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 low pressure system is passing through the forecast area today. Expected new snowfall amounts increased significantly last night with 8 to 12 or more inches now possible today, especially north of Hwy 50. Light snow showers have begun early this morning with snowfall intensity expected to increase during the morning hours. Heavy bands of snowfall could set up in isolated areas this morning, allowing for over a foot of new snow to accumulate. Remote sensors above 7,000' are reporting air temperatures in the mid teens to low 20s this morning. Reinforcing cold air arriving with the storm system will cool air temperatures a few degrees during the day in most locations. Ridgetop winds remain out of the southwest this morning and have become light in speed. Winds are expected to increase to moderate in speed with the arrival of the front this morning. Snowfall is expected to taper to scattered showers tonight. A break in the weather will occur tomorrow before another storm system impacts the forecast area on Wednesday.

Recent Observations:

Observations made yesterday just south of Red Lake (Carson Pass area) and on Tamarack Peak (Mount Rose area) matched well with other observations made around the forecast area this past week (pit profiles, videos, photos, more info). Along the Sierra Crest, the persistent weak layer of crusts and facets that exists on NW-N-NE aspects both above and below treeline within the upper half to third of the snowpack remains weak. The overlying slab of old storm snow from the Valentine's Day storm cycle is thin and brittle and not conducive to propagation of weak layer collapse. With the addition of a new load and overlying slab, this layer is likely to reactivate and become unstable. In the Mount Rose portion of the Carson Range, this layer within the snowpack is not nearly as well developed and has gained significant strength. Unlike along the Sierra Crest, the snowpack in this area is in good condition to handle new snow loading, with any snowpack failure expected to occur at of above the old/new snow interface rather than within the old snow. Well established melt freeze conditions exist on SE-S-SW aspects, so snow accumulating on these aspects today will sit on top of high density crust and ice.

Today's Primary Avalanche Concern: Storm Slabs

Light to moderate speed wind is expected to limit the amount of wind loading today, leading to similar snowfall accumulation both above treeline and in open areas below treeline. With limited wind loading to form slabs, instability today will focus any on weak layers that form within the storm snow. Instability is expected to increase through the morning hours as new snow accumulates. If weak layers do not form within the new snow today, loose snow avalanche activity will be more common than slab avalanche activity.

Today's Secondary Avalanche Concern: Persistent Deep Slabs

As new snow accumulates and adds additional load to the snowpack, the persistent weak layer of crusts and facets that exists within the upper half to third of snowpack may reactivate and become unstable today. Observations made around the forecast area over the past week have shown that this weak layer is most well developed on NW-N-NE aspects both above and below treeline along the Sierra Crest. Failure of the snowpack along this weak layer could allow for slab avalanche activity involving slabs 1 to 3 feet thick that are composed of both new and old snow. Any instability clues such as snowpack collapse or shooting cracks that are observed today are likely indicators of failure of this persistent weak layer, especially in areas where slab formation within the new snow seems minimal.

The bottom line:

Both above and below treeline, avalanche danger will rise to MODERATE today on NW-N-NE aspects on slopes 35 degrees and steeper. Pockets of CONSIDERABLE danger are possible on these slopes in areas that meet or exceed the upper end of forecast snowfall amounts. On E-SE-S-SW-W aspects, areas of MODERATE avalanche danger will form on slopes that held sufficient old snow to cover snowpack anchors prior to today's snowfall.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	16 to 20 deg. F.
Max. temperature in the last 24 hours:	26 to 36 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	10 mph
Maximum wind gust in the last 24 hours:	28 mph
New snowfall in the last 24 hours:	0 to trace inches
Total snow depth:	21 to 33 inches

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

For 7000-8000 ft:
	Monday:	Monday Night:	Tuesday:
Weather:	Cloudy skies with snow.	Mostly cloudy skies with scattered snow showers in the evening.	Partly cloudy skies, becoming mostly cloudy.
Temperatures:	18 to 24 deg. F.	3 to 10 deg. F.	24 to 30 deg. F.
Wind direction:	SW shifting to W	W	SW
Wind speed:	15 to 25 mph with gusts to 40 mph. Gusts decreasing to 30 mph in the afternoon.	15 to 20 mph with gusts to 30 mph.	15 to 20 mph with gusts to 30 mph, increasing to 30 to 35 mph with gusts to 50 mph in the afternoon.
Expected snowfall:	6 to 10 in.	0 to trace in.	O in.
For 8000-9000 ft:
	Monday:	Monday Night:	Tuesday:
Weather:	Cloudy skies with snow.	Mostly cloudy skies with scattered snow showers in the evening.	Partly cloudy skies, becoming mostly cloudy.
Temperatures:	9 to 17 deg. F.	3 to 10 deg. F.	13 to 20 deg. F.
Wind direction:	SW shifting to W	W	W shifting to SW
Wind speed:	25 to 30 mph with gusts to 45 mph, shifting and decreasing to 15 to 20 mph with gusts to 30 mph in the afternoon.	15 to 20 mph with gusts to 30 mph.	20 to 25 mph with gusts to 40 mph, shifting and increasing to 35 to 40 mph with gusts to 60 mph in the afternoon.
Expected snowfall:	8 to 12 in.	0 to trace in.	O in.