THIS AVALANCHE FORECAST EXPIRED ON May 4, 2020 @ 6:48 am
Avalanche Forecast published on May 3, 2020 @ 6:48 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

A good overnight refreeze and cooler windy weather will mean firm snow surfaces this morning. As the day warms up and the refreeze melts, avalanches of loose wet snow may become possible on steep sunny slopes this afternoon. Cornice fall will also remain possible. This afternoon MODERATE avalanche danger will form at all elevations. This is the last avalanche forecast for the season.

2. Moderate

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

2. Moderate

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

2. Moderate

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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
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Near-freezing temperatures combined with mostly clear skies during the night should have formed a thick layer of firm refrozen snow at the surface. Cooler temperatures and continued strong wind today will extend the time that this overnight refreeze remains supportable. "Cooler" in May still means daytime highs in the 50's above 7000 ft and long hours of intense sunshine on all aspects, so the supportable snow is unlikely to last all day. By this afternoon the overnight refreeze could melt away on some slopes exposing deep wet snow and loose wet avalanches may become possible on steep slopes. 

Expect firm snow on all aspects this morning. Soft wet snow will form on E-SE-S aspects first and move to other aspects as the day warms up. Once the snow starts getting wet and deep, it is time to avoid avalanche terrain by recreating on lower angle terrain without steep slopes above.

Recent loose wet avalanche in Polaris Bowl.

Photo: A recent loose wet avalanche in Polaris Bowl (south of Carson Pass).

Avalanche Problem 2: Cornice
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Falling cornices still represent a potential problem. Large pieces could break off of these overhanging waves of snow as they melt. These blocks of snow could injure a person and may entrain more wet snow or trigger a loose wet avalanche when they impact the slopes below them.

Cornices often break farther back from their edges than expected or at unexpected times. Staying far away from the edges of cornices and not traveling underneath cornices can help avoid this problem.

Debris from a recent cornice fall on Red Lake Peak Debris from a recent (last 5 days) cornice fall on Mt. Judah.

Photos: Debris from recent cornice failures on Red Lake Peak (Carson Pass area) and Mt. Judah (Donner Summit area).

recent observations
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* Spring melt-freeze conditions exist on all aspects and at elevations across the forecast area. Melting has also resulted in mostly bare slopes or patchy snow coverage on many southerly facing slopes and on all aspects below 7400 ft. 

* Observations from Red Lake Peak (Carson Pass area) and Mt. Judah (Donner Summit) yesterday found firm snow on most aspects in the morning. In both areas, the E-SE-S aspects had softened by mid-morning. On Red Lake Peak the NE aspects remained firm through mid-day at least, but those more northerly aspects did start to soften on Donner Summit around 11 am. In both of these areas, sun cups and runnels have formed on the snow surface. 

* Observers reported several recent cornice falls in both areas. Observers could also see a recent loose wet avalanche in Polaris Bowl (south of Carson Pass) from Red Lake Peak.

* Numerous glide cracks exist where the snowpack overlies steep slabs of rock. No glide avalanches have been reported.

Weather and CURRENT CONDITIONS
weather summary

Yesterday afternoon's cloud cover dissipated between midnight and 2 am leaving mostly clear skies for the rest of the night. Overnight lows fell into the low 30's above 8000 ft. The strong SW winds also continued through the night. Today's weather looks similar to yesterday's with continued strong SW winds and slightly cooler temperatures. After today the forecast calls for a warming trend through the rest of the week. 

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 30 to 36 deg. F.
Max. temperature: 40 to 50 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 25 to 35 mph
Maximum ridgetop wind gust: 68 mph
New snowfall: 0 inches
Total snow depth: 25 to 58 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Sunny. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 0%. Clear. Snow levels 7500 feet decreasing to below 7000 feet after midnight. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 50 to 56 deg. F. 27 to 32 deg. F. 56 to 62 deg. F.
Mid Slope Winds: Light winds becoming southwest 15 to 20 mph with gusts to 45 mph in the afternoon. Southwest around 15 mph with gusts to 35 mph in the evening becoming light. Light winds.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. No accumulation. | SWE = none.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Sunny. Snow levels 7000 feet increasing to 8500 feet in the afternoon. Chance of precipitation is 0%. Clear. Snow levels 7500 feet decreasing to below 7000 feet after midnight. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 44 to 50 deg. F. 25 to 30 deg. F. 50 to 56 deg. F.
Ridge Top Winds: Southwest 15 to 25 mph with gusts to 45 mph. Southwest 15 to 25 mph with gusts to 45 mph in the evening becoming light. Light winds.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. No accumulation. | SWE = none.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast 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 forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258