Avalanche Advisory

Issued: Thursday, March 16, 2017 7:00 AM
Updated: Thursday, March 16, 2017 7:08 AM
Forecaster: Michael Hatch

Primary Problem

Secondary Problem


BOTTOM LINE:

We have two very distinct snowpack problems going on right now and its all dependent on elevation. Mountain locations below 8500ft have been getting significant precipitation the last several days largely in the form of rain. Rain on snow creates rapid instability in the snowpack. Natural and human-triggered wet loose and wet slab avalanches will remain a possibility through Saturday evening. In the alpine at elevations above 8500ft precipitation has come largely in the form of snow with 4-6" or more of new snow reported in the last 48 hours and another 6-8" forecast for Friday night. Combined with strong SW winds this has created sensitive pockets of wind slab 8-12" deep or more on leeward terrain features at ridgeline and mid-slope. Cornice fall is also a possibility with the recent warm temperatures. Backcountry recreationists are encouraged to avoid slopes and stay out from underneath slopes >35 degrees on all aspects below 8500ft. In the alpine above 8500ft recreationists should avoid wind-loaded terrain features on N-E aspects >30 degrees and cross-loaded terrain features mid-slope. Recreationists should also stay out from underneath overhanging cornices and stay far back from the edges of overhanging cornices. Travel on the windward side of ridges looking for firm signs of solid earth like trees and exposed rocks. Conservative route selection and travel protocols are a must.

SPECIAL ANNOUNCEMENT:

We are now offering the Kip Rand Memorial Hat as a way to remember the former director of the Wallowa Avy Center. Kip was a great friend and a great director. These commemorative hats can be purchased for $25 or free with a $50 donation. You can go to www.wallowaavalanchecenter.org and click the Donate Now button and pay via Pay Pal (insert that you want a Kip hat in notes), or you can send a check to PO Box 324 Joseph, OR 97846 and leave a note. Remember Kip Rand and help support the WAC. We have sold nearly 200 Kip Hat’s thus far and another 100 were just ordered!

Recent Activity

Numerous loose wet slides were observed and reported in the Wallowa and Elkhorn mountains on a variety of aspects and elevations below 8500ft. over the last several days. WAC Director, Victor McNeil reported touchy wind slabs on cornices 8-12" thick breaking out on leeward terrain features in the alpine in McCully Basin in the northern Wallowa mountains yesterday.

Current Conditions

It's spring time and we have a tale of two snowpacks - and it's all about elevation, folks. Snow levels over the last several days have been hovering between 8500 to 9,000ft. This means areas below 8500ft. have been getting precipitation mostly in the form of rain and and areas above 8500ft. getting precipitation largely in the form of snow. The snowpack below 8500ft. is wet down 3ft. or more in many mountain locations. Areas above the snow line have received 4-6" of new snow in the last 48 hours. The winds have been strong at upper elevations with Mt. Howard (8000') reporting SW winds 20-30mph, gusting 40's. Temperatures have cooled down with a weak cold front passing over our area today through early Friday. This will allow the snow level to drop down to near 5000' through early Friday. Another significant warm front will roll in late Friday afternoon. This will lead to rising snow levels (8500') and temperatures. Mountain locations can expect anywhere from .5 to .75 inches of precipitation with most of this falling as rain below 8500ft. Friday night into Saturday morning. Upper elevations will likely see 6-8" of new snow. Winds will increase out of the SW to 20-30mph, gusting 40's. This warm front will be quickly followed by a cold front which will drop temperatures dramatically and lower snow levels down to 4,000ft. by early Sunday morning. Lows Sunday morning look to be in the teens to low 20's with a solid freeze occurring at all elevations. A weak ridge builds on Sunday with isolated snow showers and little precipitation expected. The reprieve is short lived as another storm system is on track to impact our area on Monday and through the middle of next week.


Avalanche Problem #1

ASSESSMENT
As I stated above it is a tale of two snowpacks. At elevations below 8500ft precipitation the last several days has largely come in the form of rain. Most mountain locations have not seen a solid freeze in 3 days. The snowpack below 8500ft is wet and saturated at several layers down to 3ft or more. Temperatures are dipping down, finally, below 32 degrees this morning around 4am, but this will not be enough of a freeze to lock things up. The problem with rain on snow is that it percolates down through the snowpack and pools at and saturates the snowpack around more impermeable or dense layers like crusts. This weakens the snowpack at these layers and creates instability. With some of these saturated layers existing above melt-freeze crusts down three feet or more there is a chance that an avalanche initiated in an upper layer could step down to a deeper buried weak layer and create a large and destructive avalanche. Another round of rain on snow is expected on Friday evening through early Saturday morning below 8500ft. This will continue to saturate and weaken the snowpack and create unstable conditions. Loose wet and wet slab avalanche activity is possible. Recreationists are encourage to avoid slopes >35 degrees and stay out from underneath steep slopes and overhanging cornices. Recreationists should also avoid traveling under or on overhanging cornices since many have likely been weakened by the recent warm temperatures. This weekend is a good opportunity to do some other spring time activities - like take a hike, spring clean, bake cookies, fix up the bike.


TREND

Same over next 48 hours hours
LIKELIHOOD

SIZE

Avalanche Problem #2

ASSESSMENT
Mountain locations above 8500ft have been getting precipitation the last several days largely in the form of snow with 4-6" or more of new snow reported. Winds have been strong out of the SW 20-30mph, gusting into the 50's. This has created sensitive wind slabs 8" to 12" or more in depth on N-E aspects above 8500ft and on cross-loaded leeward terrain features mid-slope. With the addition of another 6-8" of new snow forecasted for Friday night and strong SW winds 20-30mph gusting into the 40's the likelihood of a skier, rider, or snowmobiler triggering a wind slab is likely. Backcountry recreationists are encouraged to avoid wind-loaded terrain features on N-E aspects above 8500ft >30 degrees and stay off and out from under overhanging cornices. Cornices have likely been weakened by the recent warm temperatures and can break back onto ridge tops. To avoid cornice fall stay way back from cornice edges by traveling on the windward side and look for signs of solid ground like trees and exposed rocks.
TREND

Increasing over next 60 hours hours
LIKELIHOOD

SIZE

Mountain Weather

fwus46 kpdt 201056
 sagpdt
 
 avalanche guidance
 national weather service pendleton or
 356 am pdt sun aug 20 2017
 
 orz050-210100-
 wallowa mountains 8000 to 9000 feet-
 356 am pdt sun aug 20 2017
 
 .today...sunny. light winds. highs 54 to 61. 
 .tonight...clear. north winds around 10 mph in the evening becoming
 light. lows 37 to 44. 
 .monday...sunny. light winds. highs 60 to 67. 
 .monday night...clear. light winds. lows 43 to 50. 
 .tuesday...sunny. light winds. highs 67 to 74. 
 .tuesday night...clear in the evening, then partly cloudy with
 slight chance of thunderstorms after midnight. light winds. lows
 44 to 51. 
 
 

General Annoucement

The Wallowa Avalanche Center issued an Avalanche Warning for the mountains of Northeast Oregon. This warning expires Thursday at 1:00 AM. Discussion: Recent warming temperatures combined with rainfall above 8000 feet has created unstable snow conditions. Numerous natural avalanches have been observed. Rain on snow destabilizes the snowpack and can lead to large avalanches. Cornices will also become less stable and can collapse, triggering deep instabilities in the snowpack. Travel in and around avalanche terrain is not recommended.


DISCLAIMER: This advisory does not apply to developed ski areas and avalanche terrain affecting highways.