Mammoth Basin Snowpack Summary - 2015-03-13 07:15

THIS ADVISORY EXPIRED ON March 16, 2015 @ 12:15 am
Avalanche Advisory published on March 13, 2015 @ 7:15 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

Yesterday was the first day of significant warming as the high pressure ridge begins to build over California. After five days of cool daytime temperatures in the mid 30’s with cool to cold nights, high elevation north facing slopes that escaped the brunt of the north winds slopes at upper elevations got a rude surprise today when strong sun heated the air to temperatures 10 to 15 degrees warmer than Tuesday. Daytime temperatures were 10 degrees warmer at Gem, 15 degrees warmer at the Mammoth Pass installation and at the Ski Patrol Study plot.  Areas on slopes where new snow had accumulated settled rapidly yesterday.

Over the next few warm days, you are mostly like to find wet snow issues on steep, east through SE facing aspects below 10,000 ft. These aspects have already seen some warming and this time of year, it takes only a few days for the sun to destabilize east to southeast facing slopes.  Avoid steep slopes anywhere the snowpack is soggy or the surface becomes wet with daytime heating

In high elevation north facing terrain, the last week or so of high pressure changed the shape of the snow near the surface into faceted grains that do no bond well. Any snow that feels like loose powder is actually these faceted crystals. It’s still winter up high and the little bit of snow that fell will soon change into near surface faceted grains. This weak is not a problem until a more real storm comes in and the layer is buried.    

recent observations

Observations made yesterday at mid elevations in the Mammoth Lakes Basin continue to show a snowpack in various stages of transition to spring. There are more patches of bare ground, melt freeze crusts were supportable in the morning and softened by mid-day.

In north facing alpine terrain alpine terrain from the Red Cone to TJ Bowl areas, wind deposits up to 2 inches were scattered along the landcape. The combination of southwest winds during what passes for a storm this year and post frontal north winds blew what little snow fell into scallop textured surfaces in exposed areas. Stability test results showed wind affected snow was bonded to the early March snowfall that is now rounded and faceted. This snow is well bonded to the early February rain/dense snow layer.

A frozen flow finger was found at a 9,400 ft. pit dug south of Lake Mary. Flow fingers allow water to move down through the pack, pooling at texture changes in the snowpack.




Frozen flow finger at 9,400 ft. Water will be moving through the snowpack at mid elevations this weekend.


CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 25 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 50 mph
Maximum wind gust in the last 24 hours: 85 mph
New snowfall in the last 24 hours: 1-2 inches
Total snow depth: 22 inches

High pressure will keep its death grip over the West through the weekend. Winds will pick up over the weekend as another weak storm passes to the north. Winds will shift to the south and southeast today, causing temperatures to warm another few degrees in the mountains. On Sunday, ridgetop winds will increase to the 40-50 mph range as yet another stronger and more moisture laden storm passes to the north.

Skies will be mostly sunny today and tomorrow. Daytime highs reach the 50’s at the 9,000 to 10,000 ft. elevations and the mid 40’s above 10,000 ft. Slight to moderate northerly winds will keep snow surfaces cool in alpine terrain.  

While no major atmospheric river type storms appear likely next week, there's a chance we could see one or two days of scattered showers and perhaps a thunderstorm. Low forecast confidence and hard to pinpoint which days, but something to note. Welcome to spring.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Friday Friday Night Saturday
Weather: sunny mostly cloudy partly sunny
Temperatures: 52 deg. F. 39 deg. F. 52 deg. F.
Wind direction: East South Southwest
Wind speed: 10 5-10 5-10
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Friday Friday Night Saturday
Weather: Sunny mostly cloudy partly sunny
Temperatures: 46 deg. F. 30 deg. F. 46 deg. F.
Wind direction: NE SW SW
Wind speed: 10-15 50-10 10-15, gusts to 25mph
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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