowing snow, and shooting cracks to help avoid traveling on or under areas with denser wind deposited snow.  Underlying loose facet layers could lead to the potential of a smaller avalanche stepping down and becoming larger than expected. An avalanche today could certainly be large enough to bury a person.     

 
Avalanche Problem 2: Storm Slab
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6-12” of new snow is expected to fall at lower elevations this afternoon and evening, with 1-2ft expected at upper elevations, and rates as high as 2-3” an hour.  This new snow may not bond well to the old underlying surfaces which are a mix between firm and slick to loose and faceted.  In areas that receive greater amounts of new snow human triggered avalanches will become likely in steep terrain sheltered from the wind.  Watch for signs such as shooting cracks and avoid steep convexities and confined gully features where even a loose snow avalanche could be consequential.            

 
advisory discussion

 

In addition to the new snow concerns, underlying loose faceted snow layers which have been found scattered in various areas throughout the zone could become problematic where greater amounts of new snow is deposited by the wind.  A smaller wind slab avalanche could have the potential to step down and become larger than expected.  While many recent snowpits have identified looser faceted underlying snow layers, test results have not shown concerning failures or indications of propogation potential.  It will be interesting to see how a significant new snowload may affect these layers.       

Weather and CURRENT CONDITIONS
weather summary

*WINTER STORM WARNING IN EFFECT FROM NOON TODAY TO 1 AM FRIDAY*

 

A powerful cold front from the Gulf of Alaska will lead to snowfall beginning between 10-11am this morning and intensifying greatly mid-afternoon thru this evening with rates of 2-3” an hour.  6-12” of snow is expected for lower elevations and 1-2ft for upper elevations before tapering off after midnight.  Snow levels are expected to start ~4000’ and drop down to ~2000’. Very strong sustained S to SW winds are expected to gust between 100-130mph over ridge tops and decrease gradually thru the afternoon and night. Expect high temperatures in the upper teens above 10,000’.   

 

Dry and mild weather is on tap thru the holiday weekend, with potential for another storm on Tuesday.

 
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 then becoming cloudy. Snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 95%. Mostly cloudy. Snow in the evening, then chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 95%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures: 26 to 34. deg. F. 7 to 12. deg. F. 27 to 33. deg. F.
Mid Slope Winds: South 25 to 35 mph increasing to 30 to 45 mph in the afternoon. Gusts up to 95 mph. Southwest 25 to 35 mph with gusts to 70 mph decreasing to 15 to 20 mph with gusts to 35 mph after midnight. Southwest around 15 mph with gusts to 40 mph in the morning becoming light.
Expected snowfall: 70% probability of 3 to 9 inches. 30% probability of 2 to 6 inches. | SWE = 0.25-0.50 inch. in. 70% probability of 6 to 12 inches. 30% probability of 10 to 16 inches. | SWE = 0.30-0.55 inch. in. No Accumulation. | SWE = none. in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow in the evening, then chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 100%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures: 17 to 25. deg. F. 2 to 7. deg. F. 20 to 28. deg. F.
Ridge Top Winds: South 45 to 60 mph with gusts to 100 mph. Southwest 30 to 50 mph with gusts to 75 mph decreasing to 25 to 35 mph with gusts to 45 mph after midnight. West 20 to 30 mph with gusts to 45 mph decreasing to 15 to 20 mph with gusts to 30 mph in the afternoon.
Expected snowfall: 70% probability of 3 to 9 inches. 30% probability of 2 to 6 inches. | SWE = 0.30-0.55 inch. in. 70% probability of 6 to 12 inches. 30% probability of 10 to 16 inches. | SWE = 0.40-0.65 inch. 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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