Avalanche Advisory: Sunday - Dec 15, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 16, 2019 @ 6:52 am
Avalanche Advisory published on December 15, 2019 @ 6:52 am
Issued by Steve Mace - ESAC

MODERATE avalanche danger exists at mid and upper elevations and LOW avalanche danger exists at lower elevations. Wind slabs remain the primary concern particularly on specific terrain features at mid and upper elevations. Evaluate the snow carefully before committing to suspect terrain.

 

2. Moderate

?

Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

?

Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

6” of new snow fell in the Mammoth area over the past two days accompanied by powerful southwest winds. Expect continued wind slab development to occur on leeward slopes throughout the day today as moderate winds continue to impact the area.  Fresh, sensitive wind slabs will be most prevalent on northerly and easterly aspects at mid and upper elevations. However, with winds expected to shift to the NW today, we may start to see loading on more southerly facing terrain.  Be on the lookout for specific terrain features that encourage wind slab development, such as the leeward sides of ridgelines, convex rolls, and the sidewalls of gullies. Use surface clues such as drifted snow, recent cornice growth, stiff hollow sounding snow, and uneven snow surface to identify and avoid wind-loaded areas.  

advisory discussion

We have had an incredible start to the 2019/20 season here in the Sierra.  For the most part, observations have identified a well bonded and right side up snowpack with current avalanche problems concentrated in the upper portions of the snowpack.  Keep a keen eye out for signs of wind deposit today, and don’t be surprised to find isolated pockets of wind slab at lower elevations. It is also important to keep in mind that the snowpack is still relatively thin and preseason obstacles are a real concern. Furthermore, fresh snow, strong winds, and recent rain showers have created a variety of surface conditions ranging from soft powder to slick supportable ice.  Evaluate local snow conditions and pick your travel routes carefully if you head into the backcountry today.

Weather and CURRENT CONDITIONS
weather summary

Expect partly cloudy skies this morning, becoming sunny by this afternoon.  Temperatures will remain below freezing throughout the day with highs in the Mid 20’s at lower elevations. Moderate winds are expected to shift to the northwest with ridgetop gusts around 45 mph. Temperatures may drop into the low teens tonight with continued moderate winds and clear skies. 

High pressure is expected to build for the early part of next week, bringing lower wind speeds and warmer temperatures to the range.  A week storm is possible mid-week that may bring trace amounts of precipitation on Wednesday. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy then becoming sunny. Slight chance of snow in the morning. Snow levels below 7000 feet. Chance of precipitation is 20%. Clear. Sunny.
Temperatures: 21 to 27. deg. F. 6 to 12. deg. F. 24 to 30. deg. F.
Mid Slope Winds: Northwest 10 to 20 mph with gusts to 35 mph. Northwest around 15 mph in the evening becoming light. Gusts up to 30 mph. Light winds.
Expected snowfall: Little or no accumulation. | SWE = trace amounts. in. 0 in. 0 in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy then becoming sunny. Slight chance of snow in the morning. Snow levels below 7000 feet. Chance of precipitation is 20%. Clear. Sunny.
Temperatures: 14 to 20. deg. F. 5 to 11. deg. F. 19 to 25. deg. F.
Ridge Top Winds: West to northwest 15 to 30 mph with gusts to 45 mph. Northwest 15 to 25 mph with gusts to 40 mph. Northeast around 15 mph with gusts to 30 mph.
Expected snowfall: Little or no accumulation. | SWE = trace amounts. in. 0 in. 0 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.

ESAC receives significant financial support from ...