THIS AVALANCHE ADVISORY EXPIRED ON February 19, 2017 @ 5:59 am
Avalanche Advisory published on February 18, 2017 @ 5:59 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Danger is Moderate today. High Southerly winds Thursday created a new batch of wind slabs on mostly Northerly aspects above 7000 ft.  These new slabs and 3-5 inches of new snow fell on a variety of  slick, old snow surfaces which will create poor bonding in many places. Below 7000 feet there is a possibility of wet loose avalanches due to another day of near or above freezing temperatures and the possiblity of rain on snow.  

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 are the theme of the week again this week.  Thursday's wet and windy storm left a new batch of stiff but sensitive wind slabs across the upper elevations.  Wind directions were mostly out of the South so expect to see the most loading and wind slabs on the Northerly aspects.  Pay attention to snow conditions if you are approaching any steeper terrain though, with winds as strong as we had Thursday there are plenty of areas of localized wind loading on smaller terrain features below the ridgelines and in any pocket that could catch the blowing snow.  Watch for visual clues of wind affected slopes, tree spines, drifts and pillows are all pretty obvious. These new wind features have all been deposited on a highly variable old snow surface. Wednesday we found very firm rain and sun crusts on all but the most protected, high elevation slopes. The new wind slabs were showing signs of instability over the last 2 days in some areas as they produced shooting cracks under the weight of a skier near the ridgetops.  

Cornices are VERY large and unpredictable right now, avoid travel on heavily corniced ridgelines.  Use rocks and vegetation as a reference to where overhanging snow begins and terra firma ends. If you are beyond the last row of ridgetop trees, you are probably on a cornice.  Additionally, new snow today through Monday will likely add quite a bit of new snow to the game as well so watch for the growth of poorly bonded storm slabs at all elevations as we get additional snow.

Avalanche Problem 2: Loose Wet
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Lower elevation temperatures were still above freezing this morning at 5 am. Snotel sites between 6200 and 6500 feet were showing temperatures at or just above freezing.  In addition,  the rain line will climb to right around the 6500 foot level today.  Yesterday, slopes below 7000 feet got warm and sloppy, roller balls and shallow wet, loose sluffs were coming off of our ski turns in 30 degree terrain.  The possibility of wet, loose avalanches on steep, lower elevation terrain will stick around for the next few days as day time high temperatures exceed 35 degrees and lows hover near the freezing mark. Precipitation in the valleys is going to be mixed as well with freezing lines between 4000 and 6500 feet over the next few days with several waves of moisture coming in.  As the snowfall accumulates the size of the wet slides is going to increase.  If you are notice a sudden change in the ability of the snowpack to support your weight or the weight of your machine   (you start sinking through the top layer) it is definately time to find cooler or low angle slopes.

advisory discussion

Snowmobiler/Snowbiker Travel Restrictions: Granite Mountain Area Closure is in effect Jan15-March 15, 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,  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").

 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 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. 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

Patches of very firm snow can still be found on all but the most shady aspects. Last week's rain crust is now a stout 3-6 inch crust in most places, the 2-5 inches of new snow was sticking pretty well to the old snow surface but on slopes over 35 degrees yesterday but it wasn't enough to keep you off the crust.  Also, it was fairly easy to get small pockets of shallow wet, loose debris to move below 7000 ft.  Ski turns and cuts produced similar results on even lower angle terrain. In a confined area or on a very steep slope these would probably pack enough punch to steer a skier where they don't want to go. Over the next 24 hours, the upper elevations could pick up close to a foot of new snow, pay attention to the bonding of the new snow before committing to any steep slopes.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 27 deg. F.
Max. temperature in the last 24 hours: 27 deg. F.
Average wind direction during the last 24 hours: E/SE
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: inches
Total snow depth: 60 inches
weather

SHORT TERM...Today through Sunday...Precipitation will continue today across the entire area ahead of a weak upper level trough. The heaviest precipitation looks to remain across the Camas Prairie through the West Central and Boise Mountains favoring south- southwesterly slopes. The upper level trough will move through the forecast area later this evening for a brief break in the precipitation. Snow levels right around 5000 feet this morning with temperatures at Bogus Basin, McCall and Lowman at or just above freezing were wet snow was falling at 09z. Expect areas under 6000 feet to change to rain after sunrise. Moderate southeasterly winds will continue mild temperatures in the valley and high snow levels over the mountains through Sunday. Another weak trough moves on shore Sunday bringing another round showers to the region. The later trough passage timing of Sunday afternoon favors better instability for more convective showers and possible a few thunderstorms in Southwest Idaho. 

LONG TERM...Sunday night through Saturday...Very active wet pattern on tap throughout the period. First wave of precip comes in southwest flow aloft for Monday through Tuesday, and has snow levels near 5000 feet MSL to the north sloping to 7000 ft MSL to the south, so should be rain for valleys. Wednesday into Thursday an upper- level trough passes by, and snow levels drop dramatically, with snow levels dropping to the valley floors by late Wednesday or early Thursday. Looks like most precip has moved off to the east by the time snow reaches the valley floors, but timing is slightly different in the models, so this bears watching closely. Models then start to diverge with the evolution of a short wave off the West Coast, which leads to large differences in the flow pattern over the area by Friday and Saturday. ECMWF solution would be colder and slightly drier, and GFS solution would be wetter, but slightly warmer. Have just kept the forecast temperatures pretty steady with a chance of precip in most areas until the pattern for this period becomes more clear.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Rain and snow, becoming all rain after 11am. High near 40. South southeast wind around 8 mph. Chance of precipitation is 100%. Little or no snow accumulation expected Rain showers before 11pm, then rain and snow showers likely. Low around 30. South wind 3 to 7 mph. Chance of precipitation is 100%. New snow accumulation of less than a half inch possible. Snow showers. Some thunder is also possible. High near 38. South wind 5 to 9 mph. Chance of precipitation is 80%. New snow accumulation of less than one inch possible.
Temperatures: 40 deg. F. 30 deg. F. 38 deg. F.
Wind direction: SSE S S
Wind speed: Around 8 3-7 5-9
Expected snowfall: 0 in. Trace in. Trace in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow. High near 31. South wind 15 to 18 mph. Chance of precipitation is 100%. New snow accumulation of 2 to 4 inches possible. Snow showers. Low around 23. South southwest wind 7 to 15 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 7 inches possible. Snow showers. Some thunder is also possible. High near 28. South southwest wind 9 to 14 mph. Chance of precipitation is 80%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 31 deg. F. 23 deg. F. 28 deg. F.
Wind direction: S S SSW
Wind speed: 15-18 7-15 9-14
Expected snowfall: 2-4 in. 3-7 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.