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.

16-24 inches of lighter 10-14% density snow has fallen across the forecast area in the last 24 hours. This new snow brings snowfall totals since Sunday up to 37-45 inches. The winds remained strong over the last 24 hours with average speeds between 40 and 50 mph over the Sierra Crest. The winds have also been shifting direction between south and southwest over the last 24 hours. The winds should decrease some today and shift more to the south and to the southeast this afternoon. The deep low pressure off the coast of CA should push another 6-12 inches of snow into the forecast area today and tonight. Tomorrow the snow should start to taper off and the winds should decrease as a the low pressure system moves away from the area.

Observations:

Yesterday, in the Mt. Rose backcountry, layer bonding tests and observations showed that the snowpack has gained some strength, but that weaknesses still exist within the storm snow (pit profile). A 6-8 inch-deep, hard-wind-slab did fail on a 38-degree, NE-facing, wind-loaded test-slope near treeline. This slope did not fail when skiers knocked a Smart Car-sized cornice onto the slope; however, this piece of cornice did trigger a shooting crack in the slope. Adding a skier's weight to the slope after the cornice then triggered the small avalanche (photo). Other avalanche prone slopes in the area exhibited similar stubbornness. Another skier-triggered avalanche was reported below treeline just east of Munchkins outside the Alpine Ski Area boundary. This slide failed within the storm snow on a 40-degree, NW-facing slope (photos). The winds continued to transport snow onto leeward slopes all day. This morning we received a report that a natural avalanche released and covered Mt. Rose Highway near the summit on the east side of the pass. We do not have any other details.

Avalanche Concern #1:

The 16-24 inches of snow in the last 24 hours has added large, heavy wind-slabs to already wind-loaded slopes. Natural and human triggered avalanches due to failure of these wind-slabs will be likely today. Avalanches will be more widespread and much easier to trigger. In heavily wind-loaded areas these wind-slabs could easily be several feet deep and entrain, literally, tons of snow. Avalanches due to failure of these wind-slabs will likely start in last night's snow but could easily step down into the older storm snow. The shifting winds will have created fragile wind-slabs in unusual places. These wind slabs will most likely exist on wind-loaded, NW-N-NE-E aspects near and above treeline. Some pockets of wind slabs could also exist in heavily wind-loaded areas below treeline.

Avalanche Concern #2:

Shifting winds and small changes in the storm conditions have created several weaknesses within the storm snow. Natural avalanches due to failure of these storm snow weakness will be possible today, and human-triggered avalanches because of these weaknesses will be probable on any open slopes steeper than 35 degrees. Since some weaknesses still exist in the snow that has fallen since Sunday, any slides that do release could step down to these lower weaknesses.

Avalanche Concern #3:

Even though observations this week indicate that the older weak layers continue to gain strength and that deep slab avalanches are unlikely, they are not impossible in very isolated areas. With enough added weight the small layer of weak, sugary crystals that exists near the Jan. 11th crust in some areas could break. If this layer does break the resulting avalanches would be large and destructive.

The bottom line:

Near and above treeline the avalanche danger is HIGH on NW-N-NE-E aspects steeper than 35 degrees. Below treeline CONSIDERABLE avalanche danger exists on open, NW-N-NE-E aspects steeper than 35 degrees. Travel in or near avalanche terrain is not recommended today.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	16 deg. F.
Max. temperature in the last 24 hours:	23 deg. F.
Average wind direction during the last 24 hours:	Shifting between south and southwest
Average wind speed during the last 24 hours:	40-50 mph
Maximum wind gust in the last 24 hours:	106 mph
New snowfall in the last 24 hours:	16-24 inches
Total snow depth:	81-105 inches

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

For 7000-8000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:	Snow showers this morning becoming more widespread and intense this afternoon.	Snow	Snow showers
Temperatures:	22-29 deg. F.	15-22 deg. F.	20-27 deg. F.
Wind direction:	South shifting to southeast	Southeast shifting to the south	Southwest
Wind speed:	10-15 mph with gusts to 35 mph increasing to 15-20 mph with gusts to 45 mph in the afternoon	10-20 mph decreasing to 10-15 mph with gusts to 30 mph after midnight	10-20 mph with gusts to 30 mph
Expected snowfall:	3-5 in.	3-6 in.	2-4 in.
For 8000-9000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:	Snow showers this morning becoming more widespread and intense this afternoon.	Snow	Snow showers
Temperatures:	17-24 deg. F.	11-18 deg. F.	19-25 deg. F.
Wind direction:	South shifting to southeast	South	Southwest
Wind speed:	15-25 mph with gusts to 50 mph increasing to 60 mph	15-25 mph with gusts to 65 mph decreasing to 45 mph	15-25 mph with gusts to 50 mph
Expected snowfall:	3-6 in.	4-6 in.	2-5 in.