Avalanche Advisory published on April 21, 2014 @ 6:34: Issued by Brandon Schwartz - Tahoe National Forest
bottom line

We have stopped issuing daily avalanche advisories for the 2013-2014 season as our funding allotted for this season is now exhausted. Avalanche advisories will resume in the fall of 2014.

Avalanche activity can and most likely will continue to occur this spring as additional storm cycles impact the forecast area. Continue to monitor changing conditions and use caution when traveling in the backcountry. For general spring avalanche information please read the full spring avalanche statement.

How to read the advisory


avalanche danger

How to read the advisory

No Rating

?

Above Treeline

No Rating

?

Near Treeline

No Rating

?

Below Treeline

We have stopped issuing daily avalanche advisories for the 2013-2014 season as our funding allotted for this season is now exhausted. Avalanche advisories will resume in the fall of 2014.

Avalanche activity can and most likely will continue to occur this spring as additional storm cycles impact the forecast area. Continue to monitor changing conditions and use caution when traveling in the backcountry. For general spring avalanche information please read the full spring avalanche statement.


Avalanche Problem 1:   Loose Wet
type aspect/elevation ? characteristics
likelihood ? size ? trend ?
likely
unlikely
large
small

Loose wet avalanche activity will continue to occur this spring. Usually this type of instability forms in response to daytime warming. With many previous melt-freeze cycles and rain events having already occurred this past winter and spring, free water drainage from the snowpack is well established. This is expected to keep the majority of wet snow avalanche activity limited to human triggered loose wet avalanches.

You can use the Snotel and National Weather Service sites to monitor hourly temperatures at many points throughout the forecast area. Cloudy skies overnight and air temperatures above freezing do not allow the snowpack to refreeze very well. When the snowpack does not refreeze overnight, other springtime activities that do not involve snow travel on steep slopes represent more prudent choices. Under clear skies, the top few inches of the snowpack will often refreeze despite near or slightly above freezing air temperatures. This superficial refreeze usually allows for a short period of good travel conditions during the early morning hours before surface wet snow instability becomes a concern. If a solid overnight refreeze occurs, getting out early and finishing in time to have a mid day barbecue should be your goal. Start with east aspects and follow the sun to south, then to west, and finally to north aspects. Get off of your equipment on a regular basis and check boot penetration depth. Boot-top deep wet snow, significant roller ball activity, or any loose wet avalanche results from small test slopes all indicate that wet snow instabilities can occur. Moving to a different aspect with less sun exposure, terrain less than 25 degrees in slope angle without steeper terrain above, or simply heading over to the beach for a picnic all represent good choices for avalanche avoidance at that point. As a matter of etiquette, do not leave deep ruts in a slope that will freeze overnight and ruin the slope for others the next day.

Avalanche Problem 2:   Wind Slab
type aspect/elevation ? characteristics
likelihood ? size ? trend ?
likely
unlikely
large
small

Natural and human triggered wind slab avalanches may occur during and immediately after any late season storms. Expect a period of snowpack instability during the storm itself, then a second cycle of avalanche activity as rapid warming occurs post storm. During the storm, watch for typical signs of mid winter instability such as recent avalanche activity, wind loading, collapse, audible whumpfing sounds, and/or shooting cracks. Post storm, new snow will be very sensitive to rapid warming and direct sunlight. Pay close attention to layer bonding within the new snow and to the old snow surface beneath it. It can lose strength rapidly as the day progresses causing a significant increase in avalanche danger.

Avalanche Problem 3:   Wet Slab
type aspect/elevation ? characteristics
likelihood ? size ? trend ?
likely
unlikely
large
small

During periods of rapid warming after new late season snowfall, storm slabs and wind slabs can transition to wet slabs. The high angle sun in late April and May allows for significantly more incoming solar radiation to affect the snowpack on NW-N-NE-E-SE aspects than what occurs during December, January, and February. If an active weak layer exists at the base of a recently formed storm slab or wind slab, rapid warming of the snow surface can increase the deformation rate of the slab adding additional stress to the weak layer below. This can cause an increase in snowpack instability and in some cases cause natural avalanches to occur during periods of rapid warming post storm event under sunny skies.

advisory discussion

Other hazards such as cornice collapse, moats, glide cracks, and open creeks exist. Stay well back from abrupt edges along ridgelines as human triggered cornice collapse will remain possible during the spring. Stay out from under cornice areas that are not well frozen, especially if you can see water dripping from the cornice. Areas of weak snow around rocks, vegetation, and along the base of cliff bands exist. Move carefully around these features as the thin bridges of snow could collapse under body weight allowing you to fall into a melted hole next to the feature. Exercise caution when traveling near or attempting to cross creeks as wet snow along the banks can collapse under the weight of a person.

As the season begins to change, the morning air becomes crisp and the days become shorter, check back on our home page for early season fundraising events for the 2014-2015 season. Enjoy your spring and summer and we will see you again right here in the fall.

CURRENT CONDITIONS  Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: Check the SNOTEL and NWS remote sensor sites mentioned above. 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: inches
Total snow depth: inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
  Monday Monday Night Tuesday
Weather: Check in with the Reno NWS at the link above for the latest weather forecasts.
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: in. in. in.
For 8000 ft. to 9000 ft.
  Monday Monday Night Tuesday
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: in. in. in.
Disclaimer
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.


Subscribe to Central Sierra Avalanche Advisory | Avalanche Forecast From the Sierra Avalanche Center