Avalanche Advisory: Monday - Feb 24, 2020

THIS AVALANCHE ADVISORY EXPIRED ON February 25, 2020 @ 6:57 am
Avalanche Advisory published on February 24, 2020 @ 6:57 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Up to 7” of new snow fell in the southern portion of the forecast zone on Saturday, with shifting winds ideal for transporting snow at upper elevations that will continue thru today.  Avalanche danger will vary widely across the forecast region today. MODERATE avalanche danger exists at treeline and above for areas south which received the most new snow, transitioning to LOW for northern areas which received only trace amounts of new snow.  Sensitive to stubborn wind slabs and slope warming from the sun will be the greatest concerns. Evaluate new snow and terrain carefully, and avoid being on or under slopes with significant fresh wind-load especially as they warm. 

 

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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New snowfall varied greatly on Saturday across the forecast zone, with much greater amounts of 7” to the south and trace amounts to the north. NE winds during the storm shifted out of the W yesterday and are shifting back to the N and NE today gusting into the 50s at ridge tops. Where greater amounts of new snow has fallen towards the south, fresh sensitive wind slabs will likely be found just below ridgelines, sidewalls of gullies, around rocks and other cross-loaded terrain features.  Slick underlying conditions could make these slabs less likely to bond, and result in them running farther than expected.  A Natural avalanche occurred yesterday that was large enough to bury someone.  Today, human triggered avalanches are still possible, and while less likely, natural avalanches could still occur where fresh wind deposited snow is warmed by the sun and sourounding rocks. Carefully evaluate local new snowfall amounts, watch for signs such as blowing snow, and be cautious of areas with deeper wind deposited denser snow.  Be especially cautious of gully or couloir features that funnel falling snow or rocks from broad expanses, especially as slopes above warm from the sun.

 
Avalanche Problem 2: Loose Wet
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For areas that received greater amounts of fresh snow to the south, sunny skies and warm temperatures today could still trigger loose wet avalanches on E-SE-S-SW-W aspects as they warm.  Watch for signs of small rollerballs originating from rock bands as early indications that larger loose-wet avalanches could be possible.  A loose-wet avalanche could also trigger a more consequential fresh wind slab.         

 
Avalanche Problem 3: Loose Dry
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For areas south which received the most new snow on Saturday, be cautious of loose dry sloughs created from your turns on especially steep slopes that could cause you to lose control.  Slick and firm or loose faceting underlying surfaces will keep this concern existing longer than normal.

 
advisory discussion

Snow fall varied widely across the forecast zone.  The Sawmill snow sensor in the Bishop region above South Lake at 11,900’ recorded 7” of new snowfall, Rock Creek at 9600’ recorded 4”, field observations in the Mammoth Lakes Basin around 10,000’ measured ~1.5”, while snow sensors Mammoth and north recorded barely an inch.

 

Variable and slick underlying conditions abound.  A fall will be hard to self arrest in many areas, and even a small avalanche could have a very bad outcome especially with all the obstacles that exist.  Ski crampons, crampons and ice ax have become standard equipment for travel in many areas. Enjoyable turns can still be found in northerly facing protected trees which continue to harbor softer faceted snow, as well as on sunny aspects as they warm from the sun. 

recent observations
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-2/23 - Bishop Creek - Table Mountain: Natural avalanche big enough to burry someone.

-2/23 - Mammoth - Lakes Basin: New snow amounts, faceted snow.

-2/23 - Mammoth - Backside: Surface softening on sunny aspects.

-2/22 - Mammoth Lakes Basin:  New snowfall and winds.

Weather and CURRENT CONDITIONS
weather summary

A blocking rIdge of high pressure will keep things sunny and dry thru the end of the week with above average temperatures.  For today expect NW to N to NE winds gusting up to 50mph+ over ridge tops, with lighter winds projected for the southern reaches of the forecast zone.  Highs are expected to reach 40°F around 10,000’.    

 

A cold front is projected to impact the Pacific Northwest this weekend, bringing increased winds for us on Saturday with chances of light snow on Sunday. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 38 to 48. deg. F. 22 to 28. deg. F. 41 to 51. deg. F.
Mid Slope Winds: Light winds becoming northwest around 15 mph in the afternoon. Gusts up to 35 mph. Northwest around 15 mph in the evening becoming light. Gusts up to 35 mph. Light winds. Gusts up to 45 mph decreasing to 30 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 29 to 37. deg. F. 19 to 25. deg. F. 32 to 40. deg. F.
Ridge Top Winds: Northwest 20 to 30 mph with gusts to 50 mph. North 25 to 35 mph with gusts to 55 mph decreasing to 15 to 30 mph with gusts to 40 mph after midnight. North 15 to 30 mph. Gusts up to 55 mph decreasing to 40 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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