THIS AVALANCHE ADVISORY EXPIRED ON February 27, 2017 @ 7:04 am
Avalanche Advisory published on February 26, 2017 @ 7:04 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Danger is MODERATE above 7000 feet today on wind affected slopes. Winds gusting around the compass over the last 5 days have left multiple layers of wind slabs sensitive to the weight of a skier or snowmobiler scattered across exposed, upper elevation terrain. The Avalanche Danger below 7000 ft where soft snow exists on protected slopes is LOW.  Very firm conditions will be found in the lower elevations. 

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Wind slabs have been our main avalanche concern through most of the last week.  After a mostly calm day yesterday, winds shifted around to the W and WSW overnight with gusts in the 20+ range. Throughout the last week we have seen winds in excess of 30 mph from a variety of directions.  Expect multiple generations and layers of wind slabs on upper elevation, wind exposed terrain today. Shallow, and sensitive wind slabs may be found below ridgetops, in gullies or other small terrain features on most upper elevation slopes. Over the last week, these wind slabs have been responsible for several human triggered avalanches as well as a substantial natural avalanche cycle.  In most areas, the weak layers are in the upper 45 cm (18 in) of the snowpack.  Several of the recent avalanches were triggered in these shallow layers and then "stepped" down or were able to propagate down through some dense snow to the February 9 rain crust(see photo below).  In some areas this week we have also found a layer of rounding facets above this crust which is giving us hard results but very clean shear planes in our pit tests.  

Also, keep in mind that cornices are very large and overhanging right now.  Avoid traveling past the vegetation line on any corniced ridgelines right now, if you go past the trees, you are probably on overhanging snow. We have seen some very large cornice failures over the last few weeks.

 The good news is that not only are these wind affected areas not where you want to be skiing or riding right now but they are also easy to recognize;  wind sculpted, textured or scoured northerly slopes are easy to pick out visually. Also, plenty of soft, deep snow will be found out of these exposed areas and lower down in wind protected terrain.  The bad news is that starting later this morning,  SSW winds are going to continue to ramp up with an approaching storm system settling in for the first half of the week.   3-5 inches of snow is forecasted for today which is going to start camouflaging our current wind slab problem and add some new snow for yet another round of fresh wind slab to start forming. Expect the avalanche danger to rise through the afternoon today and tomorrow as the new snow starts to accumulate.

 

advisory discussion

Snowmobiler/Snowbiker Travel Restrictions: Please respect these closures and other users recreating in them.  Winter Travel Map(East side). You can download the map to the AVENZA app on your phone, and know your exact location while you are out riding.  It is your responsiblity to know where closures exist on the forest.

The Granite Mountain Area Closure is in effect Jan15-March 31, please respect Snowcats operating in this and nearby areas.  In addition there are other areas on the Payette National Forest that are CLOSED to snowmobile traffic including Jughandle Mt east of Jug Meadows, North of Boulder Mtn, East of Rapid Peak, North of the 20 mile drainage, Lick Creek/Lake Fork Drainage (on the right side of the road as you are traveling up canyon), and the area north of Brundage Mt Ski area to junction "V" and along the east side of Brundage and Sergeants' Mts. with the exception of the Lookout Rd( junction "S").

The Friends of the Payette Avalanche Center (FPAC) needs YOU! We are in desperate need of more user support and financial assistance. The avalanche forecast is not a guaranteed service, and is in jeopardy of dwindling down to only a couple of days a week in the near future.We have equipment that is overdue for replacement but lack the funds to purchase new gear including weather station parts and our forecast sleds.  Please help if you can by clicking the DONATE tab above. If you value this life saving information, make a donation or help the FPAC in raising funds for the future.

recent observations

Several Northerly slopes failed earlier this week producing large avalanches down to a weak layer near the Feburary 9th rain crust.  Skiers and Snowmobilers were able to trigger shallow wind slabs and storm slabs in many places as well. While these slabs have begun to stabilize over the week, avoiding steep, easy to spot wind affected terrain is going to be your most prudent choice today.  Small sluffs or loose, dry avalanches are also a concern on steep slopes.  Cornices have also continued to grow over the last week and we are seeing some of the bigger cornices we have seen in a few years on the ridgetops.  Avoid heavily corniced areas as these monsters are really unpredictable right now.

A good practice and route finding excercise is to consider the consequences of something breaking before you get out on steeper terrain. What kind of slope is it?  Where would an avalanche take you? Are there trees or rocks below? Is there an escape route available? Play it safe in wind affected terrain and enjoy all of the soft deep snow on protected aspects.  Sledders and skiers will find plenty of fresh snow out there right now.

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 10 deg. F.
Max. temperature in the last 24 hours: 14 deg. F.
Average wind direction during the last 24 hours: WSW
Average wind speed during the last 24 hours: 5 mph
Maximum wind gust in the last 24 hours: 20 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: 68 inches
weather

SHORT TERM...Today through Monday...Cold upper trough will carve out a position over the Pac NW through Monday. Energy dropping into the trough along with afternoon instability will keep a chance of showers over much the area, though the focus of more continuous snowfall will be across the east-central Oregon and central Idaho mountains. Highest accumulations still look to concentrate over the west-central Idaho mountains with slightly lesser amounts in Baker county, the Weiser basin and Boise mountains. Further to the south, to include the Snake Plain and southeast Oregon, precipitation amounts will be light, totaling a tenth of an inch or less through Monday. Snow accumulation will generally be limited to sites above 4k feet during the daylight hours, though temperatures Sunday night will be cold enough to support accumulations at all elevations. Any snowfall Sunday night in the lower basins and valleys will be sporadic and light, with less than an inch for sites that see snow. The advisory for the west-central Idaho mountains remains in place, while rest of area stays below criteria. Winds pick up today ahead of the trough, adding a windchill to the well below normal temperatures. Winds are lighter tonight and Monday, but temperatures will remain around 10 degrees below normal.

LONG TERM...Monday night through Saturday...Models still have the cold upper level trough exiting east of our area on Tuesday, followed by cool northwest flow aloft through Thursday. There will be enough moisture embedded in this flow for snow showers over the mountains of Baker County Oregon and central Idaho, but the remainder of our area is expected to be dry. Friday through Saturday a Pacific weather system will spread precipitation across our area. There will be a gradual warming trend through the period, and temperatures will be close to normal Friday and Saturday, with snow levels rising to around 5000 feet.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: Snow showers. High near 26. South wind 6 to 11 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 1 to 3 inches possible. Snow showers. Low around 18. South wind 5 to 8 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible. Snow showers. High near 26. South wind 5 to 7 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 26 deg. F. 18 deg. F. 26 deg. F.
Wind direction: S S S
Wind speed: 6-11 5-8 5-7
Expected snowfall: 1-3 in. 1-2 in. 1-2 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: Snow showers. High near 20. Wind chill values between -6 and 4. Breezy, with a south wind 16 to 22 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 3 to 5 inches possible. Snow showers. Low around 12. Wind chill values between -6 and 4. Southwest wind 9 to 18 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible. Snow showers. High near 19. South southwest wind 5 to 10 mph. Chance of precipitation is 80%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 20 deg. F. 12 deg. F. 19 deg. F.
Wind direction: S SW SSW
Wind speed: 16-22 9-18 5-10
Expected snowfall: 3-5 in. 3-5 in. 2-4 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.