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.
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.
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!
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.
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.