Avalanche Advisory: Monday - Jan 20, 2020

THIS AVALANCHE ADVISORY EXPIRED ON January 21, 2020 @ 6:47 am
Avalanche Advisory published on January 20, 2020 @ 6:47 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

Moderate avalanche danger exists at Upper and Middle Elevations on Northerly-Easterly aspects. Increasing Southerly winds today could produce fresh Wind slab development.  Continue to evaluate consequential terrain for residing isolated wind slabs in leeward catchment zones.

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
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    Very Large
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Shallow, fresh wind slabs may develop on NW-SE aspects with forecasted increasing southerly winds. Upper to Middle elevations will be of most concern. Previously cross loaded slopes particularly on NE & SE aspects at Tree Line have been found to harbor the deepest wind deposits from last Thursday’s storm. Evaluate carefully today for fresh wind deposits and also for isolated stubborn wind slabs, especially over exposure or terrain traps. Unsupported slopes, convex rolls, tight confined couloirs and depressions or gullies should be identified as features of concern. Look for fat pillows adjacent to ridgeline, rock outcroppings or cliff bands.

advisory discussion

Relatively light winds and warm temperatures have helped Thursday’s storm snow bond, settle, and provide much improved snow surfaces across the forecast zone. There have been no recorded or observed avalanches this weekend following the storm which averaged from 6-12” across the range. The deepest wind loaded areas have been found to be cross loaded leeward NE-SE catchment zones at Tree Line. Upper Elevations look to be much more scoured and devoid of much new snow, but there have been limited observations from high elevations and the complex nature of that terrain should always be considered when adventuring up high.

Although the winter season started out well here in regards to good snow fall and snowpack structure, those initial conditions have degraded a bit as we endured a lengthy lull in precipitation in January with violent eroding winds and strong temperature gradients that have weakened residing old snow. The snowpack currently is quite variable throughout the forecast zone with overall thin conditions to the north and south and the deepest overall totals found in the Mammoth area. A variety of crust/facet combos are present within the upper portion of the snowpack and weaker loose snow can be found around most rocky areas and shallow alpine slopes. Most of these shallow exposed alpine areas are composed of loose weaker snow encapsulated by firm wind board and slab from the extreme January winds. This past storm did not provide the weight necessary to cause a widespread natural avalanche cycle; the snowpack was a bit sensitive immediately following the storm Friday morning, but since then has been unreactive. A future big Sierra dump could see the mountains shed themselves of some of the residing structurally poor snowpack.

recent observations
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Weather and CURRENT CONDITIONS
weather summary

Warm temperatures and grey skies will prevail today with southerly winds increasing in velocity with ridge top gusts slated to reach 60mph. There is a slight chance of trace amounts of snow for this afternoon. High clouds will increase as another weak winter storm moves into the area for Tuesday. The brunt of this next system looks to be trending north, but there is a slight chance that Mono County could see 1-2” of new snow Tuesday.

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: Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%. Mostly cloudy then becoming partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 10%. Mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 45%.
Temperatures: 33 to 41. deg. F. 19 to 24. deg. F. 30 to 38. deg. F.
Mid Slope Winds: South around 15 mph with gusts to 35 mph. Southwest around 15 mph. Gusts up to 35 mph increasing to 45 mph after midnight. Southwest 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 0 in. 0 in. 60% probability up to 1 inch. 40% probability of 1 to 3 inches. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 20%. Mostly cloudy then becoming partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 15%. Mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 55%.
Temperatures: 25 to 33. deg. F. 15 to 20. deg. F. 22 to 30. deg. F.
Ridge Top Winds: South 15 to 30 mph with gusts to 45 mph. Southwest 15 to 30 mph with gusts to 50 mph. Southwest 25 to 40 mph with gusts to 65 mph.
Expected snowfall: 0 in. 0 in. 60% probability up to 1 inch. 40% probability of 1 to 3 inches. | SWE = less than 0.10 inch. 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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