THIS AVALANCHE ADVISORY EXPIRED ON February 18, 2020 @ 7:31 am
Avalanche Advisory published on February 17, 2020 @ 7:31 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Hazard today is Moderate above 6,000 feet on slopes that receive direct Sun this afternoon, and wind loaded slopes steeper than 30 degrees. Below 6,000 feet the Avalanche Hazard is Low. Natural avalanches are possible, mainly on Southern and Western aspects that may get hot from the Sun. Human triggered avalanches are possible on upper elevation, wind loaded terrain.

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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The latest Storm pushed snow around and created some slabs that may be sensitive to the weight of a person. Be cautious as you climb up above 7,000 feet where the snow surface was exposed to wind, and on loaded lee slopes. The wind has swirled around from Northern and Southern directions, so pay attention to clues like sculpting, drifts, pillows, and Cornices. If you have red flags going off like cracking, hollow sounds, or woomphing, turn around and choose another area to play in.

Some of the large, gigantic Cornices in our mountains may be sensitive, and the may very well fail much further back than you think. Be cautious on the ridges, and give the edges room and the respect they deserve.

Avalanche Problem 2: Loose Wet
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 We are all anxiously waiting for the Sun. When the Sun comes out Today and Tomorrow, we will likely see some wet-loose, point release avalanches on slopes that are getting heated by the Sun. More than likely they will be small.

Avalanche Problem 3: Persistent Slab
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We have been finding some fragments of wind broken surface hoar, buried a little over a foot down from the snow surface, that was likely the culprit of a natural avalanche cycle that happened just towards the end of the last storm last weekend on North and East aspects. In out test pits throughout the advisory area this week, we have seen this layer producing moderate, broken failures in compression, and lacking the ability to propagate in extended column tests.  We feel like this layer has bonded well now.

We have a new snow load on top of surface hoar that formed during this past weeks awesome clear nights. We may very well see some natural avalanches this on this layer, and it may hang out and wait for a trigger like a snowmobile or skier in sheltered areas where the snow surface was protected from the Sun and wind this past week. 

Evaluate sheltered, steep slopes carefully this holiday weekend before committing to exposed, or big terrain. Buried surface hoar can be tricky, and when it propagates it can spread out fractures sometimes cross a whole ridgeline---we have to wait and see if this happens over the next 48 hours. Evaluate slopes carefully that are steep and protected, and definately spread out in steep terrain, use good safe travel protocols. We will be monitoring this problem closely over the next week.

Below is a photo of fresh Surface hoar at 7700 feet on a North aspect of Sgts Mountain Thursday afternoon.

advisory discussion

The Friends of the Payette Avalanche Center's Annual Fundraiser is this coming Friday, Februrary 21st at Banyons clubhouse on the McCall golf course. This year we will have a Silent Auction and Choose your own raffle prizes!  Live music by Jughandle Parade from 6-9!  Our goal this year is to raise $5000. which will go directly into additional forecasts for next season, our future forecasters scholarships and providing more Avalanche Awareness classes.  Tickets will be sold at the door.  $10.00 gets you in the doors with a raffle ticket.  Come on out and help make this years fundraiser this biggest yet!!

 

*Skiers and Snowmobiliers, the Granite Mountain closure went is in effect from January 15-March 31. Please respect Brundage Catski terrain closures which are CLEARLY marked on the west side of Goose Lake.  There is a shared use route at the northern end of the closure to allow access to Granite Mt Lookout and the upper east face of Granite Mt.  Additionally, public motorized use of ANY other Catski road is not permitted, including the roads between Brundage Reservoir and the East side of the Goose Lake Road in the Slab Butte and 76 areas. Please respect closed roads and areas and only ride on open roads and in open terrain.  There are also other areas that are closed to snowmobiling in the West Central Mountains. Click here for the Payette National Forest Winter Travel Map.

