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.

Snow showers developed overnight bringing new snow amounts of 1 to 4 inches across the forecast area. Air temperatures fell well below freezing last night with air temperatures above 7,000' in the upper 20s to mid teens. As snow showers end this morning and cloud cover decreases today, maximum daytime air temperatures will warm into the 30s and 40s. Ridgetop winds are moderate in speed out of the southwest this morning. Wind speed is forecast to increase slightly today and become strong tonight. Cloudy skies with more light snow shower activity is expected for tomorrow.

Recent Observations:

Wet surface snow remained widespread again yesterday with a poor overnight refreeze and well above freezing air temperatures affecting snow on all aspects. Several ski cuts placed below treeline around 7,500' on N aspect 40 degree test slopes in Ward Canyon produced no wet surface snow instability, despite 6 inches of ski penetration into wet snow. A solid refreeze last night is expected to have created a supportable snow surface this morning in most areas that may last through the mid day hours.

Snowpit data was collected yesterday at Polaris Point (Ward Canyon area). At this location around 7,700' on a NE aspect near treeline, increasing moisture, rounding, and strengthening of the persistent weak layer of crusts and facets that exist about 4 feet below the snow surface was observed. Propagation tests performed on the persistent weak layer at this location indicated that propagation was now unlikely (pit profile). This is very similar to snowpit data collected two days ago in similar terrain on Silver Peak (Pole Creek area). There are now some indications that the persistent weak layer has gained strength in at least some areas. Data from around the rest of the forecast area over the past week indicating continued likely propagation along the persistent weak layer should not be set aside hastily. More observations are needed to get a full picture of the amount of ongoing instability on this weak layer on a regional scale.

Today's Primary Avalanche Concern: Persistent Deep Slabs

Despite snowpit data over the past two days indicating some strengthening of the persistent weak layer, concerns for instability remain ongoing on a regional scale. The possibility of isolated deep slab avalanches exists both above and below treeline on NW-N-NE aspects. This persistent weak layer of crusts and facets generally exists between five and eight feet deep in the snowpack. In the vast majority of areas this weak layer is buried too deep for a single skier or snowmobiler to transmit sufficient force through the snowpack to collapse and cause propagating failure of the snowpack along this layer. In isolated areas, this weak layer exists within 3 to 4 feet of the snow surface, well within the possibility of human triggering by a skier of snowmobiler. Any deep slab avalanches that occur at this time will be large and destructive. Spot probing for this low density snow layer is an effective way to determine the depth of the persistent weak layer in a given location.

Today's Secondary Avalanche Concern: Wet Snow Instability

As cloud cover decreases today, strong late March solar radiation and above freezing air temperatures will create minor amounts of wet surface snow instability. Most wet snow instability is expected to occur on E-SE-S-SW-W aspects. Areas that received 3 to 4 inches of new snow last night will see greater instability especially on wind loaded E-SE aspects. Wet loose snow avalanche activity rather than wet slab avalanche activity is expected. Most areas of wet snow instability today are expected to be rather small and shallow and not present a significant hazard to backcountry travelers. Secondary terrain hazards such as cliffs and terrain traps could magnify the consequences of becoming caught by an otherwise small and inconsequential avalanche.

The bottom line:

Very isolated 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 persistent deep slab instability. Large destructive human triggered deep slab avalanches remain possible in these areas. For all other areas, avalanche danger is generally LOW with isolated pockets of MODERATE danger due to warming instability near and above treeline on wind loaded E-SE aspects 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:	17 to 26 deg. F.
Max. temperature in the last 24 hours:	34 to 43 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	30 mph
Maximum wind gust in the last 24 hours:	63 mph
New snowfall in the last 24 hours:	1 to 4 inches
Total snow depth:	48 to 80 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Partly cloudy skies. Scattered snow showers in the morning.	Mostly cloudy skies.	Cloudy skies with a slight chance of snow.
Temperatures:	37 to 47 deg. F.	24 to 31 deg. F.	39 to 49 deg. F.
Wind direction:	SW	SW	S
Wind speed:	15 to 25 mph with gusts to 40 mph.	20 to 30 mph with gusts to 45 mph.	25 to 35 mph with gusts to 50 mph.
Expected snowfall:	0 to trace in.	O in.	0 to trace in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Partly cloudy skies. Scattered snow showers in the morning.	Mostly cloudy skies.	Cloudy skies with a slight chance of snow.
Temperatures:	34 to 40 deg. F.	22 to 29 deg. F.	33 to 41 deg. F.
Wind direction:	SW	S	S
Wind speed:	40 to 50 mph with gusts to 75 mph. Gusts decreasing to 65 mph in the afternoon.	40 to 45 mph with gusts to 70 mph, increasing to 55 to 60 mph with gusts to 85 mph after midnight.	55 to 60 mph with gusts to 90 mph, decreasing to 45 to 50 mph with gusts to 80 mph in the afternoon.
Expected snowfall:	0 to trace in.	O in.	0 to trace in.