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BACKCOUNTRY AVALANCHE FORECAST

OLYMPICS

ISSUED
Saturday, January 18, 2020 - 7:24AM Sat, Jan 18, 2020 - 7:24AM
AUTHOR
Dennis D'Amico
THE BOTTOM LINE

715 Update: The avalanche danger has been lowered to Considerable due to lower snow totals overnight.  

Dangerous avalanche conditions will develop overnight and linger through Saturday as a storm brings new snow, wind and rising snow levels to the Olympics. You are most likely to trigger an avalanche on steep open wind loaded slopes where firmer wind slabs have formed over recent colder weaker snow. Watch out for loose wet avalanches at lower elevations in the afternoon as snow levels rise. 

AVALANCHE DANGERi

Saturday, January 18, 2020
Above Treeline Considerable (3)
Near Treeline Considerable (3)
Below Treeline Considerable (3)

OUTLOOKi

Sunday, January 19, 2020
Considerable (3)
Considerable (3)
Moderate (2)

OUTLOOKi

Sunday, January 19, 2020
3 3 2
Danger Scalei
  • Low (1)
  • Moderate (2)
  • Considerable (3)
  • High (4)
  • Extreme (5)

AVALANCHE PROBLEM #1i

  • Storm Slab

    Avalanche Problemi
  • Above Treeline
    Near Treeline
    Below Treeline
    Aspect/Elevationi
  • Unlikely
    Possible
    Likely
    Very Likely
    Almost Certain
    Likelihoodi
  • Small (D1)
    Large (D2)
    Very Large (D3)
    Historic (D4-5)
    Sizei

After a cold and snowy week that nearly doubled the snowpack in the Olympics and filled in the below treeline snowpack with snow down to sea level conditions will begin to change Friday night and through the weekend as milder Pacific air moves into the region. 

Widespread small natural and human triggered avalanches are possible on steep slopes on all aspects and elevations, failing within the new storm snow or at the old snow interface. Wind loaded slopes will develop deeper slabs capable of producing larger avalanches. Avoid open slopes steeper than 35 degrees where you find firmer wind drifted snow; this is the most likely place to trigger an avalanche Saturday. Fresh cornices will likely be sensitive Saturday. Give cornices a wide berth as they often break further back than expected when traveling along ridgelines. Avoid traveling on slopes directly below cornices.   

Although not listed, wet loose avalanches will become increasingly likely below 3500'-4000' by the end of the day and may entrain significant new and recent snowfall. If the surface snow becomes wet, you see natural pinwheels or natural wet avalanches, it's time to avoid nearby steep slopes. 

 

January 16th, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

In the past week and a half, there have been five avalanche fatalities in three separate accidents in the US. One occurred near Kellog, ID and another outside of Baker City, OR. Local avalanche centers will perform accident investigations including final reports. You can find preliminary accident information at avalanche.org.

From January 9th to 16th the Pacific Northwest slid into deep winter. A cold and snowy regime brought a nearly continuous barrage of storms through the area. Temperatures bottomed out as modified arctic air made its way south from interior Canada, and many stations recorded the lowest temperatures of the season so far. A snowpack has been growing at lower elevations due to some lowland snow on both sides of the Cascades.  NWAC’s snow depth climatology report shows most stations have surpassed average depths on the ground for this time of year. Quite the comeback from two weeks ago, when most were at 25-64% of normal. 

Location

Total Snow Depth (in) 1/8/20

Total Snow Depth (in) 1/16/20

Hurricane Ridge

51

91

Heather Meadows Mt Baker

95

126

Stevens Pass

63

85

Snoqualmie Pass

33

77

Mission Ridge Mid Mtn

18

28

Crystal Mt Green Valley

66

92

Paradise Mt Rainier

105

138

White Pass Upper

69

110

Timberline

57

118

Mt Hood Meadows

53

98

Snow depths continued to rise. Total snow depths doubled in some locations.

The mountains went through a period of prolonged dangerous to very dangerous conditions as the snow kept coming. Many locations picked up over a foot of new snow per day for a number of days in a row, and storm slab instability was widely experienced across the region. At times, instabilities within new snow layers were very reactive, and you didn’t have to do much to provoke an avalanche. Many people triggered small to large soft slab avalanches, even well below treeline. The cold temperatures tended to preserve these instabilities longer than usual during this time. 

Small ski triggered storm slab near Mt Hood Meadows. January 11, 2020. Scott Norton photo.

This cold, low density snow was also susceptible to wind drifting as westerly winds buffeted the alpine zone from the 8th to the 15th. On the 15th the mean winds shifted, and a south and east wind event disturbed the powder on open, exposed terrain near the passes and at upper elevations throughout the region. This created wind slab problems in some unusual locations.

Wind slabs formed over the low density powder snow. Mt Baker Backcountry. January 15, 2020. Zack McGill photo.

Trailbreaking in undisturbed snow was often very deep and difficult. In most places at any point in the week you could step off your skis or machine and sink in up to your chest in deep powder snow. The deep snow presented hazards of its own such as tree wells, and made it very easy to get stuck on a machine or lose a ski. Many folks experienced excellent, deep powder conditions and stuck to conservative terrain choices. 

-MP

A cold winter’s day over the Chiwaukum Range, from Stevens Pass. Matt Primomo photo.

No Corresponding Mountain Weather Forecast Available