Avalanche Advisory: Sunday - Feb 25, 2018

THIS AVALANCHE ADVISORY EXPIRED ON February 26, 2018 @ 6:39 am
Avalanche Advisory published on February 25, 2018 @ 6:39 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Strong winds yesterday afternoon and evening shifted from the W to the NE and stripped more snow from slopes, and likely created new small wind deposits in some leeward terrain.  MODERATE avalanche danger exists at and above tree-line where isolated pockets of wind slab may remain sensitive to human triggering today.      

2. Moderate

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

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The 3-15” of very light snowfall that fell on Thursday has been blown back and forth and into the atmosphere in all but the most sheltered areas as moderate to strong winds have been shifting around the compass for the last several days.  The strongest winds have been out of the S and SW, which occurred during the snowfall event and then again yesterday afternoon.  Some significant wind slabs formed, such as the one on a NE slope below the ridgetop of Bloody Couloir which was triggered by skiers on Friday.  Little avalanche activity has been noted besides that, but it is likely that yesterday’s strong W and then NE winds built some new small windslabs.  Isolated areas could be sensitive to human triggering today, either from more recent deposits, or older more stubborn deposits.  All aspects are suspect, but the most likely places one might encounter a sensitive wind slab are above tree-line on NW-N-NE-E-SE facing slopes, just below ridgelines, on the edges of gullies and around other features that promote drifting.  Keep alert to denser deposits of snow, and do your own localized assessments. 

advisory discussion

Light NW winds this morning that will shift out of the W and increase slightly this afternoon will not likely lead to anymore wind slab deposition, as the previous days strong winds have not left much loose snow behind.  Today’s warmer temperatures and calmer winds could allow some S to SE facing slopes to warm slightly, and some very small loose wet activity could be possible, but should not be concerning.    

Weather and CURRENT CONDITIONS
weather summary

We’ll have a relative calm before the storm today, with sunny skies and breezy conditions (not nearly as windy as yesterday), and the warmest temperatures we’ve seen in over a week with highs reaching the low 30s around 10,000’. 

Winds will shift and pick up again tonight ahead of another cold front bringing light amounts snow for Monday into Tuesday morning.  This inside-slider should be similar to the last.  Then another dry day Wednesday before finally a good sierra storm for Thursday into Friday!  Confidence is growing that this should be the most significant storm of the season, with a good moisture tap from the Pacific, cold temps and low snowline, and several waves of heavy snowfall that likely be measured in feet!

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Sunny Partly cloudy Mostly cloudy. Snow likely.
Temperatures: 34 to 40 deg. F. 13 to 18 deg. F. 23 to 29 deg. F.
Wind Direction: West Southwest Southwest
Wind Speed: Light increasing to 10 to 15 mph in the afternoon. Gusts up to 30 mph. 20 to 30 mph with gusts to 65 mph. 15 to 25 mph. Gusts up to 65 mph decreasing to 40 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 80% chance 1 to 4 inches. 20% chance of 5 to 7 inches. in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Sunny Clear then becoming partly cloudy. Mostly cloudy. Snow likely.
Temperatures: 27 to 32 deg. F. 8 to 14 deg. F. 16 to 22 deg. F.
Wind Direction: Northwest shifting to the west in the afternoon. West shifting to the southwest after midnight. Southwest
Wind Speed: 20 to 30 mph decreasing to 15 to 20 mph in the afternoon. Gusts up to 40 mph. 0 to 35 mph with gusts to 60 mph increasing to 35 to 50 mph with gusts to 80 mph after midnight. 30 to 50 mph with gusts to 80 mph decreasing to 20 to 30 mph with gusts to 50 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 80% chance 1 to 5 inches. 20% chance of 8 to 8 inches. in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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