THIS AVALANCHE FORECAST EXPIRED ON February 24, 2018 @ 6:52 am
Avalanche Forecast published on February 23, 2018 @ 6:52 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger exists today for all elevations. Wind slab, loose dry, and storm slab avalanche problems may be encountered. Any areas of unstable snow will exist within greater surrounding areas of seemingly stable snow. Signs of instability may not readily present themselves today unless you are actively assessing for them.

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: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

A wind slab avalanche problem created by snowfall and SW winds for most of the past 24 hours remains possible on NW-N-NE-E-SE aspects in near and above treeline terrain. Avalanche size up to D2 remains possible (large enough to bury or injure a person).

The shift to light NE winds last night is expected to have had minimal scouring and redistribution effects on recently formed wind slabs. A strong N wind event forecast for this evening will create new areas of blowing snow, potentially creating additional wind slabs on E-SE aspects. Little in the way of problematic wind slab formation is expected to occur on S-SW-W aspects due to very thin snow cover. The forecast wind shift back to SW after midnight tonight will return the focus back to NW-N-NE-E-SE aspects.

Identify and avoid areas of potentially unstable wind slab by looking for newly wind drifted snow. Slopes near or adjacent to a recent avalanche or those that have cornice features or wind pillows across the upper portion of the slope are the most suspect. Fragile cornices were reported yesterday and can collapse easily under the weight of a person. Areas of snow surface cracking in near treeline and above treeline terrain are an additional indication of unstable snow.

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

Small loose dry avalanches remain a possibility in steep wind protected areas below treeline where storm slabs did not form. This is most likely to occur in areas with significant previous snow cover, mainly NW-N-NE-E aspects.

Consider how terrain may increase the consequences of a small loose dry avalanche. Being pushed into a terrain trap or over a cliff could greatly change the outcome from what might otherwise be a small inconsequential avalanche.

Avalanche Problem 3: Storm Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Storm slabs are an unlikely avalanche problem today but may occur in isolated wind protected areas below treeline on NW-N-NE-E aspect terrain. Snowpack failure would occur either within the new snow or at the old/new snow interface in most locations. Snowpack failure could potentially occur a few inches below the old/new snow interface on faceted snow in the Carson Pass area or in other areas without recent field observations. Avalanche size is most likely D1 with the isolated possibility of an avalanche up to size D2 (large enough to bury or injure a person).

Avoid steep terrain in below treeline areas where any signs of instability have been observed. Human triggered snow surface cracking and/or recent avalanches are the easiest to identify signs of unstable snow.

recent observations
Submit Observations

* Signs of wind drifted snow and minor wind slab formation were observed yesterday on Incline Lake Peak (Mount Rose area) and along Frog Lake Ridge (Carson Pass area). Fragile cornices were noted in both areas.

* Some signs of isolated developing storm slabs were noted yesterday on Incline Lake Peak (Mount Rose area) and along Frog Lake Ridge (Carson Pass area). On Frog Lake Ridge, faceted snow a few inches below the old/new snow interface was identified as a potentially problematic weak layer.

* Very small human triggered loose dry avalanches were observed on Incline Lake Peak (Mount Rose area) and reported from near Grouse Rock (Ward Canyon area).

Weather and CURRENT CONDITIONS
weather summary

A break in the weather will occur today. Yesterday's storm system has moved out of the area. A few lingering isolated snow showers may occur today. The next weather system to affect the forecast area will pass by to the north on Saturday. Increasing cloud cover and strong winds will be the main effects of this system. A strong N wind event is forecast to occur over the upper elevations this evening followed by strong SW winds after midnight. Strong SW winds will continue into Saturday. A bit of a warm up is expected Saturday with maximum daytime air temperatures at the mid and upper elevations reaching the mid 20s to low 30s.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 1 to 8 deg. F.
Max. temperature: 12 to 20 deg. F.
Average ridgetop wind direction: SW shifting to NE
Average ridgetop wind speed: SW 33 mph | NE 19 mph
Maximum ridgetop wind gust: SW 75 mph | NE 29 mph
New snowfall: 6 to 12 inches
Total snow depth: 34 to 58 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy skies. Scattered snow showers. Clear skies. Partly cloudy skies, becoming mostly cloudy.
Temperatures: 21 to 26 deg. F. 10 to 16 deg. F. 28 to 33 deg. F.
Mid Slope Winds: NE Variable SW
Wind Speed: Generally light winds. Gusts to 35 mph in the afternoon. Light winds Light winds becoming 15 to 25 mph with gusts to 50 mph in the afternoon.
Expected snowfall: Up to 2 0 0
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy skies. Scattered snow showers. Clear skies. Partly cloudy skies, becoming mostly cloudy.
Temperatures: 16 to 22 deg. F. 8 to 13 deg. F. 23 to 29 deg. F.
Ridge Top Winds: NE N shifting to SW W
Wind Speed: 10 to 15 mph with gusts to 40 mph in the afternoon. 20 to 30 mph with gusts to 70 mph, shifting and decreasing to 15 to 25 mph with gusts to 55 mph after midnight. 15 to 25 mph increasing to 25 to 35 mph in the afternoon. Gusts up to 75 mph.
Expected snowfall: Up to 2 0 0
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