Avalanche Advisory: Monday - Dec 30, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 31, 2019 @ 6:37 am
Avalanche Advisory published on December 30, 2019 @ 6:37 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists at Upper and Middle elevations on all Aspects with Winds Slab being of primary concern. LOW avalanche danger continues in wind protected lower elevations. Skier triggered avalanches have been occurring the past two days.

While not transpiring yet as of publishing--Avalanche Danger could reach CONSIDERABLE in the June Lake-Mono Lake area today if Lake Effect conditions produce locally heavier snow accumulations (6-10”) with upslope winds.

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
    Likely
    Possible
    Unlikely
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    Very Large
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Steep terrain with features conducive to capturing drifting snow will be of concern today for wind slab hazard. Winds have been shifty and have been moving residing low density snow and recent trace amounts (1-2” last night). After yesterday’s SW flow, winds will wrap back around to a predominant NE flow Monday. All aspects should be looked at critically as snow transport and deposition have been all over the compass rose the past four days. Yesterday there was a small skier triggered pocket in northerly terrain at tree line in the Sherwins, and on Saturday in steep NE terrain near Convict there was a skier triggered slide that ran nearly 1200ft. Look for snow surfaces that could indicate deposition vs. scouring and take note of clues such as active wind loading, shooting cracks, or hollow sounding areas. Be flexible with your route plans and do your own local assessments while travelling today.

advisory discussion

We have had predominantly northerly wind patterns of late with a day of SW wind thrown in yesterday. Wind direction switched back again last night to NE flow and will continue today into Tuesday. Trace amounts of snow were added last night to residing reservoirs of older soft transportable snow across the zone…so the bottom line is that there is material available to be moved around and deposited. The Northern part of the forecast zone from June Lake Area up to Virginia Lakes area should be given extra consideration as Christmas snowfall there exceeded anywhere else (~40cm) and then again today this zone has the potential for “Lake effect” snowfall that could produce locally higher amounts (6-10”) if weather conditions line up.

Although fairly small in nature, there have been a few skier triggered slides the past two days on northerly aspects, so it shows there is some sensitivity out there. Be on your toes and consider what your getting into. Tight, convex, or terrain with exposure should be considered carefully before committing to.

A respectable snowpack exists in the Mammoth area and high elevations of the forecast zone, but a majority of the area still has limited coverage with most backcountry riders reporting hitting obstacles and recording near misses. Patience is key for being injury free.

recent observations
Submit Snowpack Observations
Submit Avalanche Observations

12/29 – Mammoth Area – Mammoth Rock – Skier triggered pocket/shooting cracks

12/29 – June Lake Area– Chicken Wing – Snow Conditions

12/29 – Mammoth Area – Mammoth Rock Bowl– Crevasse at top of Mammoth Rock Bowl

12/29 – Independence – Onion Valley Rd – Snow Conditions report

12/28 – Convict Area– Mono Jim Peak – Skier triggered avalanche

12/28 – Mammoth Area – Mammoth Crest – N winds, wind slabs

Weather and CURRENT CONDITIONS
weather summary

Light snow showers and cloudy conditions will continue with northeasterly winds and stronger 50mph gusts. Cooler temperatures (25-31degF below 10000ft and 18-24degF above 10000ft) combined with north winds will produce some frigid wind chills so prepare accordingly. The mountains could see upwards of 2” of snow today and there is also a chance for greater snow accumulation (6-10”) in the June Lake/Mono Lake zone for lake effect snow showers and chilly upslope NE flow.

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: Cloudy. Chance of snow showers through the day. Snow levels below 7000 feet. Chance of precipitation is 50%. Mostly cloudy then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 25 to 31. deg. F. 13 to 18. deg. F. 30 to 36. deg. F.
Mid Slope Winds: Northeast 15 to 20 mph with gusts to 50 mph. Northeast 15 to 20 mph with gusts to 45 mph. North around 15 mph with gusts to 35 mph.
Expected snowfall: 60% probability up to 2 inches. 40% probability no accumulation. | SWE = less than 0.10 inch. in. No accumulation. | SWE = none. in. No accumulation. | SWE = none. in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Cloudy. Chance of snow showers through the day. Snow levels below 7000 feet. Chance of precipitation is 50%. Mostly cloudy then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 18 to 24. deg. F. 10 to 15. deg. F. 24 to 30. deg. F.
Ridge Top Winds: Northeast 25 to 35 mph with gusts to 55 mph. Northeast 20 to 35 mph with gusts to 50 mph. Northeast 15 to 30 mph. Gusts up to 45 mph decreasing to 35 mph in the afternoon.
Expected snowfall: 60% probability up to 2 inches. 40% probability no accumulation. | SWE = less than 0.10 inch. 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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