Avalanche Advisory published on March 27, 2015 @ 6:48 am
This advisory is valid for 24 hours
Issued by Brandon Schwartz - Tahoe National Forest
bottom line

Avalanche danger is LOW for all elevations and aspects. Minor loose wet instabilities are expected during the afternoon hours. Loose wet avalanches large enough to bury or injure a person are unlikely. Normal caution is advised. Sufficient snow cover for avalanche activity on SE-S-SW-W aspects exists only in isolated portions of the forecast area. Much deeper, continuous snow cover exists on NW-N-NE-E aspects.

How to read the advisory


Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.

avalanche danger

How to read the advisory

1. Low

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Above Treeline

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Near Treeline

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Below Treeline

Avalanche danger is LOW for all elevations and aspects. Minor loose wet instabilities are expected during the afternoon hours. Loose wet avalanches large enough to bury or injure a person are unlikely. Normal caution is advised. Sufficient snow cover for avalanche activity on SE-S-SW-W aspects exists only in isolated portions of the forecast area. Much deeper, continuous snow cover exists on NW-N-NE-E aspects.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.
weather

Strong high pressure in place over the region will allow for record air temperatures today at the lower elevations. Increasing southwest ridgetop winds are expected to mix the atmosphere and actually lower maximum daytime air temperatures at the mid and upper elevations by a couple of degrees as compared to yesterday. Light winds last night have allowed for air temperature inversion conditions to set up this morning. Remote sensors are reporting air temperatures between 8,000' and 9,600' in the low to mid 40s this morning with air temperatures in the 30s for the majority of locations below 7,000'. Maximum daytime air temperatures are forecast to reach the low 50s to low 60s today for areas above 7,000'. Ridgetop winds shifted from east to southwest yesterday afternoon and have remained light in speed. Winds are forecast to increase to moderate speed this afternoon, becoming strong overnight. For Saturday expect some increase in cloud cover, slightly cooler maximum daytime air temperatures, and decreasing winds.

recent observations

Observations made yesterday on Tamarack Peak (Mount Rose area) revealed that recent storm snow on E aspects was rapidly assimilating with the older melt-freeze crust below it. All N-NE-E aspects traveled held ski and boot supportable melt-freeze crust under either dry or wet surface snow at mid day. True north aspects in this area between 9,000' and 10,000' held 2 to 4 inches of recent storm snow that had yet to undergo its first melt-freeze cycle as of mid day yesterday. Skier triggered roller balls and pinwheels up to 12 inches in diameter were widespread on E aspects at all elevations by 11 am. Numerous ski cuts on NE-E aspects produced only roller balls and pinwheels. No loose wet sluffs were observed prior to departure from the area at 12:30 pm.

A report was received for yesterday from an party that toured west of Carson Pass on a W aspect between 8,500' and 9,000'. Surface wet snow 1 to 2 inches deep over supportable melt-freeze crust was noted around 1 pm. Surface wet snow depth progressed to 3 to 5 inches later in the afternoon. Skier triggered roller balls up to 6 inches in diameter were noted, with no additional evidence of surface wet snow instability observed.

Avalanche Problem 1:   Loose Wet
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    unlikely
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    Same Danger

Minimum air temperatures were several degrees warmer last night at the mid and upper elevations than they have been the past two nights. Despite the warmer air temperatures, a decent overnight snow surface refreeze is expected to have occurred due to radiational cooling under clear skies. This refreeze could be a bit thinner than what existed the past two mornings. As daytime warming progresses, areas of surface wet snow will form again today on sun exposed slopes. Little to no snow cover remains on the vast majority of SE-S-SW-W aspects. Instability concerns on these aspects are confined to highly localized areas where continuous snow cover exists. E aspects continue to hold significant snow cover around the vast majority of the forecast area. Surface wet snow several inches deep will exist on E aspects by this afternoon. Sun angles are still not quite high enough to create large amounts of snow surface melt on NW-N-NE aspects 35 degrees and steeper. As a result, a lesser degree of surface wet snow formation will continue to occur on steep northerly aspects. With free water drainage well established on all aspects, wet snow instability is expected to be limited to human triggered roller balls, pinwheels, and human triggered loose wet sluffs in steep terrain that require a push to set into motion. Loose wet avalanches large enough to bury or injure a person remain unlikely today. Keep in mind that terrain traps such as gullies and cliffs below can greatly magnify the consequences of very small avalanches that would otherwise be too small to bury or injure a person.

CURRENT CONDITIONS  Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 40 to 46 deg. F.
Max. temperature in the last 24 hours: 57 to 58 deg. F.
Average wind direction during the last 24 hours: East shifting to southwest
Average wind speed during the last 24 hours: 14 mph
Maximum wind gust in the last 24 hours: 27 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 13 to 39 inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
  Friday Friday Night Saturday
Weather: Sunny skies. Clear skies, becoming partly cloudy. Partly cloudy skies.
Temperatures: 54 to 61 deg. F. 36 to 42 deg. F. 49 to 56 deg. F.
Wind direction: SW SW SW
Wind speed: Light winds increasing to 15 to 20 mph with gusts to 30 mph in the afternoon. 20 to 30 mph with gusts to 45 mph. 15 to 20 mph with gusts to 30 mph in the morning, becoming light.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
  Friday Friday Night Saturday
Weather: Sunny skies. Clear skies, becoming partly cloudy. Partly cloudy skies.
Temperatures: 52 to 58 deg. F. 34 to 40 deg. F. 48 to 54 deg. F.
Wind direction: SW SW SW
Wind speed: 10 to 15 mph, increasing to 20 to 25 mph with gusts to 40 mph in the afternoon. 35 to 45 mph. Gusts to 65 mph increasing to 75 mph after midnight. 25 to 30 mph with gusts to 45 mph in the morning, becoming light.
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.

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