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 Avalanche Advisory was published on March 31, 2007:


March 31, 2007 at 0:00 am

Forecast Discussion:


The bottom line: At all elevations the avalanche danger is LOW this morning. Today's predicted increase in cloud cover should still allow isolated pockets MODERATE of avalanche danger to develop on sun exposed SE-S-SW slopes steeper than 35 degrees as daytime warming occurs. If today turns out to be mostly sunny, expect the snow to soften much faster and for wet snow instabilities to be more widespread.

The high pressure ridge should continue to weaken a little more today due to the low pressure system in the Pacific Northwest. This low will bring more cloud cover to the area for the weekend. The winds have shifted to the west and should continue to increase through the rest of the weekend. Temperatures should continue to increase today. Some slight cooling is forecasted to occur as the low in the Pacific Northwest gains more influence over the weather for Sunday and Monday. By early next week the high pressure ridge is forecasted to regain strength and should promote warm, dry weather.

Overnight temperatures along the Crest and in the Mt. Rose area were slightly above freezing last night. The sky was mostly clear last night so the snow surface should have refrozen due to radiational cooling. Today's air temperatures should be about the same as yesterday's, but the increasing cloud cover forecasted for today should hold some of the rapid thawing of the snow surface in check. The new snow should quickly go through enough melt-freeze cycles to be assimilated into the springtime snowpack and become part of the corn cycle. Over time this process will lead to an increase in stability; however, until the storm snow completely changes over to melt-freeze snow expect to see wet snow instabilities forming due to warm air temperatures and exposure to solar radiation. The increased cloud cover forecasted for today should cause the snow surface to remain frozen longer and cause wet snow instabilities to be less widespread. Human triggered rollerballs, pinwheels, and loose wet snow slides are all still possible on aspects with slopes steeper than 35 degrees that receive lots of sun today. Human triggered slabs are also still possible in these areas today. The new snow that has been deposited in cross loaded SE-S aspects and windloaded SW-W aspects will be most prone to warming instability today. However, any areas that were protected from NE-E winds and receive large amounts of solar radiation will be suspect.

A breakable sun crust has formed on the snow surface in areas that are exposed to the sun up to 9000'. Once the crust softens, the riding conditions are still variable because the new storm snow still has not made a complete transformation to melt-freeze conditions. On the same slope there are areas that are soft, supportable, and corn-like right next to zones of sticky, wet mashed potatoes. There are still some areas of unconsolidated snow on the NW-N-NE aspects that were sheltered from the east winds and that have enough tree cover to prevent much solar radiation from reaching the surface. Remember to continually evaluate the conditions as they change over the course of the day and be willing to change plans accordingly.

The bottom line: At all elevations the avalanche danger is LOW this morning. Today's predicted increase in cloud cover should still allow isolated pockets MODERATE of avalanche danger to develop on sun exposed SE-S-SW slopes steeper than 35 degrees as daytime warming occurs. If today turns out to be mostly sunny, expect the snow to soften much faster and for wet snow instabilities to be more widespread.

The Heavenly Ski Patrol has been generous enough to include the Sierra Avalanche Center as one of the benefactors of their annual fundraising party this year. The party is next Friday, April 6th from 7pm to midnight and tickets are $10. A portion of the proceeds will go to SAC. For more information please click here. We also will be raffling off a BCA backpack, beacon, shovel, and probe on April 17th as a way to say thanks to everyone who has sent us a donation in the mail or via Pay Pal. To be entered in this drawing all you have to do is donate $10 or more to SAC. Thanks to all our sponsors, the ski days, and everyone who has donated this season we have met our operating budget for this season and have a start on next year's funding. For more details about our financial situation please click here.

Andy Anderson, Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
34 deg. F
Max. temperature at Sierra Crest past 24 hours:
48 deg. F
Average wind direction at Sierra Crest past 24 hours:
Westerly
Average wind speed at Sierra Crest past 24 hours:
20 mph
Maximum wind gust at Sierra Crest past 24 hours:
47 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
66 inches
Mountain Weather Forecast For Today:
Increasing clouds throughout the day .
Temperature forecast for 8,000 to 9,000 feet:
44 to 50 degrees F.
Ridgetop winds forecast for the Sierra Crest:
Westerly at 15 to 20 mph with gusts to 35 mph
Snowfall expected in the next 24 hours:
0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, partly cloudy skies with daytime highs 50 to 56 degrees F. West winds at 10 to 15 mph with gusts up to 25 mph. Tonight, mostly cloudy skies with overnight lows 30 to 36 degrees F. West winds at 10 to 15 mph with gusts up to 25 mph. Tomorrow, mostly cloudy with daytime highs 46 to 52 degrees F. West winds at 15 to 20 mph with gusts to 35 mph.

Above 8000 Feet:
Today, partly cloudy skies with daytime highs 44 to 50 degrees F. West winds at 15 to 20 mph with gusts up to 35 mph. Tonight, mostly cloudy skies with overnight lows around 32 degrees F. West winds at 15 to 20 mph with gusts up to 50 mph. Tomorrow, mostly cloudy with daytime highs 36 to 46 degrees F. West winds at 25 to 35 mph with gusts to 60 mph.


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:

  Saturday: Saturday Night: Sunday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.