Avalanche Advisory: Saturday - Dec 21, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 22, 2019 @ 6:58 am
Avalanche Advisory published on December 21, 2019 @ 6:58 am
Issued by Steve Mace - ESAC

The avalanche danger will rise to MODERATE today at mid and upper elevations while remaining LOW at lower elevations. Pockets of fresh sensitive wind slab will be the greatest concern on northerly and easterly aspects near and above treeline. Heightened avalanche conditions exist, evaluate snow and terrain carefully.

2. Moderate

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

2. Moderate

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

1. Low

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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
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    Certain
    Very Likely
    Likely
    Possible
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    Historic
    Very Large
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While minimal amounts of snow are available for transport, the prevailing southwest winds are expected to rise significantly today. Mid slope winds will be strong with ridgetop gusts as high as 90 mph by late this afternoon. It will be important to keep in mind that gale-force winds can distribute snow in unpredictable ways.  Fresh, sensitive wind slabs are most likely to form on northerly and easterly aspects at mid and upper elevations. However, their distribution will be isolated to areas where loose surface snow is available for transport. Be particularly suspect of mid-slope depressions, cross-loaded gully features, and leeward slopes at mid-elevations.  Use surface clues such as blowing snow, drifting, and uneven snow surfaces to identify wind loaded areas and do your own localized assessments before committing to a suspect slope. While resulting avalanches are likely to be small, there may be enough snow to take a skier off their feet and carry them through unpleasant terrain.

 

advisory discussion

Beyond the concern of fresh wind slabs today it will still be possible to find isolated areas where lingering wind slabs are sitting on weak faceted snow below. This structure is likely isolated to specific terrain features on more northerly aspects at mid and upper elevations where a relatively thin snowpack exists. While resulting avalanches will be hard to trigger they would not be without consequence. Don’t be afraid to dig in and evaluate the structure before committing to suspect terrain. 

In addition, variable surface conditions remain a hazard throughout the forecast area. Generally thin coverage, early season obstacles, and a variety of hard slick conditions have been reported throughout the range. Travel in many areas is difficult, and a fall in the wrong place could be unpleasant. Be prepared for a variety of Surface conditions ranging from loose recycled powder, to breakable and supportable crusts if you head into the backcountry today. 

Weather and CURRENT CONDITIONS
weather summary

 Sunny skies and pleasent temperatures are on tap for today as an incoming storm system brings gusty winds to the east side. Southwest winds are expected to increase throughout the day with ridgetop gusts pushing 90 mph this afternoon. Expect the temperature to be close to 40°F at lower elevations and near freezing at 10,000’.

 

Snow showers are expected to impact the forecast area starting early on Sunday morning.  Snow totals are not expected to be huge. 4-8” may accumulate at higher elevations along the crest with more moderate amounts at lower elevations as strong winds continue to impact the area. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Partly cloudy. Sunny then becoming mostly cloudy. Chance of snow in the morning, then snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 80%.
Temperatures: 37 to 43. deg. F. 20 to 25. deg. F. 29 to 35. deg. F.
Mid Slope Winds: South 20 to 30 mph increasing to 30 to 45 mph in the afternoon. Gusts up to 65 mph. South 25 to 35 mph with gusts to 60 mph. South 20 to 35 mph. Gusts up to 60 mph decreasing to 60 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 80% probability of 2 to 5 inches. 20% probability of 5 to 7 inches. | SWE = 0.15-0.40 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Partly cloudy. Partly cloudy then becoming cloudy. Chance of snow in the morning, then snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 85%.
Temperatures: 30 to 36. deg. F. 16 to 21. deg. F. 22 to 28. deg. F.
Ridge Top Winds: Southwest 30 to 50 mph with gusts to 65 mph increasing to 40 to 60 mph with gusts to 85 mph in the afternoon. South 45 to 60 mph increasing to 50 to 70 mph after midnight. Gusts up to 95 mph. South 40 to 60 mph with gusts to 85 mph decreasing to 35 to 50 mph with gusts to 65 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 80% probability of 2 to 5 inches. 20% probability of 5 to 7 inches. | SWE = 0.20-0.45 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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