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 3, 2012:


February 3, 2012 at 7:41 am

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


Forecast Discussion:


High pressure is firmly in place over the region. An air temperature inversion has set up this morning over the northern half of the forecast area. For northern areas, air temperatures above 8,000' are in the upper 20s this morning with teens below 7,000'. For southern areas, air temperatures above 8,000' are in the upper teens while areas around 7,000' are in the upper 20s. Sunny skies with maximum daytime air temperatures in the upper 20s to low 40s are forecast today for areas above 7,000'. Winds remain out of the east to northeast this morning and have become light in speed. Light winds are forecast to continue through tomorrow.

Observations:

Observations made yesterday on Relay Peak (Mount Rose area) and on Red Lake Peak (Carson Pass area) revealed more evidence of stable conditions on N-NE-E 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 (photos, pit profile, more info). With a few areas of exception, the up to 2 inches of new snow from Wednesday has been well scoured off of N-NE-E aspects in near and above treeline areas by recent NW and NE winds. The brittle rain crust covers the snow surface on N-NE-E aspects while redistributed snow exists in patches on S-SW-W aspects. There has been no evidence of unstable slab formation in wind loaded areas. Observations over the past week have noted fairly well established melt-freeze conditions on SE-S-SW aspects.

Avalanche Concerns:

Warmer air temperatures today and light winds are not expected to change the snowpack conditions that existed yesterday on N-NE-E aspects.  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 at or near the snow surface. The increased air temperatures and lighter winds will allow for more wet surface snow to form today on SE-S-SW aspects. Small amounts of roller ball activity are expected today in areas where recent new snow that has yet to under go its first melt-freeze cycle has been redistributed onto SE-S-SW aspects over the past two days. This surface instability is expected to be minimal and not pose a significant threat to backcountry travelers.


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: 18 to 28 deg. F.
Max. temperature in the last 24 hours: 28 to 35 deg. F.
Average wind direction during the last 24 hours: Northeast
Average wind speed during the last 24 hours: 36 mph
Maximum wind gust in the last 24 hours: 59 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 19 to 38 inches

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

For 7000-8000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny skies. Clear skies. Sunny skies in the morning, becoming partly cloudy.
Temperatures: 38 to 44 deg. F. 17 to 25 deg. F. 32 to 39 deg. F.
Wind direction: E Variable Variable
Wind speed: 5 to 15 mph. Light winds. Light winds.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny skies. Clear skies. Sunny skies in the morning, becoming partly cloudy.
Temperatures: 28 to 38 deg. F. 19 to 26 deg. F. 28 to 38 deg. F.
Wind direction: E Variable Variable
Wind speed: 10 to 20 mph in the morning, becoming light. Light winds. Light winds.
Expected snowfall: O in. O in. O in.