THIS AVALANCHE ADVISORY EXPIRED ON January 15, 2020 @ 6:34 am
Avalanche Advisory published on January 14, 2020 @ 6:34 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche danger is High in the upper elevations. Strong winds and light new snow have formed Wind slabs and storm slabs.  Loose dry snow Avalanches are likely on all 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


  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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New wind slabs and storm slabs have continued to grow with the sustained new snow and winds gusting upwards of 30 mph.  The forecast is calling for another 3-7 inches of snow and gusty SSW winds upwards of 20 mph today. Tonight, the winds are forecasted to calm down, and the snow is going to finally give us a break for 24 hours. The wind slab and storm slabs will take some time to heal, so 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
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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.

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
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Deep in the snow pack we still have a couple of suspect persistent weak layers that deserve our respectful monitoring. We haven't seen anything being triggered on the weak layers in a while. This is the storm we have been waiting for to give those layers a real test. 

We have been tracking these layers through the snow pack as well as how widely distributed they are throughout the terrain.  The short version of the story is that we have a relatively complex snow pack with multiple weak layers that are widely distributed.  We would need a crystal ball to accurately predict how these layers are going to react to the load of fresh and wind blown snow that is getting added right now. 

What we can accurately say is that this is the biggest storm cycle of the winter  so far and the probability of natural and human triggered avalanches is going to be increasing as the snow piles up.  Give the snow pack some time to adjust right now and avoid traveling on or near slopes that are steep enough to produce avalanches.  

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

Visibility as well as travel has been difficut the higher you get in elevation. We had a report from Payette Powser Guides that travel in the Lick Creek drainage has been difficult due to the deep snow over the last few days. Natural avalanches went during the storm which was visible during a brief break. They reported some loose snow sluffing while skiing, and not being able to ski lower angle terrain.

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: 13 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
330 AM MST Tue Jan 14 2020

.SHORT TERM...Today through Thursday...The final phase of ongoing
winter storm will wrap up today as upper low along the coast
moves inland. With passage of the warm front overnight,
precipitation will be more showery in nature today with less
coverage across lower elevations. The dynamic upper low center
tracks through the region late this afternoon/evening likely
bringing some stronger precipitation bands with it. Brief heavy
snow/graupel and gusty winds could accompany the late day showers.
Outside of localized shower activity, accumulations will be light
across Baker county and the upper Weiser River basin today, so
have ended the winter weather hazards for those zones. Also with
the late afternoon/evening arrival of the upper low have extended
the Winter Storm Warning for the mountains into this evening.
Drier air moves in quickly tonight as the low tracks eastward,
allowing for clearing skies. Lows Wednesday morning will be
notably colder than recent nights, especially given the fresh
snowpack for many locations. Wednesday is cold and breezy as a
shortwave ridge builds along the Continental Divide in advance of
deepening offshore trough. A warm frontal passage introduces
light snow to e-central Oregon and the w-central Idaho mountains
Wednesday night, while southwest flow behind the front will
maintain shower development in the mountains through Thursday.
Precipitation chances increase across southeast Oregon on Thursday
as the upper trough begins to move inland. Lower elevations of
southwest Idaho are mostly dry after today. Temperatures are at or
below normal today and Wednesday with several degrees of warming
on Thursday.

.LONG TERM...Thursday night through Tuesday...An active and
progressive weather pattern will continue through the weekend and
into the first of next week. Several disturbances are forecast to
move through the area, with a focus on early Friday, late Saturday
and again on Tuesday. The best chances for precipitation will be
over the mountains, however, valley locations stand a good chance
of experiencing snowfall early Friday. Temperatures will be near
normal through the period.

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.AVIATION...VFR will be the general rule, except for in and around
snow showers through the day today. The best chance for showers
and reductions in category will be over mountain areas, and at
KJER and KTWF, especially through 15Z. Surface winds, southeast
10-15kts becoming west to southwest 10-15kts with gusts 20kts
after 12Z. Winds aloft to 10k feet MSL, westerly 35-45kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow showers. High near 25. South southwest wind 5 to 9 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible. Snow showers likely before 11pm. Mostly cloudy, with a low around 3. Southwest wind around 6 mph becoming calm after midnight. Winds could gust as high as 26 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible. Increasing clouds, with a high near 20. Light southeast wind becoming south southeast 5 to 10 mph in the afternoon.
Temperatures: 25 deg. F. 3 deg. F. 20 deg. F.
Wind direction: SSW SW SSE
Wind speed: 5-9 mph Gusting 24 mph 6 mph Gusting 26 mph 5-10 mph
Expected snowfall: 1-2 in. Less than one in. 0 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow showers. Areas of blowing snow after 11am. High near 13. Wind chill values between -6 and zero. Southwest wind around 11 mph, with gusts as high as 23 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible. Snow showers likely before 11pm. Areas of blowing snow before 11pm. Mostly cloudy, with a low around 0. Wind chill values between -7 and -16. Southwest wind 6 to 13 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible. Increasing clouds, with a high near 11. Wind chill values between -8 and -15. South wind 7 to 17 mph.
Temperatures: 13 deg. F. 0 deg. F. 11 deg. F.
Wind direction: SW SW S
Wind speed: 11 mph, Gusting 23 mph 6-13 mph 7-17 mph
Expected snowfall: 2-4 in. 1-2 in. 0 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.