You are most likely to encounter sensitive wind slabs in the upper elevations, on leeward slopes, especially on Northern and Eastern aspects that have seen the most loading and have sizable cornices hanging above them. Yesterday, we observed natural wind slab avalanches in the Council Mtn area all were under cornices, North and East aspects...Look for the tell tale signs of wind effect like cornices snd other sculpting of the snow surface and choose your routes accordingly.
Our deep slab problem right now is the perfect definition of a LOW PROBABILITY/HIGH CONSEQUENCE scenario. The chance of triggering is going down and becoming more and more isolated but still lingering. Upper elevation slopes where early season snow was preserved is your likely best culprit. Add uneven rocky terrain into the picture and you are increasing the chance of finding that landmine trigger point. The size and density of the slab and the potential outcome of triggering one of these deep, persistent slabs is enough to keep me off of and away from the likely slopes. These are the same layers that have been responsible for fatalities near the West Central Mountains and in several other areas this winter.
We have been finding a well preserved layer of surface hoar 5 feet down in the snow pack on a high, north facing slope. In addition loose depth hoar and facets above and below the November crust that is now buried 7-8 feet down. We generally do not see problem layers like these persisting with a deep snow pack above them in this area.
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 traffic.
Yesterday, we covered a lot of terrain along the Council Mountain ridgeline. The wind was strong, gusting upwards of 30 MPH, and snowing pretty hard with some periods of limited visibility. We were able to see a lot of debris from cornice failures during our last warm-up. We also noticed a few small (R1D1-2) fresh natural wind slab avalanches that were about 6-12 inches deep on East and North aspect of Council, and other mountains just to its North. Our pits showed a poor to ok structure/strengthening snow pack. Our tests came out scoring moderately in the upper 2 feet of the snow pack, all of them on graupel layers that lacked propagation in Extended column tests. Some of the cornices on the East and North ridges are giant, bus sized hanging cornices.
Pit is at 7,000 feet, NNW aspect...the ground facets are damp and look fairly rounded under a lens. The mid-pack is the strongest, similar to what we have seen in other areas of the Payette.
Some of the graupel layers that were producing failures, and were likely culprits in the recent natural avalanches that we observed.
|0600 temperature:||16 deg. F.|
|Max. temperature in the last 24 hours:||24 deg. F.|
|Average wind direction during the last 24 hours:||NNW|
|Average wind speed during the last 24 hours:||7 mph|
|Maximum wind gust in the last 24 hours:||27 mph|
|New snowfall in the last 24 hours:||3 inches|
|Total snow depth:||NA inches|
Area Forecast Discussion
National Weather Service Boise ID
304 AM MST Wed Jan 22 2020
.SHORT TERM...Today through Saturday...Weak cold front brought
rain and snow showers and slight cooling to the area Tuesday
afternoon and evening. The associated upper trough was passing
through our CWA early this morning. The next Pacific warm front
is already spreading clouds inland over western Oregon. Chance
of rain and mountain snow will spread across eastern Oregon later
this morning through afternoon, and western Idaho tonight, mainly
north of the Snake Basin. Light pcpn will continue in
northern-most areas Thursday while southern areas dry out. By
then our CWA will be in the warm sector south of the warm front
and temperatures will rise even more with highs near 50 in the
lower southwestern Idaho valleys, 40s in other valleys, and 30s
only in the mountains. The following cold front will bring the
heaviest pcpn of the week Friday morning, with accumulating snow
only above 5000 feet. Friday night will be drier and only
slightly cooler. The next Pacific warm front and more pcpn will
come in Saturday.
.LONG TERM...Saturday night through Wednesday...Southwest flow
aloft originating from the subtropics will allow for mild
conditions to continue on Sunday ahead of an approaching system.
High temperatures in the Treasure Valley on Sunday will surpass
50 degrees, with the entire region roughly 10 degrees above normal.
By Monday, an upper trough will swing across the Intermountain
West and spread precipitation across the region. Snow levels will
stay 4000-5000 ft MSL until Tuesday where they fall to the valley
floors. Temperatures will decrease nearly 5 degrees for the
duration of this system, though conditions will still remain
several degrees warmer than normal. The trough and associated
precip move off to the east by Wednesday, though the pattern
beyond looks to stay unsettled.
.AVIATION...Areas of fog and low stratus causing MVFR to LIFR
conditions. Mountains obscured. Clouds filling in across the
region from the SW will cause conditions to improve to mostly
VFR/MVFR through the morning. Another round of showers will
enter the region from the W this afternoon, spreading across
each terminal through the evening. Snow levels: 4000-5000 ft
MSL. Surface winds: mostly variable 10 kts or less. Winds
aloft near 10k ft MSL: W 20-30 kts.
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.