June Mountain Area, Mammoth Basin Snowpack Summary - 2015-03-18 07:15

THIS ADVISORY EXPIRED ON March 20, 2015 @ 7:15 am
Avalanche Advisory published on March 18, 2015 @ 7:15 am
Issued by Sue Burak - Inyo National Forest
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Temperatures cool off today and for the next few days and the snow at mid and high elevations will get a good refreeze. The usual common sense advice applies for wet snow conditions; If you find yourself in unsupportable or collapsing snow at any elevation, it's time to leave.

At mid to treeline elevations, percolating water may activate buried layers of facets under the February layer or deeper in the snowpack. While alpine snowpacks are colder and drier than wet mid elevations packs, it's possible percolating melt water could reach buried facets on traditionally cold and shady aspects in the Negatives and along the Mammoth Crest. With colder temperatures expected for the next 5 to 6 days, the possibility of loose wet avalanches will decrease.

Snowpack Discussion

Nights are reaching freezing temperatures at the summits of Mammoth and June Mountains and Gem Pass but at mid elevation stations at the ski patrol study plot and Mammoth Pass, it's been 5 days since night time lows reached the freezing mark. Snow at the surface was wet and skis penetrated to the early February layer. Underneath the February layer, there were thin columns of melt water- flow fingers indicating melt water from the surface had penetrated the thick February layer though it did not progress much farther through the thin snowpack. A large whumpf startled me skiing along flat terrain on the south side of Crystal Lake yesterday.  A few loose wet slides occurred over the weekend on east facing slopes but the cloud cover and breezy northerly winds kept the snow surface cool . Yesterday was the final day of warming- cooler temperatures and north winds will lock up the snowpack until at least the first part of next week. Steep sheltered north facing high elevation terrain still has decent skiing conditions though thin wind and sun crusts appear in isolated areas on open slopes.

The change in the weather and an inch or two of snow today will improve conditions in alpine areas.

We are not alone with this extended period of mild temperatures- Bridger Bowl in Montana and the Wasatch have not seen freezing temperatures at night for many days.

recent observations

A large whumpf startled me skiing along flat terrain on the south side of Crystal Lake yesterday.  Above Crystal Lake, snow changed to a more winter-like texture though the upper layers were moist. In places the February layer collapsed on facets below the crust under the pressure of skis. A few small loose wet slides were observed below rock bands and off the crest. Even though the snow is wet at elevations up to around 9,500 ft. wet facets below thick layers and crusts lack strength. Cooling temperatures will lock up potential wet snow instability until next week.


CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 28 deg. F.
Max. temperature in the last 24 hours: 47 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 15 to 20 mph
Maximum wind gust in the last 24 hours: 45 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 18 inches

Partly sunny skies this morning will give way to clouds and scattered snow showers this afternoon. Morning temperatures are close to and below freezing at mid elevations while higher terrain had a solid refreeze. Ridgetop winds are blowing from the northeast at 15-25 mph. A few thunderstorms west of the crest are forecasted for the afternoon. Thursday will be sunny and cooler and cooler temperatures are expected until the first part of next week.

Daytime highs will reach the  mid 40's at the mid elevations and the upper 30's above 10,000 ft. Up to an inch of snow will fall at the higher elevations. Breezy north winds are expected for the next few days at all elevations.


Elev: 9500 ft.

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: partly sunny in the AM, clouds, scattered snow showers in the afternoon clouds, scattered snow showers mostly sunny
Temperatures: 45-50 deg. F. 32 deg. F. 50 deg. F.
Wind direction: NE NE NE
Wind speed: 10-15 10-15 10-15
Expected snowfall: 1 in. 1 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: partly sunny AM, clouds and snow in the afternoon clouds and snow showers partly sunny
Temperatures: 40 deg. F. 27 deg. F. 44 deg. F.
Wind direction: NE NE NE
Wind speed: 10-15 10-25 15-25
Expected snowfall: 1 in. 1 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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