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.

This advisory was posted on Wednesday, February 21st, 2007 at 5:30 am

The bottom line: Avalanche danger is LOW for all elevations and aspects.

As the storm begins to move into the forecast area today, expect to see an increase in cloud cover, an increase in wind intensity, and slightly cooler temperatures than yesterday. The front edge of this storm should reach the central Sierras by this evening bringing colder temps and a few inches of snow overnight. The bulk of the moisture associated with this storm should move into the area tomorrow. During the day tomorrow there should be heavy snowfall and accumulations approaching 18 inches along the crest. The strong winds should continue to be out of the southwest throughout the storm. They may begin to diminish on Thursday afternoon. Since there is a much colder airmass associated with this storm, the snow should be nice and light. It will also be very easy for signifigant wind transport, wind loading, and subsequent wind slab formation to occur throughout the storm.

Yesterday snow surface conditions throughout the forecast area still consisted of melt-freezecrusts on all aspects below 8,500'. The exceptions are the Carson Pass and Luther Pass areas, where unconsolidated snow surface conditions remain after Sunday's snowfall. Above 8,500, a mix of melt-freeze crust, rough wind scoured and smooth wind scoured snow surfaces exist. Some of the more sheltered areas still had 1 to 2 inches of unconsolidated snow on top of these harder surfaces. A thin layer of graupel exists in this surface snow in some areas and in other areas the graupel simply rests on top of the crusts and wind scoured surfaces. In still other areas surface hoar crystals began to develop on Tuesday and continued to grow Wednesday night and last night. This variation in snow surface conditions may sound complicated and confusing, but the general message is that the snow surface is a mix of weak snow grains and hard, slippery surfaces. These surface conditions combined with a cold storm do not bode well for allowing any new snow the falls to bond well to the old snow surfaces. Another concern is that the winds associated with this storm will easily transport the light snow that is expected to fall during the storm. By tomorrow afternoon thick windslabs should have formed on many of the leeward slopes.

Overall the snowpack throughout the forecast area is currently in good condition to handle new snow loading. Layer bonding testsperformed over the past few days continue to show a strengthening trend in the snowpack structure. Future instability concerns at this time are mainly focused on the poor bonding expected to occur between the new snow and the existing snow surfaces and failures within the storm snow.

No avalanche activity was reported yesterday.For a list of avalanche activity reported to the Sierra Avalanche Center this season, click here.

The bottom line: Avalanche danger is LOW for all elevations and aspects.

At this time, we are still short $8,000 in funding for our operating budget this winter. If you use this service with any regularity and would like to continue to do so, please show your financial support for the Sierra Avalanche Center. You may make a tax deductible donation directly to us via Paypal or by sending a check to our address listed above, c/o the Truckee Ranger Station. A financial graph showing the amount of fundraising completed this season and our overall budget is available by clicking here. The financial support already received this winter from a variety of users is greatly appreciated.

Andy Anderson, Avalanche Forecaster
Today's Central Sierra Weather Observations:
0400 temperature at Sierra Crest (8,700 feet):
21 deg. F
Max. temperature at Sierra Crest past 24 hours:
34 deg. F
Average wind direction at Sierra Crest past 24 hours:
southwest
Average wind speed at Sierra Crest past 24 hours:
45-50 mph
Maximum wind gust at Sierra Crest past 24 hours:
70 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
51 inches
Mountain Weather Forecast For Today:
Partly cloudy this morning with cloud cover increasing throughout the day. There is a slight chance of snow in the afternoon
Temperature forecast for 8,000 to 9,000 feet:
26-31 deg. F
Ridgetop winds forecast for the Sierra Crest:
Southwest 45 - 55 mph with gusts over 70 mph
Snowfall expected in the next 24 hours:
3-6 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet
Today partly cloudy this morning with cloud cover increasing by this afternoon. There is a slight chance of snow in the afternoon. Winds should be out of the southwest at 25-35 mph gusting to 60 mph. Daytime highs 31 to 38 degrees F. Tonight, snow with up to 2 inches of accumulation in the northern part of the forecast area and less in the south. Southwest winds 25 to 35 mph with gusts to 60 mph. Overnight lows 23 to 28 degrees F. Thursday, snow with up to 14 inches of accumulation. Winds should continue to be out of the southwest at 30 to 35 mph with gusts to 60 mph. Daytime highs in the 20's.

Above 8000 Feet
Today partly cloudy this morning with cloud cover increasing by this afternoon. There is a slight chance of snow in the afternoon. Winds should be out of the southwest at 45-55 mph gusting to over 70 mph. Daytime highs 26 to 31 degrees F. Tonight, snow with up to 4 inches of accumulation in the northern part of the forecast area and less in the south. Southwest winds 45 to 55 mph with gusts to over 70 mph. Overnight lows 20 to 25 degrees F. Thursday, snow with up to 18 inches of accumulation. Winds out of the southwest 35 to 45 mph with gusts to 60 mph. Daytime highs should reach into the 20's in the morning and fall into the teens by the afternoon.

Backcountry Travelers:
We want to hear from you! If you see avalanche activity, or want to share condition information for an area you've been in, please let us know. Call (530) 587-3558 or e-mail us at:

sac_avalanche@fs.fed.us

.

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The bottom line:

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	deg. F.
Max. temperature in the last 24 hours:	deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours:	mph
Maximum wind gust in the last 24 hours:	mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.