THIS AVALANCHE ADVISORY EXPIRED ON February 13, 2019 @ 5:52 am
Avalanche Advisory published on February 12, 2019 @ 5:52 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Hazard is High today.  Natural avalanches are likely and Human triggered avalanches are Very Likely. Over 2 feet of snow is forecasted and ridge tops will see gusts upwards of 30 MPH over the next couple days that will continue to create wind slabs.  It is also possible to trigger soft storm slabs in the upper 2 feet. Cornices are growing, and will likely fail.  Travel in, or near avalanche terrain is not recommended today.

How to read the advisory


  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Winter storm warnings are all over the weather feeds. The amount of new snow and 30 MPH wind gusts forecasted over the next few days is raising red flags. Wind slabs are growing, sliding, and re-forming daily. Natural wind slab avalanches have been observed over the last few days.  Travel in wind loaded avalanche terrain is not recommended.

 

 

 

Avalanche Problem 2: Storm Slab
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Be aware that a lot of new snow has fallen on a fresh crop of Surface Hoar and Near Surface Faceted snow ( recycled powder) on quite a few slopes. 

As the new snow accumulates over the next few days put your free for all goggles back in the bag and bust out the avalanche goggles to keep you safe. Practice safe riding and skiing, check your beacon batteries and keep your eyes on your partners. Pay attention to the slope angle and stay away from terrain over 30 degrees.

Avalanche Problem 3: Loose Dry
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While we are not recommending travel in avalanche terrain right now, if you did get on a steep slope, you should expect the new snow to run with you.  As we add more light density snow on what is already there, sluffing will increase in size and its ability to travel.

advisory discussion

PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.

Please be aware that there are areas that are CLOSED to motorized traffic in the McCall, Goose Lake and greater West Mountains area.  Just because there are tracks in some areas, does not mean they are open.  Please respect all users and closures.  See the Payette Winter Travel Maps for clarification.  Both the East and West maps can be downloaded on the Avenza app on your phone or are available at trailheads and local shops.   IT IS YOUR RESPONSIBILITY TO KNOW WHERE YOU ARE AND WHERE THESE CLOSURES EXIST.  

recent observations

Sunday, we toured the Pearl Lake area on the Crest line Trail above McCall. Opportunties for good photos were limited. The winter storm was in full effect with copious wind and new snow. The wind was gusting so hard at times that the visibility was non-existent. We observed some strong wind transport, and a couple of natural wind slab avalanches on leeward terrain that was getting a beat down with all of the wind scouring, sculpting and transport. Cornices were growing before our eyes. 

We were able to get a 1-2 foot wind slab to crack, break, and run with us on a small test slope with a cornice on our snowmobiles. The new snow was DEEP, and challenged us throughout the day. We were able to get some good loose sluffs  moving with us on steep slopes. Our test pits showed moderate results in the newer snow, and hard results with propagation on the older snow interface. Surface hoar was the weak layer in the shallower failures, and some near surface facets are still preserved enough to facilitate propagation with a hard load.

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 13 deg. F.
Max. temperature in the last 24 hours: 14 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: 22 mph
New snowfall in the last 24 hours: 18 inches
Total snow depth: 68 inches
weather

 

 

 

Area Forecast Discussion
National Weather Service Boise ID
312 AM MST Tue Feb 12 2019

.SHORT TERM...Today through Thursday...Snow continues to weaken
across the area this morning, with a lull in snowfall activity
anticipated through the early afternoon hours. Models showing a
return of snowfall over Baker County and the West Central
Mountains this afternoon, with activity steadily increasing
through the early evening. Generally widespread snowfall is
anticipated early Wednesday morning. Moisture associated with this
next push looks to be most impactful through Wednesday afternoon,
with weakened snow lingering into the overnight hours.
Temperatures across the area will warm, reducing the snow ratios
and raising snow levels across the area through Wednesday
afternoon. This combination is anticipated to bring a rain or rain-
snow mix across the Treasure Valley through Thursday. Snowfall
may be slightly more present across the Western Magic Valley on
Wednesday afternoon, but temperatures should keep accumulations
generally between 1 and 2 inches before temperatures convert
activity to a rain-snow mix on Wednesday night. The mountains of
central Idaho and Baker County are expected to see additional
snowfall of 10 to 15 inches, with localized amounts up to 20 to 24
inches. With these accumulations, the Winter Storm Warning
remains over these areas through Wednesday afternoon. Models
showing snowfall continuing into Thursday morning, with an
additional 2 to 6 inches over the mountains
and across Malheur and
Harney counties in Oregon.

.LONG TERM...Thursday night through Tuesday...Widespread rain
continues Thursday night under a mid-level trough before snow levels
quickly drop back down to the valley floor Friday afternoon. Snow
showers linger through the weekend with the greatest chance of
precip in the West Central Idaho Mountains. Northerly flow dries out
the region Monday while an approaching shortwave may stir up more
snow showers on Tuesday. Temperatures Friday will hover near normal
and will drop to 8-10 degrees below average through the end of the
period.

&&

.AVIATION...VFR. Local MVFR and mountain obscuration at KMYL in
light snow showers lingering through the morning. A brief break this
afternoon before another round of snow showers pushes in this
evening into early Wednesday. Surface winds: southeast-southwest 5-
10kts. Winds aloft to 10k feet MSL: southwest 45-50kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: A 40 percent chance of snow. Cloudy, with a high near 29. South wind 9 to 16 mph. New snow accumulation of less than one inch possible. Snow. Low around 24. South wind 10 to 14 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible. Snow. High near 30. South wind around 11 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 29 deg. F. 24 deg. F. 30 deg. F.
Wind direction: S S S
Wind speed: 9-16 10-14 11
Expected snowfall: Less than one in. 3-5 in. 3-5 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow likely, mainly after 11am. Cloudy, with a high near 18. Wind chill values between -2 and 3. Breezy, with a south wind 21 to 23 mph. Chance of precipitation is 60%. New snow accumulation of 1 to 3 inches possible. Snow. Low around 15. Wind chill values between -4 and 1. Breezy, with a south wind 18 to 23 mph. Chance of precipitation is 90%. New snow accumulation of 5 to 9 inches possible. Snow. High near 20. South wind around 18 mph. Chance of precipitation is 90%. New snow accumulation of 5 to 9 inches possible.
Temperatures: 18 deg. F. 15 deg. F. 20 deg. F.
Wind direction: S S S
Wind speed: 21-23 18-23 18
Expected snowfall: 1-3 in. 5-9 in. 5-9 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.