THIS AVALANCHE ADVISORY EXPIRED ON March 10, 2017 @ 7:50 am
Avalanche Advisory published on March 9, 2017 @ 7:50 am
Issued by Dave Bingaman - Payette Avalanche Center
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The Avalanche Danger is CONSIDERABLE today at all elevations due to natural avalanches being possible, and human triggered avalanches being likely.  Dense snowfall, moderate S and SW winds, and warming temperatures will cause the avalanche danger to increase through the day as the snowline rises to almost 8000 ft.  1-3 ft thick wind slabs and storm slabs are the main concerns today and will become more likely as the upper snowpack becomes saturated by high elevation rain starting this afternoon.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Storm Slab
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Over the last week, the West Central has received between 40 and 48 inches of snow.  Most of this snow was cold smoke with temps in the teens.  Local ski resorts have reported up to 12-19 inches in the last 2 days and this snow came in with warming temperatures and more wind. This new snow is warmer and heavier, and has now created an upside down snowpack. The surface will be much denser than the older snow beneath it, making for challenging skiing and riding conditions. Human triggered avalanches will be likely as we now have a classic bad recipe of a strong layer over a weak layer. 

Avalanche Problem 2: Wind Slab
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Winds have primarily out of the SW over the last 24 hours and gusted to near 30mph yesterday in the Northern portion of the  PAC advisory area. We found shallow wind slabs that were sensitive to the weight of a skier in these areas on Tuesday near the ridgetops which continued to grow yesterday.  Tamarack Ski Patrol reported winds in the 40-50mph range yesterday all of which have been doing a fair job of loading Northern aspects, creating wind slabs near the ridgelines. Tamarack Ski Patrol also reported very large cornice growth on the West Moutain crest Tuesday night with impresssive results in the wind slab below the cornice from avalanche control work yesterday.  Terrain features help to create swirl and thus cross-load, and load various aspects, not just the Northern aspects.  Avoid heavily corniced areas and potential wind slabs near the ridgetops.

Avalanche Problem 3: Loose Wet
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Rain on snow, coupled with some of the winter's warmest temperatures is in the forecast for this afternoon, tonight and through the early part of the day tomorrow.  Temperatures are already above freezing at local snotel sites at 6500 feet.  The snowline is forecasted to rise to near 8000 feet with a strong pulse of moisture on tap over the next 24 hours.  Expect to see increasing roller ball and loose wet avalanche activity through the day and into the evening tonight.  The potential for wet slab avalanches will also increase as rain saturates the upper snowpack.  Avoid steep slopes once the rain begins and pay attention to changing conditions as the snowpack warms today.

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, signed and unsigned closures and other users 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").

                                 

Photo 1 is from the edge of the signed Brundage Mt. ski area closure just past the parking lot, photo 2 is of sled tracks ignoring Catski terrain signs...there is alot of snow out there folks please respect closures and other users.

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

We found challenging climbing conditions yesterday on snowmobiles as we struggled to get to our Granite Mountain Weather Station.  6-18 inches of cakey, upside down snow challenged our 600s to give everything they had.  Mit pits and test pits showed several layers that failed in compression including a thick grauple layer located about 6 inches down in the snowpack.  We also had consistent, moderate results in our pits at the grauple layer and at the interface between the older, cold snow and the 12-18 inches of new, warm, dense snow.  Our ECT propagated at 16 taps across the block at that interface. (see photo, failure is just above the shovel handle).  We were also surprised to find most of the 25 foot Granite Mt weather station tower now buried(photo 2).

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 28 deg. F.
Max. temperature in the last 24 hours: 28 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 13 mph
Maximum wind gust in the last 24 hours: 26 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

SHORT TERM...Today through Friday...Warm, moist, westerly flow
aloft will continue through early Friday, with most precipitation
north of the Boise area, and concentrated on west facing slopes,
with very little, if any, precip expected near the Nevada border.
Snow Levels reach nearly 8000 ft MSL tonight. See Hydrology
section for details of flooding concerns. On Friday, models are
bringing through an upper level wave slightly quicker. This wave
brings precip early Friday further south, into the Magic Valley
and south of the Snake River. But it pushes eastward out of the
forecast area by late afternoon.

LONG TERM...Friday night through Thursday...Upper level ridging
through the extended period keeps things mostly dry. A weak system
pushes up and over the ridge Saturday night and into Sunday bringing
chances of showers for the West Central and Boise Mountains. Snow
levels remain 6000 feet MSL or higher through the extended so rain
is the main player with just the highest of elevations seeing any
snow. After Monday models have some disagreements with timing and
placement of the next disturbances. Kept a mention of precipitation
chances in the forecast, mostly for the West Central Mountains. By
Wednesday night another more well developed frontal boundary begins
to push onshore. GFS is a little faster than the ECMWF with this
one, but overall placement among the models is not all that bad. An
increased chance of precipitation for all locations with this system
passing through on Thursday. Temperatures are above normal
throughout the period with temperatures beginning to show in the mid-
upper 60`s for the valleys by mid-week with a few models hinting at
70`s.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Thursday Thursday Night Friday
Weather: Rain. High near 40. South wind around 7 mph. Chance of precipitation is 100% Rain. Steady temperature around 41. South wind around 7 mph. Chance of precipitation is 90% Rain, mainly before 11am. High near 44. Southwest wind 5 to 8 mph. Chance of precipitation is 80%
Temperatures: 40 deg. F. 41 deg. F. 44 deg. F.
Wind direction: S S SW
Wind speed: 7 7 5-8
Expected snowfall: Rain in. Rain in. Rain in.
Granite Mountain at 7700 feet.
  Thursday Thursday Night Friday
Weather: Snow. High near 36. South southwest wind 10 to 14 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 2 to 4 inches possible. Rain and snow. Low around 31. South southwest wind around 15 mph. Chance of precipitation is 100%. Little or no snow accumulation expected. Snow, mainly before noon. High near 36. Southwest wind 10 to 14 mph, with gusts as high as 23 mph. Chance of precipitation is 90%. Little or no snow accumulation expected.
Temperatures: 36 deg. F. 31 deg. F. 36 deg. F.
Wind direction: SSW SSW SW
Wind speed: 10-14 around 15 10-14, with gusts to 23
Expected snowfall: 2-4 in. Trace in. Trace 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.