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 January 20, 2011:


January 20, 2011 at 7:40 am

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


Forecast Discussion:


An air temperature inversion is in place over the forecast area this morning. Colder air from yesterday's cold front passage has kept air temperatures below freezing at all elevations overnight despite the inversion. Ridgetop winds shifted to the northeast to east yesterday and will continue today. Moderate to strong ridgetop wind speeds will continue this morning before decreasing to light to moderate this afternoon. Maximum daytime air temperatures are expected at around 10 degrees warmer than yesterday. Friday is expected to have similar daytime high temperatures as today with light to moderate northwest winds.

Observations:

Observations made yesterday in the Emerald Bay Chutes (Desolation Wilderness/Emerald Bay area) revealed a strong overnight refreeze and minimal snow surface melting. A supportable snow surface existed all day long on E-SE-S aspects between 7,000' and 9,000'. Wet snow was limited to the top 2.5 inches in the most sun exposed areas on southerly aspects with significantly less snow surface melting above 8,000'. Shaded areas on all aspects remained frozen all day (photo, more info). Areas on E-SE aspects that went into the shade during the afternoon hours quickly refroze with supportable melt freeze crust. Boot penetration throughout the area ranged from 0.5 inches in locations with minimal surface melting to 6 inches at the lowest elevation locations. No evidence of snowpack instability of any type was observed.

Avalanche Concerns:

Another strong refreeze last night and forecast air temperatures in the upper 30s to mid 40s today are expected to keep surface wet snow instabilities to a minimum. Continued NE winds today will again create some convective cooling, slowing snow surface melting on N-NE-E aspects. Most northerly aspects are likely to remain frozen all day. During the mid day and afternoon hours, very shallow and slow moving wet snow sluffs involving the top couple of inches of wet surface snow will become possible. This is expected to remain isolated to steep open areas with direct sun exposure on SE-S-SW aspects. The anticipated size of any wet snow sluffs that occur today are not expected to provide a significant hazard to backcountry travelers.

 


The bottom line:

Avalanche danger is 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: 23 to 30 deg. F.
Max. temperature in the last 24 hours: 29 to 34 deg. F.
Average wind direction during the last 24 hours: Northeast
Average wind speed during the last 24 hours: 50 mph
Maximum wind gust in the last 24 hours: 80 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 61 to 90 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: 40 to 48 deg. F. 25 to 35 deg. F. 43 to 50 deg. F.
Wind direction: E E Variable
Wind speed: Up to 10 mph. Up to 10 mph in the evening becoming light. Light winds.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Thursday: Thursday Night: Friday:
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 37 to 45 deg. F. 30 to 36 deg. F. 40 to 48 deg. F.
Wind direction: E NE NW
Wind speed: 30 to 45 mph with gusts to 60 mph. Winds decreasing to 10 to 20 mph with gusts to 30 mph in the afternoon. 10 to 15 mph with gusts to 25 mph. 10 to 20 mph with gusts to 35 mph.
Expected snowfall: O in. O in. O in.