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 high-pressure ridge should begin to build over the forecast area today as the low-pressure system moves south and east of the area. A slight chance for afternoon snow showers exists today as this transition occurs. A few clouds and light westerly winds should also accompany this change in weather. However, most of the forecast area should see lots of sunshine today. Daytime high temperatures should jump into the upper 30's to mid 40's at all elevations above 7000' today.

After adding one more inch of new snow yesterday morning, the storm total since April 8th has climbed to 10-20 inches. Areas south of Highway 50 received the most snow. The Carson Range east of Lake Tahoe received the least. Observations in the Mt. Rose backcountry yesterday showed 4-10 inches of snow sitting on top of the old melt/freeze crust. On the Sierra Crest near Barker Pass, 12-18 inches of snow existed on top of this crust. The new snow has bonded well to crust in both areas. Observations also showed rapid consolidation and strengthening within the layers of the new snow. In the Barker Pass area only a 1-2 inch section of the old melt/freeze snow had refrozen. Below this crust wet, unconsolidated snow still existed. One whumph occurred on a NE facing slope at about 7500' near Barker Pass where the frozen melt/freeze crust was thin. Skier triggered sluffs involving the top few inches of new snow occurred both in the Mt. Rose area and near Barker Pass yesterday on 38-40 degree N-NE-E facing slopes. Some small, naturally occurring roller balls and point-release slides occurred in both of these areas in the afternoon as the sun began to hit the snow surface.

Today, intense April sun on new snow and daytime highs 5-10 degrees warmer than yesterday will combine to make instabilities due to daytime warming the main avalanche concern. This rapid warming of the new snow will melt some of the bonds that have formed within the new snow layers and will weaken the snow. Enough warming could occur today for the free water that forms in the new snow to saturate the new snow layers since this snow has not had time for drainage channels to form in it. This free water and the melting bonds could cause the new snow to lose enough strength that human triggering of slab avalanches involving the snow above the old melt/freeze crust could occur. The most likely places for this type of avalanche activity are steep, sun-exposed E-SE-S-SW-W aspects. Naturally occurring wet-slab avalanches should remain unlikely due to some expected cloud cover this afternoon; however, they are not impossible especially on the most sun-exposed, cross-loaded SE aspects. Naturally occurring roller balls, pinwheels, and point release slides should also occur today.

 

The bottom line:

This morning the avalanche danger is LOW. Areas of MODERATE avalanche danger should quickly develop due to daytime warming on E-SE-S-SW-W aspects 37 degrees and steeper at all elevations today.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	22 deg. F.
Max. temperature in the last 24 hours:	33 deg. F.
Average wind direction during the last 24 hours:	Southwest shifting to the northeast after 11 pm last night
Average wind speed during the last 24 hours:	25 mph then decreasing to 5-10 mph
Maximum wind gust in the last 24 hours:	42 mph
New snowfall in the last 24 hours:	1 inches
Total snow depth:	142 inches

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

For 7000-8000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Partly cloudy with a slight chance of some afternoon showers	Partly cloudy	Partly cloudy
Temperatures:	42-48 deg. F.	24-30 deg. F.	44-51 deg. F.
Wind direction:	Northwest shifting to the west	West	Northwest shifting to the west
Wind speed:	10 mph	10-15 mph	10 mph
Expected snowfall:	trace in.	O in.	O in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Partly cloudy with a slight chance of some afternoon showers	Partly cloudy	Partly cloudy
Temperatures:	32-40 deg. F.	19-26 deg. F.	41-47 deg. F.
Wind direction:	Northwest shifting to the west	West shifting to the northeast	West
Wind speed:	10-15 mph with gusts to 25 mph increasing to 15-25 mph with gusts to 35 mph in the afternoon	15-20 mph with gusts to 35 mph decreasing to 10-15 mph with gusts to 25 mph after midnight	10-15 mph with gusts to 25 mph
Expected snowfall:	trace in.	O in.	O in.