The last forecast for the 2022-2023 season was posted on April 30th. Thanks to everyone who supported the Sierra Avalanche Center this season by submitting observations, assisting with education, volunteering, and/or donating.

The last forecast for the 2022-2023 season was posted on April 30th. Thanks to everyone who supported the Sierra Avalanche Center this season by submitting observations, assisting with education, volunteering, and/or donating.
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April 3, 2011 at 6:20 am |
Early this morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will form in response to daytime warming on E-SE-S-SW-W aspects on slopes 37 degrees and steeper. |
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The weather system that brought cloud cover and anywhere from a trace to 0.4 inches of rain at 8,500' and 0 to 2 inches of new snow at the highest elevations of the forecast area yesterday has moved on. Clear skies and below freezing air temperatures at all elevations have moved in along with high pressure. Ridgetop winds remain out of the west this morning, but have decreased from strong to moderate in speed. Winds are forecast to shift from west northwest to northeast by this afternoon and generally decrease to light in speed. Maximum daytime air temperatures above 7,000' for today are expected in the upper 20s to low 40s, significantly colder than the last several days.
Observations made yesterday on Donner Pass (Donner Summit area) revealed no evidence of an overnight refreeze in that area. At 8:30am the top 1.5 to 2 feet of the snowpack was wet snow with free water visible in all wet snow layers at 7,140' on an open SE aspect. Free water production did appear to have decreased during the overnight hours, but without refreeze. At that time, the snow surface was increasing in melt rate and free water production (pit profile, more info). Similar conditions were noted during the mid morning hours on W-NW-N-NE-E aspects on Donner Peak up to the traveled highpoint of 7,600'.
Overnight, remote sensors reported air temperatures falling into the 20s at all locations across the forecast area. For most areas, below freezing air temperatures existed for the 7 to 12 hours leading up to 7am this morning. This is expected to have brought a solid overnight refreeze to the upper portion of the snowpack.
Primary Avalanche Concern: Warming Instability
As air temperatures climb above freezing today and the April amounts of solar radiation warm the snowpack, some areas of warming instability will form today. The greatest areas of instability are expected below 8,000' on slopes with direct sun exposure. With a solid overnight refreeze likely in place and fairly mild air temperatures for today, the entire freeze layer formed last night is not expected to melt today in the vast majority of areas. Wet surface snow on top of a supportable ice layer is expected to last nearly all day today. Human triggered wet loose snow avalanches are the expected form of instability today in steep terrain. Wet slab avalanches are unlikely.
Early this morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will form in response to daytime warming on E-SE-S-SW-W aspects on slopes 37 degrees and steeper.
0600 temperature: | 21 to 28 deg. F. |
Max. temperature in the last 24 hours: | 38 to 42 deg. F. |
Average wind direction during the last 24 hours: | West |
Average wind speed during the last 24 hours: | 49 mph |
Maximum wind gust in the last 24 hours: | 93 mph |
New snowfall in the last 24 hours: | 0 to 2 inches |
Total snow depth: | 108 to 175 inches |
For 7000-8000 ft: |
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Sunday: | Sunday Night: | Monday: | |
Weather: | Mostly sunny skies. | Clear skies. | Partly cloudy skies. |
Temperatures: | 35 to 43 deg. F. | 25 to 32 deg. F. | 49 to 56 deg. F. |
Wind direction: | W shifting to NE | NE shifting to SE | W |
Wind speed: | 5 to 10 mph. | Around 10 mph. | Up to 10 mph. |
Expected snowfall: | O in. | O in. | O in. |
For 8000-9000 ft: |
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Sunday: | Sunday Night: | Monday: | |
Weather: | Mostly sunny skies. | Clear skies. | Partly cloudy skies. |
Temperatures: | 26 to 32 deg. F. | 25 to 32 deg. F. | 41 to 49 deg. F. |
Wind direction: | W shifting to NE | E | NE shifting to W |
Wind speed: | 15 to 25 mph with gusts to 40 mph. Winds shifting and decreasing to 15 to 20 mph in the afternoon. | 10 to 20 mph with gusts to 35 mph. | 10 to 15 mph. |
Expected snowfall: | O in. | O in. | O in. |
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