Avalanche Advisory: Tuesday - Jan 26, 2021

THIS AVALANCHE ADVISORY EXPIRED ON January 27, 2021 @ 6:58 am
Avalanche Advisory published on January 26, 2021 @ 6:58 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Sensitive to stubborn wind slabs will be the primary avalanche concern for today due to fresh light snowfall over the weekend and varying levels of SW winds. MODERATE avalanche danger exists above treeline. While isolated pockets of wind slab may exist near treeline, overall avalanche danger is LOW near treeline and below where the greatest hazards continue to be the shallow snowpack and abundant obstacles.  Avalanche danger will rise dramatically overnight with major snowfall expected.  

2. Moderate

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

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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
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    Historic
    Very Large
    Large
    Small

2-9” of new low-density snow fell between Saturday and early morning Monday, wrapping up with SW winds.  Evidence of small natural avalanches were reported on Mammoth Mtn early Monday morning.  Mostly light SW winds today could still transport some snow over ridgetops and continue to build sensitive wind slabs at upper elevations. Older deeper wind deposits could be more stubborn to trigger.  Be wary of denser snow deposits particularly on NW-NE-SE facing slopes just below ridgelines and along the sidewalls of gullies.  Watch for shooting cracks and do your own localized assessments such as quick hand-pits to help determine how sensitive wind deposits may be.  While likely to be relatively small, triggering a wind slab could lead to a nasty ride thru obstacle-ridden terrain.     

advisory discussion

All eyes are on the up-coming storm system beginning late tonight lasting thru Friday morning which should completely change our drought-stricken snowpack. Avalanche danger will rise to levels unseen yet this season.  Plan on staying off and out from under steep slopes until this snow is done falling and has time to settle.  When the skies clear we should see a whole new playground awaiting us.  

recent observations
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-1/25 – Mammoth – Sherwins: 4-8” new snow, small sensitive wind slabs at ridgetop, concerning facet layer below old surface crust.

-1/25 – VA Lakes – SE Dunderberg: Dust on crust with isolated pockets of wind deposit up to 8” deep.

-1/25 – Mammoth Lakes Basin – Lake Mary Ridge: 4-8” new snow, facets below old surface crust.

-1/24 – Mammoth – Sherwins: New snow, winds, and small fresh sensitive wind slabs.

-1/24 – Mammoth – Red Cone: 2-4” New light snow, wind effects at upper elevations.

Weather and CURRENT CONDITIONS
weather summary

Today’s calm before the storm will offer mostly sunny skies and light SW winds with speeds and 10,000’ temperatures both in the mid-teens.  Flurries should begin late afternoon with heavy snowfall picking up after midnight and continuing thru Thursday night into Friday morning. Heavy snowfall with be accompanied by intense SW winds gusting up to 125mph over ridgetops.  This walloper of a storm system should deliver well over several feet of snow for our thirsty mountains, and snowline should stay below 5-6,000’.       

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: Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Mostly cloudy. Chance of snow in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 90%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%.
Temperatures: 15 to 21. deg. F. 13 to 19. deg. F. 20 to 26. deg. F.
Mid Slope Winds: Light winds becoming southwest around 15 mph in the afternoon. Gusts up to 30 mph. South 15 to 25 mph. Gusts up to 50 mph. South 20 to 35 mph with gusts to 70 mph.
Expected snowfall: 0 in. 80% probability of 4 to 10 inches. 20% probability of 1 to 4 inches. | SWE = 0.30-0.55 inch. in. 90% probability of 12 to 20 inches. 10% probability of 18-28 inches. | SWE = 1.10-1.60 inches. in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%. Mostly cloudy. Chance of snow in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 95%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 8 to 14. deg. F. 6 to 11. deg. F. 13 to 19. deg. F.
Ridge Top Winds: West 15 to 20 mph with gusts to 30 mph. Southwest 25 to 35 mph with gusts to 60 mph increasing to south 30 to 50 mph with gusts to 85 mph after midnight. South 40 to 60 mph with gusts to 100 mph.
Expected snowfall: 0 in. 80% probability of 5 to 10 inches. 20% probability of 1 to 5 inches. | SWE = 0.40-0.65 inch. in. 90% probability of 15 to 25 inches. 10% probability of greater than 25 inches. | SWE = 1.10-2.10 inches. 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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