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.

Today will be the last warm and sunny day for a while. After today, expect significant cloud cover and a wet weather pattern that will take a couple of days to develop. This morning, air temperatures above 7,000' as reported by remote sensors are in the low to mid 30s across the forecast area. Maximum daytime air temperatures in the 40s and 50s are expected this afternoon for areas above 7,000'. Ridgetop winds remain out of the southwest and are light to moderate in speed. Moderate speed winds are forecast to continue today before increasing to strong tomorrow and continuing into the upcoming storm cycle. For tomorrow, expect cloudy skies with a chance of light snow showers and daytime highs in the 20s and 30s.

Recent Observations:

When tracking a persistent weak layer, it is just that - persistent. Observations made yesterday at Polaris Point (Ward Canyon area) and on the East Ridge of Tamarack Peak (Mount Rose area) fell right in line with other recent observations from around the forecast area. The persistent weak layer of crusts and faceted snow that exists in the middle to lower third of the snowpack on the vast majority of NW-N-NE aspects around the forecast area continues to show weakness and the ability to propagate collapse through the snowpack (pit profiles, videos, more info). Recent east winds have scoured snow off of the very top portion of N-NE aspect avalanche start zones, but a significant slab still sits on top of the well developed persistent weak layer on the mid and lower portion of wind scoured avalanche paths and other steep slopes. On E-SE-S-SW-W aspects, wet snow existed by mid day with wet surface snow also noted in sun exposed areas on northerly aspects. No significant wet snow instability was observed.

Today's Primary Avalanche Concern: Persistent Deep Slabs

At this time, slab avalanches are difficult to trigger within the existing snowpack due in part to the strength of the overlying slab. That said, nearly all recent field data indicates that on NW-N-NE aspects the persistent weak layer of crust and facets just below the 1 to 5 foot slab of settled and cohesive mid February and early March storm snow has the necessary characteristics to propagate collapse. Add to that a trigger and a sufficiently steep slope, and a large deep slab avalanche will likely occur. Given the strength of the overlying slab, there will be a limited number of trigger points on any given slope that will allow force to penetrate through the slab and collapse the weak layer below. That suggests that a slope could be traveled by many individuals before the trigger point is loaded and an avalanche occurs. Exercise good travel habits and take a conservative approach as the consequences of becoming caught in a deep slab avalanche will be significant given the depth and density of the slab that will be involved. The current penetration depth of skis and snowmobiles will not touch or disrupt the weak layer, keeping even fully tracked out slopes suspect for future loading events such as the forecast storms this week.

Today's Secondary Avalanche Concern: Warming Instabilities

Well above freezing air temperatures will allow for wet surface snow to form once again today in sun exposed areas. Snow surface refreeze that occurred last night will melt quickly, decreasing the supportability of the snow surface. With several days of melt freeze conditions having already occurred on E-SE-S-SW-W aspects, the amount of wet snow instability that occurs today is expected to be minimal. It is only expected to pose a threat to backcountry travelers when combined with secondary terrain hazards such as cliffs or terrain traps that could magnify the consequences of becoming caught in an otherwise small and inconsequential wet loose snow avalanche.

The bottom line:

Pockets of MODERATE avalanche danger exist both above and below treeline on NW-N-NE aspects on slopes 35 degrees and steeper due to ongoing deep slab instability. The possibility of large destructive human triggered avalanches remains in these areas. For all other areas, avalanche danger is LOW.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	30 to 37 deg. F.
Max. temperature in the last 24 hours:	44 to 53 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	20 mph
Maximum wind gust in the last 24 hours:	34 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	29 to 47 inches

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

For 7000-8000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Thin high cloud cover.	Mostly cloudy skies.	Cloudy skies with a chance of snow showers.
Temperatures:	48 to 55 deg. F.	23 to 30 deg. F.	32 to 40 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	15 to 25 mph with gusts to 40 mph.	20 to 30 mph with gusts to 45 mph.	35 to 45 mph with gusts to 65 mph.
Expected snowfall:	O in.	O in.	0 to trace in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Thin high cloud cover.	Mostly cloudy skies.	Cloudy skies with a chance of snow showers.
Temperatures:	42 to 48 deg. F.	23 to 30 deg. F.	25 to 32 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	20 to 30 mph with gusts to 45 mph.	30 to 40 mph with gusts to 60 mph.	45 to 60 mph with gusts to 85 mph.
Expected snowfall:	O in.	O in.	0 to trace in.