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.

High pressure is in place over the forecast area. Another day of sunny skies, light winds, and well above freezing air temperatures is expected for today. An air temperature inversion is in place over much of the forecast area this morning. The coldest air temperatures of low 20s to low 30s are reported from remote sensors below 7,000'. Much warmer air temperatures in the upper 30s to mid 40s are reported by remote sensors between 7,000' and 9,650'. Maximum daytime air temperatures in the 40s and 50s are forecast today for areas above 7,000'. Ridgetop winds shifted from east to southwest early this morning. Ridgetop winds are expected to remain out of the southwest for the next several days. Wind speeds are forecast to remain light to moderate through tomorrow.

Recent Observations:

Observations made yesterday on Silver Peak (Pole Creek area) and on Ralston Peak (Echo Summit area) continued to show ongoing instability on 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. On Silver Peak, the amount of faceting had increased since the last observations in this area on March 3rd. The persistent weak layer had become even softer and faceting had spread into the lower portion of the overlying slab (pit profile, video, more info). On Ralston Peak, similar evidence of continued faceting and likely propagation along the persistent weak layer were observed (videos, more info). Recent east winds had scoured snow off of only the very top portion of N-NE aspect avalanche start zones in both areas. 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. Recently formed wind slabs on S-SW aspects were stable and not reactive to the weight of a skier or in snowpit tests in either area.

Today's Primary Avalanche Concern: Persistent Deep Slabs

It is one of those days where it is difficult to trigger avalanches, but if an avalanche is triggered it is going to go big. The increased strength of the overlying slab has made it harder to transmit sufficient force down into the snowpack to collapse the persistent weak layer below. If a trigger point such as an exposed or shallow buried rock that brings the weak layer closer to the snow surface is loaded and the weak layer is collapsed, recent snowpack data indicates that this collapse is likely to propagate long distances through the snowpack. This would create a large deep slab avalanche in sufficiently steep terrain. Since triggering is currently more difficult, it is likely that several people could leave tracks on a slope before a trigger point is found that will initiate an avalanche. Keep in mind that this weak layer exists in the vast majority of areas both above and below treeline on NW-N-NE aspects. The weak layer is buried anywhere from 6 inches to 5 feet deep in the snowpack. The current penetration depth of skis and snowmobiles will not disrupt the weak layer, keeping even fully tracked out slopes suspect for future loading events such as the forecast storms next week.

Today's Secondary Avalanche Concern: Warming Instabilities

Well above freezing air temperatures and light winds will allow for wet surface snow to form quickly 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 only expected to pose a threat to backcountry travelers when combined with secondary terrain hazards such as cliffs and 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:	38 to 39 deg. F.
Max. temperature in the last 24 hours:	42 to 50 deg. F.
Average wind direction during the last 24 hours:	East
Average wind speed during the last 24 hours:	15 mph
Maximum wind gust in the last 24 hours:	35 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	31 to 49 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Sunny skies.	Clear skies.	Partly cloudy skies.
Temperatures:	49 to 56 deg. F.	25 to 35 deg. F.	45 to 52 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	Light winds	15 to 20 mph with gusts to 30 mph.	15 to 25 mph with gusts to 40 mph.
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Sunny skies.	Clear skies.	Partly cloudy skies.
Temperatures:	42 to 50 deg. F.	25 to 35 deg. F.	38 to 45 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	Light winds increasing to 10 to 15 mph with gusts to 25 mph in the afternoon.	15 to 25 mph with gusts to 40 mph.	20 to 30 mph with gusts to 45 mph.
Expected snowfall:	O in.	O in.	O in.