Eastern Sierra Avalanche Advisory

Snowpack summaries will replace the avalanche advisory this season. The new format will be similar to the avalanche advisory with weather, recent observations and discussion. The avalanche danger rating and avalanche roses are not included in the new format. Expect two snowpack summaries a week.... more
Avalanche Advisory published on May 2, 2014 @ 7:01am: Issued by Sue Burak - Inyo National Forest
This advisory is valid for 24 hours.
bottom line

This is the last avalanche advisory for the season. This does not mean the end of avalanches- avalanche end when the snow melts. Remember to respect complicated terrain, keep your eyes open to obvious clues, and take nothing for granted.

The avalanche danger is generally LOW today.  Expect firm spring snow conditions  this morning with mid day softening.  Watch for wet avalanche activity as the sun heats up the slopes especially around rocks and places where the snow coverage is thin. As usual, you should get out early and get home early. Be aware that sunny aspects may have a wet snow danger while shadier north facing slopes still have a dry snow avalanche danger.

How to read the advisory


Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.

avalanche danger

How to read the advisory

1. Low

Above treeline

1. Low

Near treeline

No Rating

Below treeline

This is the last avalanche advisory for the season. This does not mean the end of avalanches- avalanche end when the snow melts. Remember to respect complicated terrain, keep your eyes open to obvious clues, and take nothing for granted.

The avalanche danger is generally LOW today.  Expect firm spring snow conditions  this morning with mid day softening.  Watch for wet avalanche activity as the sun heats up the slopes especially around rocks and places where the snow coverage is thin. As usual, you should get out early and get home early. Be aware that sunny aspects may have a wet snow danger while shadier north facing slopes still have a dry snow avalanche danger.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.

weather

A ridge of high pressure will bring warm temperatures and low humidities to our area through Saturday. Temperatures will be in the 60's in the Mammoth area and mid to high 50's above 10,000 ft. Snowmelt will cause minor rises in local streams.

A low pressure area will move into the Pacific Northwest this weekend bringing increasingly windy conditions to our area starting Saturday, lasting into Monday. Southwest winds gusting 35-45 mph are likely each day, especially in the afternoons and evenings. Ridges in the Sierra could see gusts 60-80 mph. This storm is likely to bring scattered showers to the region Monday into Tuesday but precipitation amounts are not expected to be significant. 

advisory discussion

After last weekend's storm, cool temperatures and northeast winds kept the snow surface from heating up. You can still find settled powder in steep sheltered north facing couloirs. The northeast winds did create some wind affected snow along upper elevation ridges. A gradual warming trend through the week and cold temperatures at night  kept wet snow avalanche activity limited to a few east and north facing slopes. The gradual warm up this week helped stabilize the snow because after a few days of melt water getting into the storm snow, the snow becomes homogenous and a spring melt freeze cycle sets up. Spring snow conditions are the best of the season.

SPRING STATEMENT

Spring is synonymous with wet avalanches. With the sun higher in the sky and daytime air temperatures above freezing, wet avalanche activity increases. More importantly, above freezing temperatures at night add to the danger and can create unstable conditions. Wet snow avalanches can occur anytime during the spring and early summer. 

This time of year the sun is close to its maximum strength. If night time low temperatures are above freezing,  the snow warms up rapidly.  If skies are cloudy overnight, you can expect wet snow avalanche conditions by mid morning. If the snow gets a good refreeze, avalanche conditions can occur later in the day or not at all. You can use the Mammoth Mountain Ski Patrol site, http://patrol.mammothmountain.com/OtherWxStations.html or http://www.wrh.noaa.gov/mesowest/mwmap.php?map=hnx   to monitor  air temperatures throughout the forecast area.

Pinwheels and large rollers of snow are signs of increasing avalanche danger. Punching to the ground in wet, unsupportable snow is another bad sign. Wet avalanches, whether loose snow or slab, can be destructive and powerful. Moving to a different aspect with less sun exposure, and less than 25 degrees in slope angle without steeper terrain above it, or simply heading over to the local crag all represent great alternatives to getting cart wheeled around in a wet slide.  

The long range forecast is for unsettled weather in May. Spring snow storms can occur. Expect a period of snowpack instability during the storm itself, then a second cycle of avalanche activity when the sun comes out and the snow has to deal with rapdi change. New snow will be very sensitive to rapid warming and direct sunlight. Pay close attention to new snow and to the old snow surface beneath it. It can lose strength rapidly as the day progresses causing a significant increase in avalanche danger.

Cornices formed this season during the March and April storms. Even though cornices are small compared to the monster cornices that can form, a cornice fall can entrain loose surface snow or trigger deep slab avalanches. Regardless of whether a cornice triggers a larger slide or not, a falling cornice is dangerous to anyone in its path.

Thanks to everyone who donated money to support the work of the avalanche center. I would like to thank Preston Few and Ryan Floyd who provided me with snow and avalanche observations and accompanied me in the field.


ESAC Weather Page

Weather Station Links:
June Mountain Summit
Mammoth Summit
Rock Creek
CURRENT CONDITIONS  Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 35 deg. F.
Max. temperature in the last 24 hours: 63 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 15-20 mph
Maximum wind gust in the last 24 hours: 30 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 16 inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 8,000 to 10,000 ft.
  Friday Friday Night Saturday
Weather: sunny partly cloudy breezy and clear
Temperatures: 60 deg. F. 43 deg. F. 59 deg. F.
Wind direction: West SW W
Wind speed: 5-10 10-15 20-25
Expected snowfall: 0 in. 0 in. 0 in.
For above 10,000 ft.
  Friday Friday Night Saturday
Weather: sunny partly cloudy sun, windy
Temperatures: 58 deg. F. 38 deg. F. 56 deg. F.
Wind direction: W SW W
Wind speed: 5-10 10-15 25-35
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

This advisory applies only to backcountry areas outside established ski area boundaries. This advisory only describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.



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