Snowpack Summary published on March 17, 2017 @ 4:25 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Mountian weather forecasts are calling for another warm and wet system to impact the area begining Friday afternoon.  This system is expected to bring snow to the mountains above 5,000' this evening.  This snow will fall on a firm rain crust.  Moving into Saturday the snow line is likely to rise to 7,000'.  This new loose snow sitting on a rain crust will create ideal conditions for loose-wet avalanches as temperatures rise and snowfall transitions to rain this weekend.

BOTTOM LINE: If the weather forecast holds true then we will likely see widespread loose-wet snow avalanches in steep terrain at elevations above 5,000' this weekend.

Avalanche Character 2: Wet Slab
Wet Slab avalanches occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoid avalanche terrain when you see pinwheels, roller balls, loose wet avalanches, or during rain-on-snow events.

This problem will be most likely to cause problems in the Purcell Range of the Yaak where deep weak layers persist within the snowpack that may become more reactive as the warm temperatures and rain reduce the strength and increase the weight of the snowpack.

BOTTOM LINE: It would be prudent to approach the steep terrain of the Purcell Range with caution on warm, rainy days as these weak layers will be highly unpredictable until the snow pack has consolidated with mutliple melt-freeze cycles.

Snowpack Discussion

Spring is coming!  If you are like me and you are still excited to wander into the mountains and look for snow then we need to be following the weather.  The avalanche stability will be dictated more by rapid temperature changes and sun than by tricky layers in the snow pack.  Pay attention to the weather forecast and the obvious signs of instability caused by rapid warming.

For those riding near the state line get some additional info on conditions, check out the Panhandle forecast by clicking the link below!

recent observations

On March 16th we travelled to Smith Mountain via Callahan Creeek.  We observed some signs of small, loose wet slides that had released during the warm, rainy spell that came through the area on Tuesday and Wednesday.  Temperatures were just below freezing which was locking the upper snowpack back together. (i.e.-crusty!) Snowpit tests revealed some weak layers but showed low likelihood of propagation.

weather summary

Backcountry Forecast from NWS Missoula issued:
400 AM MDT Fri Mar 17 2017

DISCUSSION: Warmer temperatures arrive with high pressure today.
The next weather system is approaching and cloud cover will lower
and precipitation to begin in Idaho and northwest Montana
beginning this afternoon and evening. This is another warm and
very wet weather system with rain totals 1.00"-1.50" to be common
in north central Idaho and northwest Montana by late Saturday.
West central Montana will have lesser amounts. The cold front has
the potential to be very strong on Saturday with high winds,
thunderstorms, and quickly dropping snow levels during the
afternoon and evening.

--------------------------- 5000-7000 FT ----------------------------
                               Today          Tonight      Sat     
Cloud Cover            80%            100%          100%    
Hi/Lo Temps           35 to 43     30 to 36      41 to 47
Winds(mph)             S  8            S 13G28      SW 22G45
Precip Chc               70              100             100     
Precip Type             snow          sno/rain      showers 
Liquid Amt              0.06            0.61            0.84        
Snow Amt(in)          0-1              3-7             0       
Snow Level             3000           5000          7000   


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 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.