Avalanche Advisory: Thursday - Dec 6, 2018

THIS AVALANCHE ADVISORY EXPIRED ON December 7, 2018 @ 6:30 am
Avalanche Advisory published on December 6, 2018 @ 6:30 am

Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Bottom Line

How to read the advisory

While natural and human triggered avalanches are unlikely, it will not be impossible today for a person to trigger a small wind slab avalanche on the leeward side of upper ridgelines on W-N-E facing slopes. Early season obstacles exist!

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Above Treeline

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Near Treeline

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Below Treeline

Avalanche Problem 1: Wind Slab

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Up to 8” of very light density new snow has fallen over the last 48 hours with surprisingly light winds. S to SW winds strong enough to transport snow have only occurred during brief periods over the uppermost ridge-tops. While natural and human triggered avalanches are unlikely, small wind slab avalanches are not impossible. These are most likely to be found on the leeward side of high elevation ridge-tops facing W-N-E. Be on the lookout for these small patches of higher density snow above steep complex terrain where triggering a small wind slab could result in a nasty fall.

Take this time to continue to develop good travel habits such as exposing one person on a slope at a time and good clear communication to set yourself up for success when conditions become more dangerous.

advisory discussion

Last week storms brought in 2-3.5’ of snow accompanied by strong SW winds, providing a supportable, all-be-it shallow base of snow and start to the backcountry touring season with few if any underlying weak layer concerns. Sunday was a beautiful calm, cold, sunny day, which allowed wind slabs from Saturday time to bond. Multiple reports came back on Sunday of people seeing evidence of D2 wind slab avalanches which occurred mid- storm. Monday cloud cover increased as well as upper elevation winds, which transported snow in some areas and likely led to isolated small patches of fresh wind slab.

A weak low pressure system brought light snowfall and surprisingly light winds on Tuesday and Wednesday, dropping up to 8” of very light low density snow. S to SW wind strong enough to transport snow only occurred over the uppermost ridge-tops, potentially leading to very isolated small wind slabs on the leeward side of these ridges. Today, continued light flurries and light wind will not add much to the avalanche problem.

Early season obstacles exist! Plenty of rocks, logs, and tree stumps are lurking just under the surface, which has led to injury and broken equipment already. Take your time, be careful, and don’t end your season before it barely begins!

Weather and CURRENT CONDITIONS

weather summary

Up to 8” of very low density snow has accumulated slowly over the last two days with surprisingly calm winds. Light snow flurries are expected to continue thru today bringing another inch of snow along with calm winds and cool temperatures very similar to yesterday. High pressure will move in tomorrow thru the weekend before another weak low pressure system is expected for early next week bringing light snowfall and moderate ridge-top winds from the SW.

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

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

	Thursday	Thursday Night	Friday
Weather:	Mostly cloudy. Scattered snow showers.	Mostly cloudy then becoming partly cloudy. Slight chance of snow showers in the evening.	Sunny.
Temperatures:	26 to 31 deg. F.	11 to 16 deg. F.	31 to 36 deg. F.
Mid Slope Winds:	Light	Light	Light
Expected snowfall:	60% probability up to 1 inch. 40% probability of 2 to 3 inches. in.	Little or no accumulation. in.	None. in.

Over 10,000 ft.

	Thursday	Thursday Night	Friday
Weather:	Mostly cloudy. Scattered snow showers.	Mostly cloudy then becoming partly cloudy. Slight chance of snow showers in the evening.	Sunny.
Temperatures:	21 to 26 deg. F.	9 to 14 deg. F.	26 to 31 deg. F.
Ridge Top Winds:	Light	Light	Light
Expected snowfall:	60% probability up to 1 inch. 40% probability of 2 to 3 inches. in.	Little or no accumulation. in.	None. 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 Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.