Avalanche Advisory: Wednesday - Dec 18, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 19, 2019 @ 6:47 am
Avalanche Advisory published on December 18, 2019 @ 6:47 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

South to Southwest winds increased overnight and are expected to continue today with gusts into the 50mph range over ridge tops. MODERATE avalanche danger exists at and above treeline due to the possibility of fresh sensitive wind slabs.  

 

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
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South to Southwest winds increased overnight and are expected to gust into the mid 50s today over ridge tops and into the 40s at mid-elevations. Fresh wind slab formation will be possible on exposed W to N to E to SE facing terrain features such as the leeward side of ridges and sidewalls of gullies. The fact that the snow in most exposed areas has already been wind effected by last weekends shifting winds will make these new wind slabs sneakier and not as widespread.  Be on the lookout for clues such as blowing snow, smooth rounded dense deposits and shooting cracks to help you identify areas of sensitive wind slab.  While likely to be small, a resulting slide could be consequential especially in steep rocky terrain or if a terrain trap is involved.  While most likely to find these at mid and upper elevations, winds at lower elevations today could result in isolated wind slabs bellow tree line as well.   

 
advisory discussion

The last snowfall in our area occurred last Saturday with a right-side up storm that dropped 3-6” of new snow.  This last storm came in quite warm initially resulting in a buried melt-freeze crust that can be found in many areas up to and above 9500’.  Recent snowpits have found some areas of weaker snow underneath this crust, with some Extended Column tests exhibiting propagating results.  This weak layer structure is worth keeping an eye on as it could become concerning with the potential of more snow this Sunday and next week.   

 
recent observations
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-12/17 - Bishop Area - Basin Mtn: Varibale alpine conditions, unreactive older windboard / wind slab.

-12/17 - Mammoth - Sherwins: Buried melt-freeze layer, no visible wind transport today.

Weather and CURRENT CONDITIONS
weather summary

A weak low pressure system will bring periods of light flurries for the mountains today, high temperatures in the mid 20s around 10,000’, and moderate S to SW winds gusting into the mid 50mph range over ridge tops. Little to no snow accumulation is expected except for the northern portion of the forecast zone where less than a half inch is possible. 

 

High pressure returns tonight thru Saturday resulting in warmer temperatures and clear skies until the next chance of snow on Sunday as another low pressure system moves in dropping temperatures.

 
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy. Isolated snow showers. Snow levels below 7000 feet. Chance of precipitation is 20%. Clear. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 25 to 31. deg. F. 13 to 18. deg. F. 33 to 39. deg. F.
Mid Slope Winds: Southwest 15 to 25 mph with gusts to 40 mph. Southwest around 15 mph. Gusts up to 30 mph in the evening. West around 15 mph with gusts to 30 mph.
Expected snowfall: less than 1 inch. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy. Scattered snow showers. Snow levels below 7000 feet. Chance of precipitation is 30%. Partly cloudy then becoming clear. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 19 to 25. deg. F. 10 to 15. deg. F. 27 to 33. deg. F.
Ridge Top Winds: South 25 to 40 mph with gusts to 55 mph becoming southwest 15 to 30 mph with gusts to 45 mph in the afternoon. Southwest 15 to 20 mph. Gusts up to 30 mph in the evening. West 15 to 25 mph.
Expected snowfall: up to 1 inch. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. 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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