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 change in the weather will occur today as cloud cover moves into the forecast area ahead of a significant storm system expected to affect the forecast are tonight through Wednesday. Air temperatures at the upper elevations are several degrees warmer this morning after winds shifted from east to southwest overnight. Ridgetop wind speeds are expected to increase as the day progresses.

Observations: 

Observations made yesterday continued the trend of the past few days of a wide variance in snowpack instability from one area to another. On Donner Summit, continued instability in heavily wind loaded areas on NW-N aspects at around 7,600' occurred at the base of the recent storm snow. Skier triggered shooting cracks up to 35' long and 2.5 feet deep with a few loud whumpfing noises associated with the collapse and cracking occurred in these areas. On Silver Peak (Pole Creek area) continued wind loading on N aspects just above treeline at 7,800' allowed for much smaller and shallower skier triggered cracking. In this area the slab depth was 6 inches or less and shooting cracks were less than 10 feet long with failure occurring at the base of the recent storm snow (video). Also in this area, large widespread areas of 1 cm surface hoar were observed in large near treeline open areas on N-NE aspects just below ridgelines (photos). At mid day yesterday, these areas showed no signs of becoming destroyed by sun or wind. On Jake's Peak (West Shore Tahoe area), observant skiers reported no evidence of instability whatsoever in near treeline and below treeline terrain on N-NE aspects between 6,800' and 9,200'.

Avalanche Concerns:

Avalanche concerns for today focus on lingering slabs of recently wind loaded snow mainly in near treeline areas on NW-N-NE aspects. Most above treeline areas were well scoured yesterday by E winds, but a few lingering pockets may remain. Existing areas of surface hoar are a concern with snowfall expected tonight. Warmer air temperatures today than yesterday will help to destroy these crystals. If you are out this afternoon and see areas of surface hoar surviving, please submit your observations this evening. The more detail you can convey about the terrain, the more meaningful your observation will be to this advisory tomorrow.

 

The bottom line:

Near and above treeline, pockets of MODERATE danger linger in recently wind loaded areas on NW-N-NE aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW in wind protected areas. Increasing avalanche danger is expected overnight into Wednesday.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	25 to 31 deg. F.
Max. temperature in the last 24 hours:	31 to 33 deg. F.
Average wind direction during the last 24 hours:	East shifting to southwest
Average wind speed during the last 24 hours:	30 mph
Maximum wind gust in the last 24 hours:	69 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	67 to 105 inches

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

For 7000-8000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Cloudy skies with a chance of snow in the afternoon.	Cloudy skies with snow.	Cloudy skies with snow in the morning. Snow likely in the afternoon.
Temperatures:	29 to 36 deg. F.	17 to 24 deg. F.	27 to 34 deg. F.
Wind direction:	S shifting to SW	S	SW
Wind speed:	Around 10 mph in the morning increasing to 15 to 20 mph with gusts to 35 mph in the afternoon	15 to 25 mph with gusts to 40 mph.	15 to 25 mph with gusts to 45 mph.
Expected snowfall:	0 to trace in.	4 to 8 in.	2 to 4 in.
For 8000-9000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Cloudy skies with a chance of snow in the afternoon.	Cloudy skies with snow.	Cloudy skies with snow in the morning. Snow likely in the afternoon.
Temperatures:	25 to 32 deg. F.	15 to 22 deg. F.	27 to 33 deg. F.
Wind direction:	S shifting to SW	SW	SW
Wind speed:	10 to 15 mph with gusts to 30 mph in the morning. Winds increasing to 20 to 30 mph with gusts to 60 mph in the afternoon.	25 to 35 mph with gusts to 70 mph.	20 to 30 mph with gusts to 60 mph. Gusts decreasing to 45 mph in the afternoon.
Expected snowfall:	0 to trace in.	5 to 9 in.	3 to 5 in.