THIS AVALANCHE ADVISORY EXPIRED ON January 16, 2020 @ 6:53 am
Avalanche Advisory published on January 15, 2020 @ 6:53 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche danger is Considerable in the upper elevations. Strong winds and light new snow have formed Wind slabs and storm slabs.  Loose dry snow Avalanches or sluffs are possible on all sunny and steep terrain today.  The most sensitive snow lies in the upper snow pack, but you could trigger an avalanche in older weak layers that are now buried 3-5 feet deep or more.

 

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

New wind slabs and storm slabs have continued to grow with the sustained new snow and winds gusting upwards of 20 mph.  The forecast is calling for gusty SSW winds upwards of 20 mph today. Be cautious and avoid wind loaded terrain.

Light density snow is easily transported by the wind and can result in widespread wind loading.  You are MOST likely to find wind slabs near ridge lines and on cross loaded slopes(think gullies and sub-ridges) in the upper elevations but today wind slabs and new storm slabs are going to be even more widespread.  A combination of new surface hoar growth mid week, light density snow from Wednesday and Thursday and over a foot of new snow will create some very touchy conditions on all steep slopes today. 

Look for wind affected areas, notice changes in the density of the snow surface and recognize red flags like cracking or collapsing under your skis or sleds.  Today is the day to use good travel protocols, do not put more than one person on a slope at a time and avoid steep terrain.

Avalanche Problem 2: Loose Dry
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Today, the Sun could get some snow to loosen up on rocks and steep slopes. Loose point releases are possible if we do get some Sun on East, South and West slopes, but overall loose powder on steep slopes is you biggest concern.

The snow has been coming down and its consistency has made a lot of people happy. The upper loose dry snow will take some time to consolidate given the forecasted cold temperatures, Loose snow sluffs/avalanches will likely run with you in steeper terrain, or probably anywhere you can get going, the snow can too. The loose snow can be a non-issue until it sends you into rocks, or trees, or tree wells, or just buries you all together. Big sustained steeper slopes should be aproched with slough management in mind.

Tree well danger is growing too. The loose dry snow could send you deep into a tree well. Keep eyes on your partners, and be cautious near trees.

Avalanche Problem 3: Persistent Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Deep in the snow pack we still have a couple of suspect persistent weak layers responsible for human triggered avalanches that deserve our respectful monitoring. Both weak layers have shown good trends in strengthening. Buried surface hoar in the mid-pack, and basal facets around a crust near the ground. We haven't seen anything being triggered on the weak layers in a couple weeks, but a lot of snow and wind with poor visibility for over a week has kept anyone from getting eyes on terrain. Mid storm, Payette powder guides reported seeing some natural avalanches in a brief break in the storm.

 

 

advisory discussion

Let us know what you are seeing out there.  It helps us paint a better picture of the current conditions across the West Central.  It's easy to do, takes about 5 minutes and prompts you for pertinent snow and avalanche info.  If you see an avalanche, note the direction the slope faces, relative elevation, depth of the crown and try to get a pic if possible.  Your observations can make a difference.    Submit avalanche observations       Submit snowpack observations

recent observations

Yesterday, we hiked up Granite mountain on skis to our weather staion at 7800 feet. The snow was way too deep to allow our 600's to climb the mountain. At 7800 feet near the Granite weather station we found 35 more inches of snow from a week ago. The depth sensor should display a depth of 84 inches (doubling our snow pack in just over a week). Our pit tests gave no results, and we did not experience any red flags as far as cracking or whoomphing below 8,000 feet. While hiking up the South East shoulder, nearing the summit we were able to stomp with our skis on a steep, 6-10 inch thick wind slab and get it to fail fairly easy. We skied a couple steep E& ENE slopes and had some managable small sluffing take place. Overall the snow quality and the coverage is excellent, and stability is pretty good in most places below 8,000 feet. Visibility above 7, 000 feet has been poor, and not allowed us to get eyes on some of the bigger peaks where we know natural avalanches have taken place.

