Avalanche Advisory: Saturday - Jan 5, 2019

This Avalanche Advisory is brought to you by

 

 

 
 
 
 
 
-- placeholder --
 
 
 

THIS AVALANCHE ADVISORY EXPIRED ON January 6, 2019 @ 6:50 am
Avalanche Advisory published on January 5, 2019 @ 6:50 am
Issued by Steve Mace - ESAC

Human triggered avalanches will be likely today on exposed leeward slopes at mid and upper elevations. New snow and strong southwestern winds will create sensitive wind slabs on NW-N-NE-E-SE aspects where terrain features encourage drifting such as rollovers, gullies and leeward sides of ridgelines.  

As new snow accumulates this afternoon and into the evening be on the look out for developing storm slabs in sheltered areas on all aspects.

Early season obstacles still exist and the new snow will only make them harder to see, be cautious of a thin snow pack.

3. Considerable

?

Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

?

Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

?

Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Our first snowfall of the New Year will be accompanied by strong southwestern winds.  Expect to find sensitive wind slabs on NW-N-NE-E-SE aspects near and above tree line.  You can use visual clues to identify and avoid wind loaded slopes over 30 degrees. Recent cornice growth, blowing snow, snowdrifts, and uneven snow surfaces are all signs that wind slabs are in nearby terrain. With sustained strong winds and gusts expected to reach 90 mph today be on the look out for wind loading further down slopes, and in more protected areas you may not normally expect. The size and likelihood of human triggered wind slabs will increase throughout the day and into the evening as the snow continues to fall. Do your own localized assessments to determine how sensitive wind slabs are before committing to steeper, more complex terrain where consequences of a slide may be higher.  When in doubt, stick to more simple, sheltered terrain. 

Avalanche Problem 2: Storm Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

While risk of storm slabs this morning is very low, as snow accumulates this afternoon and particularly this evening it will possible to find storm slabs that are sensitive to human trigger developing on all aspects in sheltered areas at low and mid elevations. As the snowfall rate increases this afternoon be wary of steep terrain, convex rollovers, and unsupported slopes where the risk of triggering storm slabs is higher.  

advisory discussion

While the Avalanche danger will be low this morning, we expect it to rise throughout the day as new snow accumulates.  The biggest concern today will be Fresh wind slab development near and above tree line on NW-N-NE-E-SE aspects. These sensitive wind slabs will grow in size and likelihood through the afternoon and evening as the snow totals increase and the strong winds continue. Use small, benign slopes to investigate how newly loaded snow is reacting.   

As the new snow adds up this afternoon and into the evening it will be possible to see storm slab development on all aspects in sheltered areas at low and mid elevations.  As this problem gains traction it will be important to keep in mind the poor structure of our thin snow pack.  Faceting throughout the snow pack has created a weak base for the new snow to settle on.  Furthermore, recent observations of widespread surface hoar and near surface faceting are worth keeping in mind as there is a strong likelihood that new snow will not bond well with the old snow surface. While the strong winds preceding the incoming storm are likely to breakdown surface hoar in wind prone areas it may be possible to find some left standing in more sheltered areas.  Special variability will be important to consider as we move into this next storm cycle. After a long period of relatively benign, stable conditions it will be increasingly important to be vigilant as we enter into a time of increased danger and uncertainty. Now is a time to rein it in, practice good travel habits, and carefully evaluate conditions before committing to suspect terrain.

Weather and CURRENT CONDITIONS
weather summary

Winter weather will return to the area as the first in a series of storms arrives today.  Snow showers are expected to start in earnest this afternoon and continue into the evening hours. 1-3” of snow is expected today and 8-12” expected tonight.  Temperatures are expected to be below freezing today with a high of 26°f expected at upper elevations. Strong southwestern winds will continue throughout the day today with gusts expected to reach 90mph above 10,000ft.

We expect to see less snow on Sunday (3-6”) as temperatures drop with highs in the low 20’s.   Winds will continue to be strong out of the southwest. Expect gusts up to 75mph at upper elevations.  

Weather models are mixed as we move into next week.  A warming trend is expected with intermittent showers possible on Monday and Tuesday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming cloudy. Snow in the afternoon. Chance of precipitation is 70%. Cloudy. Snow. Chance of precipitation is 85%. Mostly Cloudy. Snow Likely
Temperatures: 25 to 33. deg. F. 16 to 21. deg. F. 22 to 28. deg. F.
Mid Slope Winds: South 15 to 30 mph with gusts to 75 mph. Southwest 15 to 25 mph with gusts to 55 mph. Southwest 15 to 25 mph. Gusts up to 40 mph increasing to 65 mph in the afternoon.
Expected snowfall: 1-3 in. 6-10 in. 2- 4 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy then becoming cloudy. Snow in the afternoon. Chance of precipitation is 85%. Cloudy. Snow. Chance of precipitation is 90%. Mostly cloudy. Snow likely.
Temperatures: 18 to 26. deg. F. 9 to 14. deg. F. 15 to 21. deg. F.
Ridge Top Winds: South 35 to 50 mph with gusts to 90 mph. Southwest 30 to 45 mph with gusts to 70 mph. Southwest 20 to 30 mph with gusts to 50 mph increasing to 30 to 45 mph with gusts to 75 mph in the afternoon.
Expected snowfall: 1-3 in. 8-12 in. 3-6 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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

ESAC receives support from ...