Avalanche Advisory: Sunday - Mar 15, 2020 | Eastern Sierra Avalanche Center

THIS AVALANCHE ADVISORY EXPIRED ON March 16, 2020 @ 6:50 am
Avalanche Advisory published on March 15, 2020 @ 6:50 am

Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Bottom Line

HIGH avalanche danger exists today at mid to upper elevations where up to a foot of new snow has fallen overnight, and another 6-12” is likely thru today as VERY strong SW winds continue to build sensitive wind slabs. Natural and human triggered avalanches plenty large enough to bury a person will be likely in wind deposited areas. Concern will be greatest, but is not limited to, NW-NE-SE facing slopes. Human triggered storm slabs and loose dry avalanches will be of concern in steep wind-sheltered terrain as well. Be conservative, and especially avoid traveling on or under slopes with potentially wind deposited snow.

Avalanche danger will be lower south of Mammoth where less new snow is expected.

4. High

Above Treeline

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

Near Treeline

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

3. Considerable

Below Treeline

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Avalanche Problem 1: Wind Slab

Type ?
Aspect/Elevation ?
Likelihood ?

Certain

Very Likely

Likely

Possible

Unlikely
Size ?

Historic

Very Large

Large

Small

Significant new snow and very strong winds gusting into the 80s over ridgelines have built and will continue to build dangerous fresh sensitive wind slabs throughout today at mid and upper elevations, and in lower elevations that are exposed to the wind as well. While SW is the predominant wind direction, terrain below ridge lines can cause strong winds to blow any direction and deposit snow in unpredictable locations. Watch for signs such as blowing snow, cornice formation, shooting cracks and denser snow deposits to help you avoid being on or under slopes where dangerous wind slabs may exist. A questionable weak underlying snowpack exists in many areas, and a large wind slab avalanche could be enough to step down into old snow layers and result in a much larger than expected avalanche.

Avalanche Problem 2: Storm Slab

Type ?
Aspect/Elevation ?
Likelihood ?

Certain

Very Likely

Likely

Possible

Unlikely
Size ?

Historic

Very Large

Large

Small

In wind sheltered areas, storm slabs will continue to build throughout the day as more snow continues to fall. While lower elevation wind sheltered terrain will provide safer travel, do your own local stability assessments before entering steeper more consequential terrain. Convex rolls are likely trigger points and even small slides that end in a gully or depression could bury you.

Avalanche Problem 3: Loose Dry

Type ?
Aspect/Elevation ?
Likelihood ?

Certain

Very Likely

Likely

Possible

Unlikely
Size ?

Historic

Very Large

Large

Small

Making turns in steep wind sheltered terrain could easily cause loose dry sloughing that could sweep you off your feet and drag you into obstacles and result in injury or worse, especially if the slope ends in a terrain trap such as a gully or depression.

advisory discussion

And remember, a shallow snowpack with many obstacles existed yesterday before this new snow!! Sharks in the form of rocks, stumps and logs are lurking just below this new snow surface!

recent observations

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Snow / Water Totals for Mammoth pass: 1.6" SWE (snow water equivalent) overnight!

-3/14 - Mammoth Lakes Basin - Red Cone: New snow and winds.

-3/14 - Southern Sierra: High winds - snow transport.

-3/14 - Mammoth - Minaret Vista: New snow and snowpack.

-3/14 - Mammoth - Smugglers: Snowpack.

Weather and CURRENT CONDITIONS

weather summary

The strongest winter storm of the year is upon us. 1-2ft of total new accumulation is expected by the end of the day today, with another 6-10” tonight for Mammoth area north, with less expected further south. Very strong SW winds will continue gusting into the 70mph range over ridgetops, High temperatures are expected in the mid 20s F around 10,000’.

This storm will continue to bring heavy snow thru Monday, with light snow possible thru Tuesday. Temperatures will be below average thru the rest of the week.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS

For 8,000 ft. to 10,000 ft.

	Sunday	Sunday Night	Monday
Weather:	Mostly cloudy. Chance of snow. Snow levels below 7000 feet. Chance of precipitation is 65%.	Mostly cloudy. Snow in the evening, then chance of snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 70%.	Mostly cloudy. Snow likely in the morning, then snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 85%.
Temperatures:	26 to 34. deg. F.	19 to 25. deg. F.	26 to 34. deg. F.
Mid Slope Winds:	South 25 to 35 mph with gusts to 60 mph.	South 15 to 25 mph with gusts to 45 mph.	South 15 to 20 mph with gusts to 35 mph.
Expected snowfall:	70% probability of 3 to 8 inches. 30% probability of 8 to 14 inches. \| SWE = 0.20-0.45 inch. in.	80% probability of 3 to 8 inches. 20% probability of 8 to 12 inches. \| SWE = 0.20-0.45 inch. in.	90% probability of 3 to 8 inches. 10% probability of 8 to 12 inches. \| SWE = 0.20-0.45 inch. in.

Over 10,000 ft.

	Sunday	Sunday Night	Monday
Weather:	Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 75%.	Mostly cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 80%.	Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 90%.
Temperatures:	19 to 25. deg. F.	13 to 18. deg. F.	19 to 25. deg. F.
Ridge Top Winds:	Southwest 30 to 50 mph with gusts to 70 mph.	South 25 to 40 mph with gusts to 55 mph.	South 15 to 30 mph with gusts to 45 mph.
Expected snowfall:	70% probability of 3 to 8 inches. 30% probability of 8 to 14 inches. \| SWE = 0.25-0.50 inch. in.	80% probability of 3 to 8 inches. 20% probability of 8 to 12 inches. \| SWE = 0.25-0.50 inch. in.	90% probability of 3 to 8 inches. 10% probability of 8 to 12 inches. \| SWE = 0.25-0.50 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.