*Note to skiers accessing Jughandle Mountain from Silver Fox Trail.  Please park in signed areas only. Blocking or narrowing the road could result in loss of access to this area, ticketing or towing by Valley County.  There is NO parking allowed on the East side of the road or in the snowplow turnaround.  If you can't park in the signed area, park further down the road in a place where you are not obstructing traffi

recent observations

 

On Granite Mountain, North of McCall yesterday, we had various types of snow coming down on us, and a notable rhime crust that developed on the snow surface and our goggles during the morning hours. Later in the day the temperature dropped, and visibility improved. Our test pits and ski cuts did not produce much more than some minor sluffing in th new snow on steep descents. Visibility was good below 8,000 feet, but we were able to get a brief look at the peaks, which had wind effect on the snow surface from the Southeast winds. We observed some drifts that were 1-3ft deep. 

Staying lower in good visibility and out of wind loaded terrain in Twin Lakes

 

This may be some record sized graupel that was the dominant snow form that came down most of the day until the temperature dropped.

 

 

***If you are out in the mountains and see recent avalanches, please take advantage of the good visibility and snap a picture to submit on our Observations page.

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: 20 deg. F.
Average wind direction during the last 24 hours: SE
Average wind speed during the last 24 hours: 2 mph
Maximum wind gust in the last 24 hours: 13 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

Area Forecast Discussion
National Weather Service Boise ID
238 AM MST Mon Feb 17 2020

.SHORT TERM...Models bring one last short wave trough in from
western Canada today before clearing tonight. Latest models
have increased PoPs for today. NBM had been one of the drier
models but it has gradually increased PoPs with each new hourly
update and is now in line with MAV and MET PoPs. We have added
scattered snow showers to the forecast as far south as the Snake
Basin today, but little if any accumulation is expected there.
The Boise Mountains and west Central Idaho Mountains should get
1-3 inches, however. Then clearing tonight and becoming very
dry through Thursday. Clear skies, dry air, calming winds, and
new snow cover in many areas will provide ideal conditions for
strong radiational cooling the next several nights. Low temps
through Thursday morning will be in the single digits above and
below zero in the higher basins on the Idaho side, with generally
teens to lower 20s elsewhere. Highs will be in the upper 20s and
30s in the mountains, and upper 30s to mid 40s in the valleys.

.LONG TERM...Thursday Night through Monday...A high pressure ridge
over the Intermountain Region will keep our area dry through
Saturday. A trough of low pressure is forecast to impact the region
late Saturday night into Sunday. Models have backed off a bit from
previous runs, but it appears that this system is the next best
chance for precipitation. Snow levels will initially hover around
4000 feet before dropping to valley floors, meaning lower elevations
may see additional snowfall.

&&

.AVIATION...A weather system will spread clouds and showers along
with mountain obscuration into the area today. Eastern Oregon will
see impacts this morning, with much of Idaho seeing impacts late
morning into mid-afternoon. The terminals will generally be VFR,
with occasional MVFR/IFR in shower activity. Surface winds west to
northwest 10-20 kts. Winds aloft at 10k feet MSL west to northwest
40-50 kts.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Snow showers, mainly before 11am. High near 30. Calm wind becoming west northwest 5 to 7 mph in the afternoon. Chance of precipitation is 80%. Total daytime snow accumulation of 1 to 2 inches possible. Partly cloudy, with a low around 6. Northwest wind around 6 mph becoming calm in the evening. Sunny, with a high near 30. Calm wind.
Temperatures: 30 deg. F. 6 deg. F. 30 deg. F.
Wind direction: WNW NW Calm
Wind speed: 5-7 6 0
Expected snowfall: 1-2 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Snow showers. High near 17. Wind chill values between -1 and 4. Southwest wind 8 to 10 mph becoming northwest in the morning. Chance of precipitation is 90%. Total daytime snow accumulation of 2 to 4 inches possible. Partly cloudy, with a low around 4. Wind chill values between -5 and zero. North northwest wind 5 to 10 mph becoming east northeast after midnight. Sunny, with a high near 20. Wind chill values between -5 and 5. East wind around 6 mph becoming west in the afternoon.
Temperatures: 17 deg. F. 4 deg. F. 20 deg. F.
Wind direction: SW-NW NNW-ENE East
Wind speed: 8-10 5-10 6
Expected snowfall: 2-4 in. 0 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.