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.


This Avalanche Advisory was published on February 2, 2012:


February 2, 2012 at 7:36 am

Avalanche danger remains LOW for all elevations and aspects. Normal caution is advised.


Forecast Discussion:


Yesterday's weather system kept lingering snow showers over the higher terrain through much of the day, but still left only a trace to 2 inches of new snow across the region. Cloud cover finished moving out of the area last night. High pressure will continue to build over the forecast area today.  Remote sensors are reporting air temperatures above 7,000' mostly in the 20s this morning with increasing northeast winds. Maximum air temperatures are expected to reach into the low to mid 30s today for most areas above 7,000'. Some low to mid 40s are possible around 7,000' in the far southern portion of the forecast area. Moderate speed northeast winds are expected to build through this afternoon before decreasing late tonight. Sunny skies, light winds, and slightly warmer air temperatures are forecast for tomorrow.

Observations:

Observations made yesterday on Silver Peak (Pole Creek area) revealed stable conditions on northerly aspects, similar to other recent observations from across the forecast area. The lower and middle portions of the snowpack remain quite strong while near surface faceting processes are weakening the upper portion of the snowpack. The rain crust that formed after the January 26 rain event exists at or near the snow surface and continues to facet, becoming increasingly brittle. The up to 2 inches of new snow from yesterday did not form any significant slabs on top of this crust facet layer, even in wind loaded areas. By mid day, NW winds wrapping around the peak were noted to scour new snow off of the top of the rain crust on northerly aspects and redistribute that snow onto southerly aspects. Observations over the past week have noted fairly well established melt-freeze conditions on SE-S-SW aspects.

Avalanche Concerns:

Avalanche concerns for today are minimal. While some amount of wet surface snow will form today on SE-S-SW aspects, it is expected to remain fairly limited. Lower elevation areas with protection from NE winds will see the most melting while upper elevation areas with significant exposure to NE winds may not melt at all. The overall stable snowpack on northerly aspects is expected to keep avalanche activity unlikely due to the lack of any significant slabs overlying the weaker faceted snow and rain crust near the snow surface.


The bottom line:

Avalanche danger remains LOW for all elevations and aspects. Normal caution is advised.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature: 20 to 28 deg. F.
Max. temperature in the last 24 hours: 26 to 34 deg. F.
Average wind direction during the last 24 hours: West shifting to east
Average wind speed during the last 24 hours: 33 mph
Maximum wind gust in the last 24 hours: 56 mph
New snowfall in the last 24 hours: Trace to 1 inches
Total snow depth: 19 to 38 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:

  Thursday: Thursday Night: Friday:
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 30 to 37 deg. F. 19 to 27 deg. F. 32 to 39 deg. F.
Wind direction: NE E E
Wind speed: 20 to 30 mph with gusts to 45 mph. 15 to 25 mph with gusts to 35 mph. 10 to 15 mph.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Thursday: Thursday Night: Friday:
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 29 to 33 deg. F. 25 to 28 deg. F. 30 to 34 deg. F.
Wind direction: NE NE NE
Wind speed: 25 to 35 mph with gusts to 50 mph. 15 to 25 mph with gusts to 40 mph. 10 to 15 mph in the morning, becoming light.
Expected snowfall: O in. O in. O in.