The wind slab crowns that we have seen over the last couple days in the new snow have been mostly on North, and some Eastern aspects. Given the variability in direction of wind that we have seen, I would not rule out other aspects. Look for signs like shooting cracks, hollow sounding snow, or pillows to indicate wind slab location. Wind slabs are likely sitting on a variety of old snow surfaces including crusts and faceted snow.
Each day we have seen new small loose wet point releases on aspects under direct sunlight. Late afternoons have softened the snow enough to sink in over your boots which indicates potential to get a good amount of snow moving. Be cautious on and under slopes getting heated by the Sun.
If you see or trigger avalanches, please take the time to snap a picture, note key features of the slide as well as an estimate of aspect and elevation. Your observations help us paint a better picture of what is happening across the PAC advisory area. You can submit an avalanche or snowpack observation at: http://payetteavalanche.org/observations click on the menu link for observations then either avalanche or snowpack. It is SUPER easy, takes 5 minutes and can be as detailed or limited as you want.
Out North of Granite Mountain Yesterday, we had mostly cloudy skies as the current storm moved in. Light flurries, and occasional sunshine and warmth was the theme. Northern aspects are still holding good soft snow, but if you veer off of due North you may encounter a crust on the surface that the Sun has formed. Our test pit at 7700 feet on a NNW aspect revealed a layer of facets under the new snow, about 1-1.5 feet, that was noticeable in a mit pit earlier, and came out with a hard compression test result CT28, and no propigation on an extended column. We did notice some small old crowns R1D1, in the new snow under steep north facing rocks with faint debris piles that likely failed during the storm or just after when North winds came in.
Soft snow on a North aspect.
Solar aspects heated up, and produced loose wet point releases near rocks, and decent snowmobiling. Ice scratchers on snowmobiles in the morning were challenged to keep our Snowmobiles cool, but soft snow exists in shady areas and areas without tracks you can break through some crusts down to the soft snow.
We stopped by our Granite weather station and probed to see how much snow is there as the depth sensor is slated for replacement. We found 228 cm, or 7 and a half feet of snow.
|0600 temperature:||23 deg. F.|
|Max. temperature in the last 24 hours:||36 deg. F.|
|Average wind direction during the last 24 hours:||N|
|Average wind speed during the last 24 hours:||5 mph|
|Maximum wind gust in the last 24 hours:||14 mph|
|New snowfall in the last 24 hours:||NA inches|
|Total snow depth:||90 inches|
Area Forecast Discussion
National Weather Service Boise ID
237 AM MDT Wed Mar 18 2020
.SHORT TERM...Today through Friday night...Areas of clear skies
this morning could allow for patchy fog to develop in some valley
locations, which will end by late morning. Otherwise, an upper
low centered in Nevada will continue to provide our area with
scattered showers today, along with isolated afternoon
thunderstorms near the Nevada border. The upper low will move
south and away from the area by Thursday as weak high pressure
aloft builds in from the Pacific Northwest. This will bring drier
conditions through Friday, with the exception of a slight chance
of afternoon showers near the ID/NV border and in central Idaho.
Winds will be light, except gusty winds will accompany the
thunderstorms. Temperatures will be slightly below normal today,
and near to slightly above normal Thursday and Friday.
.LONG TERM...Saturday through Wednesday...Dry northwesterly flow
to start our extended forecast period ahead of the next system.
Models are still struggling to come to an agreement on how/when
the next system drops into the region, but do show an overall
wetter pattern returning by Monday afternoon. This low pressure
system will skirt just west of our area dropping to our southwest
by the end of the period. Expect an increase in shower activity
Monday evening onward through the end of the period, especially
for higher elevations. Temperatures remain close to normal.
.AVIATION...Isolated showers will continue through the night and
into Wednesday afternoon pushing in from the south. MVFR/IFR
conditions expected within shower activity. Areas of fog and low
stratus can be expected for lower valleys creating MVFR to LIFR
conditions. Surface winds, light and variable. Winds aloft to 10k
feet MSL, south to southeast 20-25kts.
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.