Avalanche Advisory: Friday - Feb 15, 2019

THIS AVALANCHE ADVISORY EXPIRED ON February 16, 2019 @ 6:42 am
Avalanche Advisory published on February 15, 2019 @ 6:42 am
Issued by Steve Mace - ESAC

High avalanche danger exists at all elevations today. Strong southwest winds and heavy snowfall will continue to make for hazardous conditions.   Travel in or underneath avalanche terrain is not recommended.

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.

4. High

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Below Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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With another 17” of new snow expected today coupled with strong southwest winds expect large sensitive wind slab development in areas where terrain features encourage drifting such as the leeward sides of ridgelines and the sidewalls of gullies. Use surface clues such as blowing snow, drifting, new cornice growth, and uneven snow surface to identify and avoid wind-loaded areas. 

Gale force winds were noted throughout the day yesterday even at lower elevations.  Gusts were recorded as high as 175mph on the summit of Mammoth Mountain.  Expect snow to have redistributed in unusual and unpredictable ways. It will be likely to find areas of wind deposit in places you may not normally expect such as further down slopes and in more protected areas even at lower elevations. Keep in mind that the fresh snow cover will make surface clues more challenging to see, treat all suspect slopes with caution.

Avalanche Problem 2: Storm Slab
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With continued heavy snowfall we are likely to see storm slab development today particularly in areas protected from the wind. The recent rain event could exasperate this problem.  Dense wet snow is overlying dry unconsolidated snow creating a weak structure. This problem is specific to lower elevations, but recent observations have found this new rain crust to be reactive in stability tests. Watch for signs of instability such as shooting cracks, wumphing or recent avalanche activity. Travel on or underneath slopes greater than 30° is not recommended.

advisory discussion

As the holiday weekend approaches, it will be important to remain cautious.  Ample new snow and strong, unpredictable winds have led to instabilities across the compass at all elevations.  Dig in and do your own localized assessments to evaluate the now buried rain crust, look for signs of wind loading and approach all suspect terrain with extreme caution.  Things are likely to be sensitive today, its best to avoid traveling in, or underneath avalanche terrain.

recent observations
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2/14-Mammoth Area, Gale force winds near Mammoth Rock

2/14- Mammoth Area, Forest trail knoll 

2/14- Mammoth Area, Snow Conditions in the Sherwins

2/13- Mammoth Area, Rain on Snow in the Sherwins

2/13- Mcgee Mtn, Rain on snow

2/12- Bishop Creek, Snow conditions

Weather and CURRENT CONDITIONS
weather summary

*Winter Storm Warning is in effect until 1200 on Sunday*

 

Winter weather continues today with heavy snow and strong southwest winds.  Up to 17” of new snow is predicted, and ridge top winds are expected to reach over 100 mph.  Temperatures will be cold today with highs in the mid-teens.  Expect slightly slower wind speeds and smaller snow totals as temperatures drop even further tonight into the single digits. 3-7” of snow expected this evening.

Temperatures remain cold tomorrow with moderate winds expected out of the southwest and 3-7” of snow expected during daylight hours.  Winter weather and cold temperatures are expected to continue through the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 90%. Mostly cloudy. Snow in the evening, then chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 75%. Mostly cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 85%.
Temperatures: 20 to 28. deg. F. 9 to 14. deg. F. 17 to 25. deg. F.
Mid Slope Winds: Southwest 25 to 40 mph with gusts to 75 mph. Southwest 20 to 35 mph with gusts to 75 mph. Southwest 20 to 35 mph with gusts to 70 mph decreasing to 15 to 25 mph with gusts to 50 mph in the afternoon.
Expected snowfall: 80% probability of 8 to 16 inches. 20% probability of 15 to 20 inches. | SWE = up to 0.70 inch. in. 80% probability of 3 to 7 inches. 20% probability of 6 to 10 inches. | SWE = up to 0.30 inch. in. 80% probability of 3 to 6 inches. 20% probability of 5 to 10 inches. | SWE = 0.15-0.25 inch. in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow in the evening, then snow likely after midnight. Snow levels below 7000 feet. Chance of precipitation is 85%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 90%.
Temperatures: 13 to 18. deg. F. 4 to 9. deg. F. 9 to 15. deg. F.
Ridge Top Winds: Southwest 50 to 70 mph with gusts to 105 mph decreasing to 35 to 55 mph with gusts to 85 mph in the afternoon. Southwest 35 to 55 mph with gusts to 80 mph. Southwest 40 to 55 mph decreasing to 30 to 45 mph in the afternoon. Gusts up to 80 mph.
Expected snowfall: 80% probability of 9 to 17 inches. 20% probability of 15 to 20 inches. | SWE = 0.55-0.80 inch. in. 80% probability of 3 to 7 inches. 20% probability of 6 to 10 inches. | SWE = 0.20-0.45 inch. in. 80% probability of 3 to 7 inches. 20% probability of 6 to 12 inches. | SWE = up to 0.30 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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