Avalanche Advisory: Monday - Dec 31, 2018

THIS AVALANCHE ADVISORY EXPIRED ON January 2, 2019 @ 6:57 am
Avalanche Advisory published on December 31, 2018 @ 6:57 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

*Update - 12/31 - 1:30pm

For New Years Eve and New Years Day natural and human triggered avalanches will be unlikely. That being said there is almost always a remote possibility that small isolated wind slab avalanches are possible at upper elevations, as we were reminded yesterday (Sunday) when 2 skiers were hit by a natural avalanche. Early season obstacles exist!

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Avalanche Problem 1: Normal Caution
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While unlikely, rare small sensitive wind slabs could still linger in complex upper elevation terrain for New Years Eve and New Years Day.  2 skiers climbing the SE Gully on Mt Baldwin were caught violently by a natural wind slab avalanche on Sunday which was likely triggered by slope warming (click for details).  While NE winds will continue to blow thru New Years Day that are strong enough to transport snow (especially at upper elevations), that key ingredient, loose transportable snow, has become scarcer and scarcer over the last few days.  Strong NE winds have been blowing now since Christmas, leaving exposed slopes at mid to upper elevations highly wind effected.  These winds shifted more out of the west for a period yesterday and last night.  If you are planning on venturing into the alpine, keep in mind the remote possibility of sensitive wind slabs on any aspect, and realize that any fall could be hard to self-arrest due to the firm conditions.  

Remember to continue to practice and reinforce good travel habits such as exposing one person at a time, good communication, and carrying the right gear.  You never know when a surprise could happen.

advisory discussion

*We received a report from 2 skiers today (Monday) that they were caught in a natural wind slab avalanche yesterday while climbing the SE Gully of Mt. Baldwin.  While the avalanche danger was unlikely, this avalanche did occur in the type of terrain that the advisory mentioned would be possible for wind slabs that day.  Namely southerly facing, high elevation extreme terrain where NE winds could deposit small amounts of loose snow.  It is not know for certain, but it seems likely that yesteday's warm daytime temperatures and sunny skies warmed up sourounding rocks leading to warming of the recent wind slab resulting in it's release.  This seems especially likely as the timing of the release at 12:30pm was at the height of yesterday's daytime temperatures as well as the height of sun exposure on this SE facing terrain.   Click here for a thoughtfull detailed report from the party caught.  Thankfully they were not more seriously injured.

Although NE winds are projected to continue thru New Years Day, the colder temperatures and less and less snow available for transport will decrease the likelihood of a similar avalanche happening.  That doesn't mean that avalanches will be impossible!    

With cold temperatures and clear night-time skies persisting thru this week, the snowpack will continue to facet, especially in areas where it is particularly thin (which unfortunately is most areas).  While not a stability concern now, if and when we get substantial new snow loads, these weak layers could present a larger avalanche threat.  Keep note of how the snowpack is faceting, as well as if you see areas of feathery surface hoar persisting on top of the snow.

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*Natural avalanche sweeps 2 skiers away, leaving them bruised, partially buried, and without gear. 12/30, 12:30pm. McGee Creek - SE Gully Mt. Baldwin.

12/30 - Mammopth Lakes Basin - TJ Bowl: Warm temps, faceting snowpack.

12/30 - Mammoth - Panorama Dome: Thin snowpack, surface hoar collapsing and decomposing.

12/30 - Mammoth - Sherwins: Persisting surface hoar in sheltered areas, thin snowpack faceting.

12/30 - Mammoth - Punta Bardini: Surface hoar low in the flats, but not above, snow coverage, some small spindrifts and blowing snow over ridges.

12/29 - Lundy Canyon - Mount Scowden: Thin snowpack, facets.

Weather and CURRENT CONDITIONS
weather summary

A cold front pushing thru this morning (Monday) will lead to dropping temperatures throughout the day, light flurries in the morning, and continued NE winds (especially at upper elevations).  Expect temperatures to drop into the single digits by the afternoon and down to zero tonight even at lower elevations.  NE winds will be on the increase tonight with ridge top gusts into the 90s. 

For New Years Day expect temperatures to rebound into the mid 20s around 10,000’, sunny skies, and moderate NE ridge top winds.  

High pressure will continue to build thru the week keeping skies clear and temperatures above average.  A splitting weak low-pressure system looks to be heading our way this weekend, and models at this time are showing that the meager moisture amounts are at least favored toward the south rather than the north for a change. 

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 then becoming partly cloudy. Slight chance of snow showers through the day. Partly cloudy then becoming clear. Sunny.
Temperatures: 13 to 19. deg. F. 2 below to 3 above zero. deg. F. 21 to 26. deg. F.
Mid Slope Winds: North 10 to 15 mph with gusts to 40 mph. Northeast 10 to 15 mph with gusts to 65 mph. Light winds. Gusts up to 45 mph decreasing to 35 mph in the afternoon.
Expected snowfall: up to 1 in. 0 in. 0 in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy then becoming partly cloudy. Slight chance of snow showers. Partly cloudy then becoming clear. Sunny.
Temperatures: 9 to 15. deg. F. 1 below to 6 below zero. deg. F. 21 to 26. deg. F.
Ridge Top Winds: Northeast 15 to 30 mph with gusts to 55 mph. Northeast 25 to 40 mph increasing to 40 to 60 mph after midnight. Gusts up to 90 mph. Northeast 20 to 35 mph. Gusts up to 60 mph decreasing to 45 mph in the afternoon.
Expected snowfall: up to 1 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 Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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