Mammoth Basin Snowpack Summary - 2015-02-11 07:00

THIS ADVISORY EXPIRED ON February 13, 2015 @ 7:00 am
Avalanche Advisory published on February 11, 2015 @ 7:00 am
Issued by Sue Burak - Inyo National Forest
Avalanche Character 1: Normal Caution
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Use normal caution when travelling in the backcountry.
Snowpack Discussion

Today’s snowpits revealed the weather history that began Friday night with colder snowfall of about 4 inches. A thick, icy, knife hard layer of rain saturated snow, 6 inches thick rain and wet snow mix that fell most of the day on Saturday and early Sunday. When temperatures cooled off Sunday night, a few inches of lighter snow and graupel fell, making a soft surface that skis well- until there is an area on the slope where the wind removed snow and left an icy surface.

As mild temperatures continue this week and the mid February sun is higher in the sky, expect the 1 to 3 inches of soft snow to form yet another crust. The icy 6 inch layer will obstruct vapor flow from beneath the crust; I expect to find facets forming under this crust in a day or so. This prominent feature will exist for the rest of the season.

There are no avalanche problems identified today. The snow surface and the rain layer will receive large amounts of the sun's energy this week. Snow surface conditions will be monitored as wet snow develops. 



recent observations

Yesterday on the Knob and in the Mammoth Lakes Basin, one to inches of soft snow and graupel provided a soft skiing surface but underneath, an incredibly thick, 6 inches of soaked, frozen, knife hard snow is the latest addition to a snowpack with multiple sun and melt freeze crusts. This layer only resembles snow in that it’s white rather than blue ice. The snow we ended up with sure is soaked!

A shovel could not cut through the layer and I broke a probe trying to get a snow depth. Aggressive snow saw work finally breached the layer. Underneath the layer is soft snow that fell Friday night before the Saturday rain and snow event.  The snowpit profile illustrates the layering in this winter’s snowpack. Stability tests lack the force to penetrate this layer.

In the Mammoth Lakes Basin above McLeod Lake, the same snow structure exists. The crucial difference is that Monday’s wind’s scoured slopes above treeline leaving alternating patches of icy slide for life conditions and soft new snow.

June Mountain reports a similar rain, soaked snow layering. During the storm, control work produced some releases on an interstorm rain layer 12” down.










CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 27 deg. F.
Max. temperature in the last 24 hours: 45 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 26 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 25 inches

The weather for the rest of the week will remain sunny with mild daytime and night time temperatures and most importantly, light winds. Temperatures may reach record highs for this time of year by the end of the week.

Expect daytime highs in the upper 40’s to 50 F at the 9,000 to 10,000 ft. elevations the next few days. Night time temperatures will gradually warm to the upper 30’s by Thursday night.  High elevations above 10,000 ft. will reach the mid 40’s and night time lows will warm to around freezing- warm for this time of year. Light east winds up to 10 mph are expected this week.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: sunny clear sunny
Temperatures: 48 deg. F. 30 deg. F. 49 deg. F.
Wind direction: E E E
Wind speed: 10 10 10
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: sun clear sun
Temperatures: 42 deg. F. 30 deg. F. 45 deg. F.
Wind direction: E E E
Wind speed: 10-15 10-15 10-15
Expected snowfall: 0 in. 0 in. 0 in.

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

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