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 2 deg. F.
Max. temperature in the last 24 hours: 12 deg. F.
Average wind direction during the last 24 hours: S
Average wind speed during the last 24 hours: NA mph
Maximum wind gust in the last 24 hours: NA mph
New snowfall in the last 24 hours: NA inches
Total snow depth: 40 inches
weather

 

Area Forecast Discussion
National Weather Service Boise ID
250 AM MST Wed Jan 15 2020

.SHORT TERM...Today through Friday...A dry start to the forecast
period expected with a near zonal flow across the area. An
approaching area of low pressure will send moisture over the area
this afternoon, bringing a return of snowfall across the higher
terrain of Baker County, OR and across the Boise and West Central
Mountains. Snowfall associated with this initial moisture push
anticipated through Thursday morning. Additionally, a tightened
pressure gradient tonight will lead to the development of gusty
to breezy wind across the Treasure Valley which looks to continue
into Thursday morning. The strongest wind looks to be southeast
of Boise. The cold front associated with the previously mentioned
low pressure system will move into the area Thursday, bringing
snowfall with it. This activity will spread to include much of the
forecast area Friday morning. Numerical guidance indicates the
cold front and its snowfall moving further east on Friday morning,
reaching mostly outside the forecast area by the afternoon.

.LONG TERM...Friday night through Wednesday...A building high
pressure ridge over the Intermountain Region will deflect the next
Pacific weather system north as it approaches the coast Friday
night. Some of the moisture associated with this system will drift
inland, bringing scattered snow showers Saturday and Saturday night.
On Sunday the amplifying ridge will end the precipitation, except
for lingering snow showers over the central Idaho mountains. As the
ridge moves east of our area on Monday, precipitation chances will
increase in advance of the next weather system. As it moves inland
Tuesday and Wednesday, it will bring more snow to the mountains,
with a mix of rain and snow in the valleys below 4000 feet.
Temperatures will warm from near normal on Saturday to 5-10 degrees
above normal on Wednesday.

&&

.AVIATION...Mainly VFR today. An approaching upper level trough will
bring increasing surface wind this afternoon and snow across Baker
County Oregon and the central Idaho mountains tonight. Surface winds
east to southeast 5-10 kts this morning increasing to 10-20 kts this
afternoon. Winds aloft at 10k ft MSL southwest to west 30-40 kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Increasing clouds, with a high near 24. Wind chill values between -6 and 4. South southeast wind 5 to 14 mph. Snow likely. Cloudy, with a low around 21. South southeast wind 9 to 13 mph. Chance of precipitation is 60%. New snow accumulation of 1 to 2 inches possible. A 40 percent chance of snow, mainly after 11am. Cloudy, with a high near 34. South southeast wind 6 to 8 mph. New snow accumulation of less than one inch possible.
Temperatures: 24 deg. F. 21 deg. F. 34 deg. F.
Wind direction: SSE SSE SSE
Wind speed: 5-14 mph 9-13 mph 6-8 mph
Expected snowfall: 0 in. 1-2 in. Less than one in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: Partly sunny, with a high near 15. Wind chill values between -7 and -17. Breezy, with a south wind 9 to 14 mph increasing to 21 to 26 mph in the afternoon. Snow likely. Areas of blowing snow. Cloudy, with a temperature rising to around 23 by 3am. Wind chill values between -5 and 5. Breezy, with a south wind 22 to 26 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. A 50 percent chance of snow. Cloudy, with a high near 24. South wind around 18 mph. New snow accumulation of 1 to 2 inches possible.
Temperatures: 15 deg. F. 23 deg. F. 24 deg. F.
Wind direction: S S S
Wind speed: 9-26 mph 22-26 mph 18 mph
Expected snowfall: 0 in. 1-3 in. 1-2 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center. This advisory covers the West Central Mountains between Hard Butte on the north and Council Mountain on the south. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.