Avalanche Advisory: Saturday - Jan 23, 2021 | Eastern Sierra Avalanche Center

THIS AVALANCHE ADVISORY EXPIRED ON January 24, 2021 @ 6:14 am
Avalanche Advisory published on January 23, 2021 @ 6:14 am

Issued by Steve Mace - ESAC

Bottom Line

How to read the advisory

LOW avalanche danger persists at all elevations today. Minimal amounts of fresh snow and shifting winds have renewed the potential for thin reactive wind slabs on all aspects near and above tree line. If snow totals outperform the forecast today we can expect the avalanche hazard to rise as well. The extremely thin coverage, variable surface conditions, and a plethora of freshly hidden obstacles remain the greatest hazards to backcountry enthusiasts.

1. Low

Above Treeline

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

1. Low

Near Treeline

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

1. Low

Below Treeline

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

Avalanche Problem 1: Wind Slab

Type ?
Aspect/Elevation ?
Likelihood ?

Certain

Very Likely

Likely

Possible

Unlikely
Size ?

Historic

Very Large

Large

Small

Less than 2” of low-density snow accumulated yesterday and there is a chance of continued snowfall today bringing another ~2”~ of snow to the forecast area. Moderate to strong SW winds dominated yesterday however the winds will shift to the north today and may work to redistribute yesterday’s small amounts of snow to more southerly aspects. Be on the lookout for shallow and reactive wind slabs on all aspects near and above treeline. Identify terrain features that are conducive to capturing wind transported snow. Leeward sides of ridgelines, cliff bands, and cross-loaded guile features all deserve evaluation. Windspeeds today are likely to be right in the prime range for slab development. (20-60mph) However, it is worth considering the very shallow nature of our snowpack and the minimal amount of fresh snow available for transport when evaluating the potential for reactive wind slabs today. Prior to this storm most southerly aspects within our forecast area were either completely dry or containing minimal amounts of snow, making travel in these areas unrealistic. In addition, more northerly terrain has been dominated by thin coverage and a variety of hard and slick surfaces. While sizable wind slabs are not likely today, even a small and shallow pocket of unstable snow might be enough to knock you off your feet leading to a very unpleasant fall.

advisory discussion

While the minimal amounts of fresh snow were not enough to change the overall stability, it has brought about a new set of considerations for backcountry travelers. Prior to this storm surface conditions were extremely variable. Wind etched sastrugi and wide swaths of bare ground dominate much of the alpine while many areas below treeline present the backcountry enthusiast with a plethora of obstacles and a variety of challenging melt-freeze crusts. Some more exposed and shaded areas that have held slidable snow before this storm presented a very hard and slick surface. Even a small and shallow pocket of unstable snow in these areas might be enough to knock you off your feet and lead to a nasty fall through unpleasant terrain. Furthermore, a fresh coat of thin snow will now be hiding previously visible obstacles from view, while not providing enough cover to avoid hitting them. It will be important to remain vigilant and consider your exposure to this wide range of obstacles as you travel in the backcountry today.

recent observations

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1/22- Virginia lakes- Thin coverage and fresh snow in Virginia lakes

1/22- Mt Whitney- Minimal snow coverage

1/21- Mammoth Area- Snow conditions in the Lakes Basin

1/21- Mammoth Area- Snow conditions, Red cone ridge

1/21- Mammoth Area-Snow conditions, Hammil bowl

1/21- Mammoth Area- Thin and variable snow conditions, San Joaquin ridge

Weather and CURRENT CONDITIONS

weather summary

Expect mostly cloudy skies today with a chance of snow throughout the day. Snowfall totals are likely to be minimal today with a chance of up to 2” of snow near the crest. Temperatures will stay well below freezing today as the winds shift to the north. Light mid-slope winds will increase to moderate speeds today with ridge top gusts around 40 mph.

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

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

	Saturday	Saturday Night	Sunday
Weather:	Mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 45%.	Mostly cloudy then becoming partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 15%.	Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%.
Temperatures:	21 to 29. deg. F.	9 to 15. deg. F.	25 to 33. deg. F.
Mid Slope Winds:	Light winds becoming north 15 to 20 mph with gusts to 40 mph in the afternoon.	North 15 to 20 mph with gusts to 35 mph in the evening becoming light.	Light winds becoming southwest around 15 mph in the afternoon. Gusts up to 30 mph.
Expected snowfall:	80% probability up to 2 inches. 20% probability of 2 to 4 inches. \| SWE = less than 0.10 inch. in.	100% probability up to 1 inch. \| SWE = trace amounts. in.	0 in.

Over 10,000 ft.

	Saturday	Saturday Night	Sunday
Weather:	Mostly cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 50%.	Mostly cloudy then becoming partly cloudy. Slight chance of snow in the evening. Snow levels below 7000 feet. Chance of precipitation is 15%.	Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%.
Temperatures:	14 to 20. deg. F.	4 to 9. deg. F.	17 to 23. deg. F.
Ridge Top Winds:	North 15 to 25 mph. Gusts up to 25 mph increasing to 35 mph in the afternoon.	North 15 to 25 mph with gusts to 35 mph.	West 15 to 20 mph with gusts to 30 mph.
Expected snowfall:	80% probability up to 2 inches. 20% probability of 2 to 4 inches. \| SWE = less than 0.10 inch. in.	100% probability up to 1 inch. \| SWE = trace amounts. 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.