Avalanche Advisory: Tuesday - Dec 24, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 25, 2019 @ 6:44 am
Avalanche Advisory published on December 24, 2019 @ 6:44 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists at Upper and Middle elevations on North–East Aspects. LOW avalanche danger exists at Lower elevations. Wind Slab & Loose Dry Snow avalanches will be of primary concerns with upwards of 14” of recent snow. Observations in the Upper zone have been limited since the latest storm; for areas that potentially received greater amounts of new snow or where more wind transport occurred, CONSIDERABLE avalanche danger may exist.

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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Fresh wind deposits adjacent to ridgelines on North - Easterly aspects likely have begun to settle and stiffen overnight. Wind slabs may become more reactive than was observed yesterday and will be specific to exposed leeward alpine terrain.  Although likely small in nature, human triggered wind slabs are possible in the usual suspect locations (leeward terrain, gullies, confined entrances to chutes and slopes conducive to capturing snow). Today’s winds are again forecasted to be light-moderate and we may not see much snow transport, but be aware and ready to adjust to changing conditions. Look out for the red flags of active wind loading, recent avalanches and shooting cracks while you travel today.

Avalanche Problem 2: Loose Dry
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Loose-dry snow sloughing will be a potential hazard in steep and confined terrain. Light winds and cold temps have helped keep dry powder conditions all the way up to ridgeline in many areas. Slides small in nature can be hazardous in terrain exposed to fall hazards. Many smooth old snow surfaces existed before this fresh snowfall including temperature crusts and slick wind board. Avoid terrain traps in your area and be critical of slope angles over 35degrees.

advisory discussion

It’s been a real treat to get some fresh snow for the holidays! Yesterday’s backcountry observations from tree line down confirmed amazing skiing conditions with little to no wind effect. Limited observations were reported in the Upper elevations as the high country was pretty socked in. Mammoth patrol did get to the top of the mountain and reported some minor natural activity, D1 potential for loose snow sloughing, and limited shallow storm slab results during explosive work. Snow totals across the forecast zone varied from 6-16” with ~1.4” of SWE (Snow Water Equivalent) in the Mammoth area. Although there was variety of smooth old snow surfaces such as slick crusts and hard wind eroded surfaces, this most recent storm had bonded well and was right side up yesterday. The only thing moving Monday was some loose snow sloughing which was minimal in nature.

Winds continued to be very light to non-existent overnight in the mid-low elevations, with some steady moderate winds recording at the top of the ski area. As always re-evaluate today and do your own assessments in safe locations to check if some of the deeper pockets of snow in leeward terrain have gained more tension or reactivity to skier trigger.

Some lingering old rain crusts and upside down hardness profiles did not record any signs of instability yesterday, but we will continue to track the metamorphism of these old layers that last week were showing a propensity for propagation in snow stability tests.

Early Season Obstacles Exist!  Take note that although there is a decent snowpack in the Mammoth area and high elevations of the forecast zone, a majority of the area still has limited coverage.

Weather and CURRENT CONDITIONS
weather summary

Another cloudy day is slated for the area with light winds and chance of snow throughout today and tonight. 1” of snow is on tap for today with trace amounts tonight. The forecast for winds is almost identical as yesterday with light to moderate southerly winds with some stronger gusts at ridge top ~30mph. However, field observations yesterday  in the Mammoth and June area observed little to no wind at all, and certainly no gusts of note. We will see how today plays out, but it's been a nice break from our normally windy regime here. Temperatures should remain below freezing for the day and it will be another cold night for Santa and his reindeer with lows getting into the single digits.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Snow levels Chance of precipitation is Snow levels Chance of precipitation is Snow levels Chance of precipitation is
Temperatures: deg. F. deg. F. deg. F.
Mid Slope Winds:
Expected snowfall: | SWE = in. | SWE = in. | SWE = in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Snow levels Chance of precipitation is Snow levels Chance of precipitation is Snow levels Chance of precipitation is
Temperatures: deg. F. deg. F. deg. F.
Ridge Top Winds:
Expected snowfall: | SWE = in. | SWE = in. | SWE = 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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