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.

A strong east wind event began yesterday afternoon and peaked during the overnight hours. Ridgetop wind speeds peaked around 10 to 11pm last night and have been on a steady decrease ever since. Winds remain moderate in speed this morning. Wind direction has shifted slightly from east northeast to east. Winds are forecast to remain out of the east today and continue to gradually decrease in speed as the day progresses. Significant cooling occurred overnight and brought air temperatures at 8,500' down into the single digits. Warmer air is starting to move into the region with some upper elevation remote sensors already showing several degrees of warming this morning. An air temperature inversion is also strengthening with continued cooling on mountain valley floors. Sunny skies and gradually warming air temperatures are forecast for the next couple of days.

Observations:

Observations made yesterday on Carpenter Ridge (Independence Lake area) and on Red Lake Peak (Carson Pass area) revealed mostly stable snowpack conditions. Wind transport of recent storm snow was observed in above treeline areas, especially during the afternoon hours. Blowing snow was noted to remain suspended in the air and was carried off of the peaks rather than deposited in the lee areas on the opposite side of the ridges. No new pockets of wind loading or unstable wind slab formation were observed yesterday (pit profile, photos, more info). Wind scoured surfaces exist near and above treeline on NE-E aspects. Below treeline and in other east wind and sun protected areas near treeline, 8 to 20 inches of unconsolidated snow, often topped with surface hoar existed in most areas above 7,000'.

Primary Avalanche Concern: Wind Slabs

While no evidence of new wind slab formation was found yesterday, evidence of unstable wind slabs were observed Monday in the West Shore Tahoe and Bear Valley areas (photos, pit profiles, more info). With the addition of wind speeds reaching their maximum during the past 12 hours, the possibility of isolated pockets of wind loading and subsequent instability cannot be ignored. Most of the blowing snow last night is expected to have followed the observations from yesterday afternoon, remaining suspended in the air rather than depositing in lee areas. However, some wind loading and wind slab formation may have occurred overnight in very isolated areas on steep SE-S-SW-W-NW aspects. With wind speeds already decreasing this morning and forecast to continue to decrease through today, no additional wind transport of snow is expected.

 

The bottom line:

For most locations near and above treeline avalanche danger is LOW. Very isolated pockets of MODERATE danger may exist near and above treeline on SE-S-SW-W-NW aspects, 37 degrees and steeper. Below treeline, avalanche danger is LOW for all elevations and aspects.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	9 to 16 deg. F.
Max. temperature in the last 24 hours:	19 to 26 deg. F.
Average wind direction during the last 24 hours:	East northeast
Average wind speed during the last 24 hours:	56 mph
Maximum wind gust in the last 24 hours:	87 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	62 to 90 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Sunny skies.	Clear skies.	Sunny skies.
Temperatures:	25 to 32 deg. F.	14 to 22 deg. F.	33 to 40 deg. F.
Wind direction:	E	E	NE
Wind speed:	10 to 15 mph with gusts to 40 mph. Gusts decreasing to 30 mph in the afternoon.	Around 10 mph with gusts to 20 mph.	10 to 15 mph with gusts to 25 mph.
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Sunny skies.	Clear skies.	Sunny skies.
Temperatures:	20 to 27 deg. F.	20 to 26 deg. F.	29 to 36 deg. F.
Wind direction:	E	E	NE
Wind speed:	30 to 45 mph with gusts to 60 mph in the morning. Winds decreasing to 20 to 30 mph with gusts to 45 mph in the afternoon.	20 to 30 mph with gusts to 50 mph.	20 to 30 mph with gusts to 50 mph.
Expected snowfall:	O in.	O in.	O in.