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.

The storm system that moved over the region yesterday will remain over Nevada today. For most of the forecast area, storm totals are running 5 to 7 inches with up to 13 inches of new snow in the Ebbetts Pass area. Continued moisture will spin off of the low pressure system creating upslope snow showers with an additional 1 to 4 inches of new snow expected across the forecast area today. Remote sensors are reporting air temperatures above 8,000' in the upper teens and low 20s this morning. Air temperatures are about 15 degrees colder at all elevations than what was observed 24 hours ago. Ridgetop winds have shifted to the west and decreased to light to moderate in speed. Light to moderate speed west the northwest winds are expected for today.

Observations:

Observations made yesterday afternoon on Andesite Ridge (Donner Summit area) revealed instability within the storm snow in wind loaded areas. Around 3 inches of new snow existed in the area with wind slabs up to 1 foot deep. An easily skier triggered intentional test slope slab failure occurred near treeline at 8,080' on an ENE aspect 36 to 41 degree slope. The weak layer was identified as lightly rimed lower density new snow near the bottom of the storm snow, just a few inches above the old/new snow interface. Good bonding of the new snow to the wet and unfrozen old snow surface was noted (video, photos, pit profile). Yesterday evening, observations made near Frog Lake (Carson Pass area) revealed similar conditions with the upside-down storm snow producing slab failure just a few inches above the old/new snow interface on a variety of near treeline test slopes. The greatest areas of instability were noted in near treeline terrain with wind loaded pockets up to 14 inches deep (photos, more info). Again, good bonding at the old/new snow interface was observed.

Avalanche Concerns: Storm snow

Avalanche concerns for today focus on instability occurring within the storm snow. Shifting winds and snow showers will combine to add additional new snow, likely increasing the size of already unstable slabs. Natural avalanche activity is not expected today, but widespread human triggering of avalanches is possible in recently wind loaded areas near and above treeline. This instability is most likely to occur on NW-N-NE-E aspects today, but will likely extend to recently wind loaded areas on other aspects as well. Slab depth is expected to be 1 to 2 feet deep with larger slabs possible in the far southern portion of the forecast area. The upside-down portion of lower density new snow near the bottom of the storm snow layer is expected to continue to be the main weak layer. With colder air temperatures, the wet old snow surface will slowly continue to refreeze over the next few days. This will further increase the bond strength at the old/new snow interface, at least in the short term.

The bottom line:

Near and above treeline, avalanche danger is MODERATE in recently wind loaded areas on all aspects on slopes 35 degrees and steeper. Below treeline, pockets of MODERATE danger exist on all aspects in open areas on slopes 35 degrees and steeper.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	18 to 22 deg. F.
Max. temperature in the last 24 hours:	31 to 34 deg. F.
Average wind direction during the last 24 hours:	Southwest shifting to west
Average wind speed during the last 24 hours:	40 mph
Maximum wind gust in the last 24 hours:	69 mph
New snowfall in the last 24 hours:	5 to 13 inches
Total snow depth:	95 to 144 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with numerous snow showers.	Cloudy skies with numerous snow showers.	Mostly cloudy skies with snow showers likely in the morning. A chance of snow showers in the afternoon.
Temperatures:	23 to 30 deg. F.	16 to 23 deg. F.	33 to 40 deg. F.
Wind direction:	NW	NW	NE
Wind speed:	10 to 15 mph with gusts to 25 mph.	10 to 15 mph with gusts to 30 mph.	10 to 15 mph with gusts to 30 mph in the afternoon.
Expected snowfall:	1 to 3 in.	2 to 4 in.	Up to 1 in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with numerous snow showers.	Cloudy skies with numerous snow showers.	Mostly cloudy skies with snow showers likely in the morning. A chance of snow showers in the afternoon.
Temperatures:	19 to 26 deg. F.	12 to 19 deg. F.	28 to 35 deg. F.
Wind direction:	NW	NW shifting to NE after midnight.	NE
Wind speed:	10 to 20 mph with gusts to 30 mph.	10 to 20 mph with gusts up to 35 mph.	10 to 20 mph with gusts to 35 mph.
Expected snowfall:	2 to 4 in.	3 to 5 in.	Around 1 in.