Avalanche Advisory: Thursday - Jan 9, 2020

THIS AVALANCHE ADVISORY EXPIRED ON January 10, 2020 @ 6:33 am
Avalanche Advisory published on January 9, 2020 @ 6:33 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

For areas that receive more than 2” of new snow this morning MODERATE avalanche danger will develop at tree line and above due to moderate west winds forming new fresh sensitive wind slabs.  LOW avalanche danger exists otherwise.

 

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
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

1-3” of new snowfall is likely this morning before noon accompanied by moderate west winds gusting into the 40 mph range at mid and upper elevations.  For areas that DO receive this new snowfall, new wind slabs will readily form on the leeward side of ridges, sidewalls of gullies and in other mid-slope catchment zones.  Keep in mind that wind can deposit snow >5x faster than it can fall out of the sky, so new wind slabs could easily be over a foot thick.  Be on the lookout for fresh pillows of snow, shooting cracks, blowing snow and cornice formation to help you decide where to travel safely.  Human triggering of avalanches will be possible.  Even a small avalanche could lead to a nasty ride with the very firm underlying snow conditions.   

 
advisory discussion

Snow surfaces have been extremely variable prior to today’s potential snowfall.  Firm slide-for-life conditions exist for most exposed areas, and a couple inches of new soft snow ontop will not change that danger.  These firm smooth surfaces will make it easy for a fresh wind slab to fail and slide on as well. Soft faceted surface snow exists in many protected areas and a new wind slab on top of this loose snow could fail easily as well.       

 
recent observations
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-1/8 - Mammoth - Sherwins: Variable surfaces.

-1/5-7 - Tuolumne: Conditions.

-1/7 - Mammoth - Sherwins: Variable snow surfaces, near surface faceting, wind effects.

-1/7 - Mammoth - Behind Mammoth: Snowpack, variability.

-1/7 - June - Negatives, Hemlocks: Wind effects, faceting sheltered snow.

-1/7 - June - Nagatives: Snowpack and surface conditions and weather.

-1/7 - Mammoth - Punta Bardini: Sugary snow and crusts.

Weather and CURRENT CONDITIONS
weather summary

Light snow showers are likely this morning, with 1-3” of new snow possible before clearing this afternoon.  Expect temperatures to reach the low to mid 20s around 10,000’, and moderate west winds at mid to upper elevations to gust into the 40mph range.

 

A migratory ridge will keep things clear and dry until the weekend, when slight chances of minimal snow showers return thru the beginning of next week.  Beyond that models are in disagreement, but more favorable scenarios show the possibility of more significant storms for late next week into the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 65%. Clear. Snow levels below 7000 feet. Chance of precipitation is 5%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 23 to 31. deg. F. 11 to 16. deg. F. 34 to 42. deg. F.
Mid Slope Winds: West 15 to 20 mph with gusts to 40 mph. Northwest 15 to 20 mph with gusts to 45 mph. West around 15 mph. Gusts up to 40 mph decreasing to 30 mph in the afternoon.
Expected snowfall: 90% probability of 1 to 3 inches. 10% probability of 3 to 5 inches. | SWE = up to 0.15 inch. in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Snow in the morning, then chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 75%. Clear. Snow levels below 7000 feet. Chance of precipitation is 5%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 15 to 23. deg. F. 6 to 11. deg. F. 26 to 34. deg. F.
Ridge Top Winds: West 15 to 30 mph. Gusts up to 45 mph decreasing to 35 mph in the afternoon. North 20 to 35 mph shifting to the northwest 30 to 40 mph after midnight. Gusts up to 60 mph. Northwest 25 to 35 mph with gusts to 55 mph decreasing to 15 to 25 mph with gusts to 40 mph in the afternoon.
Expected snowfall: 90% probability of 1 to 3 inches. 10% probability of 3 to 5 inches. | SWE = up to 0.15 inch. 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.

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