Avalanche Advisory: Friday - Jan 25, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 26, 2019 @ 6:57 am
Avalanche Advisory published on January 25, 2019 @ 6:57 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

MODERATE avalanche danger remains today due to the uncertainty surrounding an unlikely but not impossible persistent slab avalanche. Other concerns include small loose-wet avalanches on sunny slopes, and new small wind slabs this afternoon at upper elevations.  Make terrain choices based on your own local assessments. 

1. Low

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

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: Persistent Slab
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    Very Likely
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Reports were confirmed last night that 3 natural D2 avalanches occurred 3 days ago on Tuesday on Mt. Tom.  That combined with continued reports of poor snowpack structure and some reactive test results will keep the avalanche danger at MODERATE today.  While unlikely, a large deadly persistent slab avalanche is not impossible, particularly in areas with shallower snowpacks in the mid-elevation ranges.  This is a tough problem to recognize, and requires taking the time to dig down to do your own localized assessments, and realize that great variability can exist across a slope. It’s hard to know if and where that shallow tender trigger spot may exist.  If in doubt, play it safe.  

Avalanche Problem 2: Loose Wet
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Sunny skies, even warmer temperatures, and light winds will allow for slopes with exposure to the sun to warm and become less stable.  Watch for loose wet activity on east facing slopes in the morning, followed by south, then west in the afternoon.  Rock outcrops will warm the surounding snow even more.  While these slides are likely to be small, they could knock a person off their feet and become larger especially in the confines of a couloir.    

Avalanche Problem 3: Wind Slab
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Winds were light yesterday, with no visible snow transport reported.  Today moderate north winds are projected for the afternoon over ridge-tops.  These winds could result in snow transport and the development of small new sensitive wind slabs on leeward side of ridgelines and upper elevation terrain features.  Look for small pockets of fresh dense wind blown snow especially on E-S-W facing terrain. While small, these could be large enough to knock a rider off their feet and lead to a nasty fall.  While unlikely, a larger older wind slab may remain sensitive to a human trigger in isolated areas on other aspects.

advisory discussion

The persistent slab problem continues to be the focus of our attention and discussion.  When will we drop the hazard surrounding this issue to low?  We have had some avalanche events in the past week that are unusual for us in the Sierra, the most recent being 3 natural slides just 3 days ago that we don’t know a lot about.  What we do know is that a weak snowpack structure can be found in many areas throughout the forecast zone.  While mid-pack concerns such as buried surface hoar and mid-pack facets seem to be stabilizing, the lower snowpack, particularly in shallow areas outside of Mammoth, remains concerning.  We need more time for greater confidence.   

Weather and CURRENT CONDITIONS
weather summary

Another mostly calm sunny day is on tap, with slightly warmer temperatures than yesterday.  Light west winds over ridge-tops are expected to increase to moderate levels in the afternoon out of the north.  High temperatures will continue to increase thru the weekend as high pressure and dry conditions prevail thru the end of the month.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Friday Friday Night Saturday
Weather: Sunny. Clear. Sunny.
Temperatures: 39 to 45. deg. F. 19 to 25. deg. F. 44 to 49. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds. Gusts up to 30 mph in the morning.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Sunny. Clear. Sunny.
Temperatures: 33 to 39. deg. F. 20 to 26. deg. F. 41 to 46. deg. F.
Ridge Top Winds: West 10 to 15 mph increasing to north 20 to 30 mph in the afternoon. Gusts up to 45 mph. North 25 to 35 mph with gusts to 55 mph. Northeast 15 to 25 mph. Gusts up to 35 mph decreasing to 25 mph in the afternoon.
Expected snowfall: 0 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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