Eastern Sierra Snowpack Summary - 2016-02-08 05:56

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THIS ADVISORY EXPIRED ON February 10, 2016 @ 5:56 am
Avalanche Advisory published on February 8, 2016 @ 5:56 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

As high pressure continues through the week, with sunny skies and well above average temperatures, slopes that face E-SE-S-SW at all elevations will warm rapidly with crusts going from supportive to unsupportive depending on aspect, and time of day. Possible wet loose and wet slabs maybe encountered on steep (>35 degrees) slopes as they warm from the sun exposure.  Plan to be on and off of these types of slopes early before they warm too much.  Signs of rollerball (pin wheels) activity is an indicator of weakening bonds and rapid warming of the surface snow, which can lead to larger slope failures.  Natural and human triggered wet avalanches maybe possible, starting on southeast slopes in the morning and moving around the compass toward southwesterly by afternoon.  At elevations below 8500’, even non-solar aspects will warm, and risk of wet slide activity on these slopes (NE-N-NW-W) will increase on slopes >35 degrees in the afternoon. 

Avalanche Character 2: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Moderate winds at upper elevations should continue for the next few days.  Yesterday these winds were out of the NE, today they are forecasted to continue out of the East and Tuesday they should shift out of the SW.  Snow transport was visible yesterday over ridge-tops, likely forming new small sensitive windslabs in steep exposed terrain.  As wind direction shifts through the following days, these windslabs will form on a variety of leeward aspects.  Keep on the lookout for dense hollow sounding snow, and assess them with quick hand pits.  Remember, even small avalanches in the wrong spot can knock you off balance and lead to injury or worse in dangerous terrain.  

Snowpack Discussion

The avalanche concern through the next few days will be focused on wet snow instability on solar aspects at all elevations and isolated small windslabs in upper elevation steep exposed terrain on a variety of aspects. 

As high pressure continues through the week, with sunny skies and well above average temperatures, slopes that face E-SE-S-SW at all elevations will warm rapidly with crusts going from supportive to unsupportive depending on aspect, and time of day. Possible wet loose and wet slabs maybe encountered on steep (>35 degrees) slopes as they warm from the sun exposure.  Plan to be on and off of these types of slopes early before they warm too much.  Signs of rollerball (pin wheels) activity is an indicator of weakening bonds and rapid warming of the surface snow, which can lead to larger slope failures.  Natural and human triggered wet avalanches maybe possible, starting on southeast slopes in the morning and moving around the compass toward southwesterly by afternoon.  At elevations below 8500’, even non-solar aspects will warm, and risk of wet slide activity on these slopes (NE-N-NW-W) will increase on slopes >35 degrees in the afternoon. 

Non-solar aspects (NE-N-NW-W) at mid to upper elevations remain cool, and the snow is remaining wintery.  Moderate winds at upper elevations should continue for the next few days.  Yesterday these winds were out of the NE, today they are forecasted to continue out of the East and Tuesday they should shift out of the SW.  Snow transport was visible yesterday over ridge-tops, likely forming new small sensitive windslabs in steep exposed terrain.  As wind direction shifts through the following days, these windslabs will form on a variety of leeward aspects.  Keep on the lookout for dense hollow sounding snow, and assess them with quick hand pits.  Remember, even small avalanches in the wrong spot can knock you off balance and lead to injury or worse in dangerous terrain.  

recent observations

Plenty of loose wet slide activity has been witnessed off steep E-SE-S facing slopes throughout the region over the last few days.  Several steep south-facing gullies above Tioga Rd released Thursday or Friday during the first significant warming after last week’s storms.  These were large enough to bury a car.   

Stability tests over the last few days in areas with windslabs have been showing overall that windslabs have been continuing to stabilize.  However, some isolated locations where recent deposits have formed do show sensitivity.   

 

weather

High Pressure will continue through the week, providing plenty of sunshine and well above average temperatures.  Expect highs in the upper 40s to upper 50s above 10,000 for Monday and Tuesday, and slightly cooler on Wednesday.  Moderate winds at upper elevations will blow out of the East on Monday, and shift to the southwest on Tuesday.  At lower elevations, winds should be fairly calm.   

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Monday Monday Night Tuesday
Weather: SUNNY CLEAR SUNNY
Temperatures: UPPER 40S TO MID 50S deg. F. MID 20S TO MID 30S deg. F. UPPER 40S TO MID 50S deg. F.
Wind direction: SOUTHEAST SOUTHEAST SOUTH
Wind speed: 15 TO 20 MPH. GUSTS UP TO 30 MPH IN THE MORNING. 10 TO 15 MPH. GUSTS UP TO 25 MPH IN THE EVENING. 10 TO 15 MPH.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Monday Monday Night Tuesday
Weather: SUNNY CLEAR SUNNY
Temperatures: UPPER 40S TO MID 50S deg. F. MID 20S TO LOW 30S deg. F. MID 40S TO MID 50S deg. F.
Wind direction: EAST SOUTHEAST SOUTH
Wind speed: 20 TO 30 MPH WITH GUSTS TO 40 MPH. 15 TO 20 MPH WITH GUSTS TO 30 MPH. 15 TO 20 MPH WITH GUSTS TO 30 MPH.
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

This snowpack summary applies only to backcountry areas outside established ski area boundaries. This snowpack summary only describes general avalanche conditions and local variations always occur. This snowpack summary expires 24 hours after the posted time unless otherwise noted. 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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