THIS AVALANCHE ADVISORY EXPIRED ON April 23, 2017 @ 6:47 am
Avalanche Advisory published on April 22, 2017 @ 6:47 am
Issued by Brandon Schwartz - Tahoe National Forest

LOW avalanche danger early this morning will increase to MODERATE avalanche danger in response to daytime warming as the day progresses. Areas of loose wet avalanche problems are expected to develop on all aspects at all elevations today. Cornice collapse may continue to occur today, presenting an additional hazard to backcountry travelers.

2. Moderate

?

Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Despite above freezing air temperatures last night in most locations, a decent snow surface refreeze is expected to have occurred on open slopes due to radiational cooling under clear skies. Snow surface refreeze in treed areas may have been poor. Once last night's surface refreeze melts away in response to daytime warming, areas of loose wet avalanche problems will become possible. Instability is expected to eventually form on all aspects at all elevations today. Sun exposed areas that received wind loading during the last storm event as well as the more shaded northerly aspects hold the most transitional snowpack and could remain especially problematic today.

Monitor the thickness and supportability of melt-freeze crust at the snow surface. Avoid travel in or below avalanche terrain where this crust has melted away leaving unsupportable wet snow conditions.

Avalanche Problem 2: Cornice
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Large to very large cornices exist in many locations around the forecast area. These cornices are becoming weak and collapsing during the current warm spell. Cornices tend to break off much further back along the ridgetop than anticipated. Give cornice areas a wide berth during both ridgetop travel and if traveling on the slope below. During ridgetop travel, look for exposed rocks along the ridgetop that give indications of areas that are truly off of the cornice. A cornice collapse may or may not trigger an avalanche on the slope below. Either way, a person involved with falling high mass cornice pieces stands a good chance of significant crush injury or fatality.

advisory discussion

The last advisory of the season will occur tomorrow, April 23rd.  Click here for more information regarding the scheduled end date.

recent observations

Observations made yesterday on Rose Knob Peak (Mount Rose area) revealed areas of cornice collapse and signs of loose wet avalanche problems. Surface snow from the most recent storm event remains transitional, especially on northerly aspects. Natural and human triggered cornice collapse has been reported over the past two days. One human triggered incident on Thursday near Castle Peak (Donner Summit area) led to a broken leg.

Weather and CURRENT CONDITIONS
weather summary

Weak weather systems will pass by to the north of the forecast area today and tomorrow. Increasing SW winds and periods of cloud cover are expected as the main effects locally. Air temperature inversion conditions are in place this morning, despite the increasing SW winds. Many remote sensors in the 7,500' to 8,500' range are reporting air temperatures in the low to mid 40s this morning. Maximum daytime air temperatures are forecast to reach into the 50s today for most locations. Ridgetop winds are increasing this morning with moderate to strong SW winds expected for today, tonight, and tomorrow. Maximum daytime air temperatures are expected to cool 5 to 10 degrees for tomorrow vs. today.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 34 to 44 deg. F.
Max. temperature in the last 24 hours: 52 to 57 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 15 mph
Maximum wind gust in the last 24 hours: 45 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 124 to 190 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies, becoming partly cloudy. Mostly cloudy skies, becoming partly cloudy. Partly cloudy skies, becoming sunny.
Temperatures: 52 to 58 deg. F. 30 to 35 deg. F. 46 to 54 deg. F.
Wind Direction: SW SW SW
Wind Speed: Up to 10 mph in the morning, increasing to 10 to 20 mph with gusts to 40 mph in the afternoon. 15 to 20 mph. Gusts to 45 mph decreasing to 30 mph after midnight. 15 to 20 mph with gusts to 35 mph.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies, becoming partly cloudy. Mostly cloudy skies, becoming partly cloudy. Partly cloudy skies, becoming sunny.
Temperatures: 47 to 55 deg. F. 29 to 34 deg. F. 37 to 45 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 25 mph with gusts to 40 mph, increasing to 25 to 35 mph with gusts to 60 mph in the afternoon. 25 to 40 mph with gusts to 60 mph. 20 to 35 mph with gusts to 50 mph.
Expected snowfall: 0 in. 0 in. 0 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.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258