THIS AVALANCHE ADVISORY EXPIRED ON March 20, 2016 @ 6:55 am
Avalanche Advisory published on March 19, 2016 @ 6:55 am
Issued by Andy Anderson - Tahoe National Forest

Daytime warming will create enough wet snow on sun-exposed E-SE-S-SW-W aspects for MODERATE avalanche danger to develop on slopes steeper than 35 degrees at all elevations. Loose wet snow avalanches including roller balls, pinwheels, and point releases will be possible today. Most of these loose wet snow instabilities should remain small, but some of them could entrain enough snow to pose a threat to backcountry travelers especially those that occur around terrain traps.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Last night's clear skies will have allowed the snowpack to lose enough heat for some overnight refreezing even though temperatures remained above freezing in many areas. The strong March sun and warm daytime temperatures will quickly melt through this refreeze in most areas, and deep unsupportable wet snow will form on many slopes today. The forecasted cloud cover and slightly increased winds do have the potential to slow down the melting process if they materialize. After going through several days of melt freeze cycles the snowpack has transitioned to more corn snow conditions in some areas and not in others. Once the refreeze melts, loose wet snow avalanches in the form of roller balls, pinwheels, and point releases will become possible again today especially on slopes where the wet snow exists on top of drier colder snow with less well established drainage channels. The sun exposed E-SE-S-SW-W aspects hold the best potential for loose wet avalanches. Most of the loose wet snow instabilities should remain small, but some of them could still entrain enough snow to cause problems for backcountry travelers.

Use clues like sinking into boot-top deep wet snow and smaller surface wet snow instabilities like roller balls and pinwheels to indicate that enough wet snow exists for problematic loose wet avalanches. These signs indicate that the time has come to move to more frozen slopes, move to less steep slopes, and/or switch activities for the afternoon. 

recent observations

Knee deep unsupportable wet snow had formed by noon on sun-exposed southerly aspects on Rose Knob Peak in the Mt. Rose backcountry below 8200 ft. yesterday. Above this elevation a few inches of wet snow existed above a supportable melt-freeze crust until that time. Farther south on Carson Pass daytime warming had allowed enough wet snow to form for some roller ball activity all the way up to 10,000 ft. on Round Top. Northerly aspects still held a mix of firm but cold wind packed snow and crusts above 8000 ft. in the Carson Pass area. In both the Rose Knob Peak area and the Round Top area several recent cornice failures had occurred and large cracks had formed behind many cornices that did not fail. 

Weather and CURRENT CONDITIONS
weather summary

Inversion conditions exist this morning with lower elevation sensors reporting temperatures in the upper 20's and low 30's and upper elevation sensors already showing temperatures in the mid to upper 30's. Warm dry weather will continue over the region today with daytime highs in the upper 40's to mid 50's above 7000 ft.  Some thin high cloud cover may develop over the mountains today, and the winds should increase some. After one more mostly clear night, additional cloud cover, stronger southwest winds, and a chance for some precipitation should to move into the area Sunday as a low pressure replaces the high pressure ridge. Snow levels will remain high (likely in the 8000 to 9000 ft. range) on Sunday before falling overnight on Sunday night and Monday morning. For more details on this storm check in with the Reno NWS.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 32 to 41 deg. F.
Max. temperature in the last 24 hours: 49 to 54 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 10 to 20 mph
Maximum wind gust in the last 24 hours: 36 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 78 to 116 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy with periods of sun Partly cloudy becoming clear Partly cloudy becoming mostly cloudy with isolated showers in the morning and scattered showers in the afternoon. Snow level between 8000 and 9000 ft.
Temperatures: 48 to 55 deg. F. 32 to 37 deg. F. 44 to 51 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 10 to 20 mph with gusts to 30 mph in the afternoon 10 to 20 mph with gusts to 30 mph 20 to 30 mph with gusts to 35 mph increasing to 50 mph in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy with periods of sun Partly cloudy becoming clear Partly cloudy becoming mostly cloudy with isolated showers in the morning and scattered showers in the afternoon. Snow level between 8000 and 9000 ft.
Temperatures: 40 to 48 deg. F. 30 to 35 deg. F. 34 to 44 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 15 to 25 mph with gusts to 40 mph 20 to 30 mph with gusts to 45 mph 25 to 35 mph with gusts to 55 mph increasing to 35 to 55 mph with gusts to 85 mph in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory 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.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258