THIS AVALANCHE ADVISORY EXPIRED ON March 25, 2018 @ 6:58 am
Avalanche Advisory published on March 24, 2018 @ 6:58 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Hazard is MODERATE today throughout the West Central Mountains.  Cooling temperatures following Thursday's rainy warmup have started to stabilize and refreeze the snowpack. The upper elevations have already seen a significant refreeze while middle and lower elevation slopes are still in the process of a solid refreeze.  Shallow, stiff wind slabs may be encountered on upper elevation, wind exposed 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: Loose Wet
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It is still possible to trigger loose/wet avalanches today.  If the sun pops out, the likelihood of natural or human triggered wet slides will rise, especially on steeper, rocky slopes that are tilted toward the sun. Loose/wet avalanches tend to follow the sun throughout the day during springlike conditions;  E/SE slopes will see the sun early in the morning, potential for natural avalanches will begin here and continue throughout the day to S then SW slopes.  Lower elevation slopes are going to take a few more cold nights to completely refreeze as temperatures were still hovering near freezing early this morning.

Here is a photo of an East facing slope near Fisher Saddle that shows examples of classic loose/wet slides that occurred between Thursday and Friday.   Even small wet slides pack a big punch, once you get your skis or sled stuck in the debris, it is very difficult to get out.  If you are in steeper terrain and you are not riding on a firm crust, be aware of the terrain below you.  Don't let one of these small slides drag you trough rocky,  or treed areas or even worse over cliffs or into gullies.

 

Avalanche Problem 2: Wind Slab
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S, SW and W winds have been gusting with the unstable atmosphere for the last 48 hours.  Stiff wind slab or wind board has been forming in the dense snow near the ridgelines and on exposed, upper elevation terrain.  With little new snow accumulation to accompany the wind, these are still likely to be shallow but they will be dense or even firm and may crack or propagate under your skis or sled. If you notice a change in the hardness of the snow you are riding in or the snow feels hollow or drumlike, you are on a hard wind slab.

recent observations

Small, natural loose/wet avalanches were widespread throughout the last 48 hours on many steep slopes.  Cooler temperatures tonight should bring about a deeper refreeze and continue to solidify the snowpack. Yesterday saw several rounds of snow that was heavy at times but didn't accumulate much.  The upper elevations will likely have a thin dusting of new snow on the hardening crust today.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 18 deg. F.
Max. temperature in the last 24 hours: 22 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 31 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 57 inches
weather

SHORT TERM...Today through Sunday...An upper level trough sitting
off the Pacific Coast will begin its slow swing into the region
today, bringing still more precipitation to the region this
weekend. Precipitation will fall as snow across most elevations,
with a mix along the Snake River Plain. Today`s focus of
precipitation will fall across the west central Idaho mountains
and along the Nevada border; however, as the trough axis moves
across the region Sunday, most areas will see a flake or two. With
a cold pool aloft and an unstable environment associated with the
upper level trough axis, a slight chance for afternoon
thunderstorms Sunday cannot be ruled out and has been added to
the forecast. Snow amounts are expected to be around 1 to 3 inches
across most locations below 6000 feet this weekend, except along
the I-84 corridor where little to no accumulation is expected.
Above 6000 feet, total accumulation will generally be 3-5 inches.
Temperatures will be about 10 degrees below normal through the
weekend.

LONG TERM...Sunday night through Saturday...Northwest flow will
follow the trough as it exits early in the week. This will
continue the chance of showers across the mountains while lower
elevations dry out. The best chance for precipitation comes late
Tue/Wed as a weak trough passes north of the area. Snow levels
will rise from around 3k feet on Monday to around 6k feet by
Wednesday. While moisture in the flow increases for Tue/Wed, lift
is mainly orographic and precipitation amounts will be light.
Models in good agreement on an upper ridge building into the
western US later in the week, bringing drier and warmer conditions
Thur/Fri. Temperatures warm from around 10 degrees below normal
on Monday to 5 degrees above average by Thursday. The weekend
looks cooler and possibly wetter, as energy from the Gulf of
Alaska approaches the Pac NW.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers likely, mainly before noon. Mostly cloudy, with a high near 34. Southwest wind around 14 mph. Chance of precipitation is 60%. Total daytime snow accumulation of around an inch possible. A 20 percent chance of snow showers after midnight. Partly cloudy, with a low around 18. South southwest wind 5 to 7 mph becoming calm in the evening. A 40 percent chance of snow showers. Some thunder is also possible. Partly sunny, with a high near 34. Calm wind becoming west 5 to 7 mph in the afternoon. New snow accumulation of less than one inch possible.
Temperatures: 34 deg. F. 18 deg. F. 34 deg. F.
Wind direction: SW SSW W
Wind speed: 14 5-7 5-7
Expected snowfall: 1 in. 0 in. Trace in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers, mainly before noon. High near 21. Wind chill values between zero and 5. Breezy, with a southwest wind 18 to 24 mph. Chance of precipitation is 90%. Total daytime snow accumulation of 1 to 3 inches possible. A 20 percent chance of snow showers after midnight. Partly cloudy, with a low around 13. South southwest wind 6 to 13 mph. Snow showers likely, mainly after noon. Some thunder is also possible. Partly sunny, with a high near 22. West southwest wind 5 to 8 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 21 deg. F. 13 deg. F. 22 deg. F.
Wind direction: SW SW W/SW
Wind speed: 18-24 6-13 5-8
Expected snowfall: 1-3 in. 0 in. 1-3 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.