Avalanche Advisory: Tuesday - Dec 4, 2018

Avalanche Advisory published on December 4, 2018 @ 6:45 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

With light snowfall and light southerly winds with moderate gusts expected from now until Thursday, the greatest avalanche concern for Tuesday and Wednesday will be fresh wind slabs forming on exposed mid to upper elevation slopes facing E-N-W. Expect to find these on the leeward side of ridges, the sidewalls of gullies and around other features that promote drifting.  Human triggered avalanches will become increasingly possible during this time.      

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Above Treeline

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Below Treeline
Avalanche Problem 1: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Up to 6” of new snow is expected to fall between now and Thursday accompanied by light southerly winds with gusts into the 30-40mph range at mid to upper elevations.  While a few inches of light snow isn’t much to worry about on it’s own, add wind into the equation and much deeper and more dangerous wind deposits are possible that could end in an avalanche large enough to bury a person.  The fact that these will not likely be widespread makes it more tricky, and even more important to keep a keen eye out.  Be on the lookout for denser snow deposits, and watch for clues such as blowing snow and cornice formation to indicate areas to avoid where fresh wind slabs may exist. 

advisory discussion

Last week storms brought in 2-3.5’ of snow accompanied by strong SW winds, providing a supportable, all-be-it shallow, base of snow and start to the backcountry touring season with few if any underlying weak layer concerns.  Sunday was a beautiful calm, cold, yet sunny day which allowed wind slabs from Saturday time to bond.  Reports came back of some people seeing evidence of D2 wind slab avalanches in several areas which occurred mid storm.  Monday cloud cover increased as well as upper elevation winds, which transported snow in some areas and likely led to isolated small patches of fresh wind slab.  With light snowfall expected Tuesday into Thursday accompanied by light winds with moderate gusts from the south, fresh isolated wind slabs will be our greatest avalanche concern in exposed mid to upper elevation areas.     

Early season obstacles exist!  Plenty of rocks, logs, and tree stumps are lurking just under the surface, and we've heard of atleast one snowboard that has just bitten the dust.  

A skier triggered avalanche occurred in the tahoe area on Sunday 12/2.  While this is outside our forecast area, it is still the Sierra and we can learn from it.  Remember to keep vigilant out there, not let your guard down, and practice safe one-at-a-time travel protocols.   Click here for detailed report from the party and good photos.

weather summary

Chances of light snow will continue from now thru Thursday afternoon with up to 6” falling by Thursday evening (lighter amounts south towards the mountains above Bishop).  Snowline should stay below 6,500’.  For Tuesday and Wednesday expect high temperatures in the mid 20s around 10,000’ and light southerly winds with gusts reaching 40mph.    

High pressure will return for the weekend, with another chance of snow early next week.  

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: Cloudy. Scattered snow showers. Cloudy. Snow likely. Mostly cloudy. Chance of snow in the morning, then snow showers likely in the afternoon.
Temperatures: 27 to 32 deg. F. 18 to 23 deg. F. 27 to 32 deg. F.
Mid Slope Winds: South to southeast Southeast South
Expected snowfall: up to 1 inch. in. 60% probability of 1 to 3 inches. 40% probability up to 1 inch. in. 60% probability up to 2 inches. 40% probability no accumulation. in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Cloudy. Scattered snow showers. Cloudy. Snow. Cloudy. Snow showers likely.
Temperatures: 22 to 27 deg. F. 17 to 22 deg. F. 22 to 27 deg. F.
Ridge Top Winds: South South South
Expected snowfall: up to 2 inches. in. 70% probability of 2 to 4 inches. 30% probability up to 2 inches. in. 60% probability of 2 to 4 inches. 40% probability up to 2 inches. in.
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 Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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