Likelihood ?CertainVery LikelyLikelyPossible
Size ?HistoricVery LargeLarge
There are still some "persistent weak layers" buried within the snowpack. These layers are still worth paying attention to in steep terrain above 6,500', particularly in the thinner snowpack of the Purcell Range. Use caution and check out the snowpack before committing to steep terrain above tree-line, and as always practice safe travel habits when playing on or near steep terrain. As I mentioned, this problem fits into a low-likelihood/high consequence situation.
On December 27th we travelled back into the Cabinets with the goal of gaining some altitude and thouroughly checking out the potential for any lurking wind slabs at upper elevations on leeward terrain. The tour verifiied that the recent wind slabs have stabilized and are unlikely to cause a problem at this time. We encountered generally stable conditions on all aspects. There are a lot of thin, hollow spots and sugary snow near wind-swept ridgelines and on south-westerly aspects that could present a problem moving forward if the area comes under north-easterly winds. This is always a possible scenario during cold front passages. We dug into the snow on a southerly aspect to check out the snow on the thin side of the mountain where we observed some weakness (old graupel and 2 crust layers). Neither of these layes proved to be reactive or show the potential to propagate at this time.
Moving forward into the weekend there is potential that snow conditions will change as the National Weather Service is hinting at a storm moving into Western Montana late Saturday and Sunday. Looking at the forecast it seems possible that the brunt of this storm may miss the area. Continue to keep an eye on the forecast this weekend and give steep slopes some time to settle if we recieve another dose of heavy snow in the mountains.
Check out the short video below to see the snowpack in the East Cabinets, 6.5' at this location on Christmas Eve. Game on!
Backcountry Forecast from NWS Missoula issued:
1220 AM MST Thu Dec 27 2018
DISCUSSION: Lingering snow showers over the terrain of west-
central Montana, including the Mission Mountains are expected to
finally diminish by mid morning. Our next weather system will
begin to spread light to moderate snow over western Montana late
tonight and persist through the day tomorrow. No significant
accumulations are expected with this disturbance. The next
potential significant weather system is possible by the end of the
weekend. Confidence on snowlevels remain uncertain due to
disagreements between Models, though moderate to heavy snow for
the higher terrain is likely.
--------------------------- 5000-7000 FT ----------------------------
Tonight Fri Fri Night Sat
Cloud Cover 35% 75% 90% 95%
Hi/Lo Temps 7 to 16 17 to 23 14 to 20 27 to 32
Winds(mph) NW 8G22 SW 9G23 SW 14G31 SW 18G39
Precip Chc 0 30 60 80
Precip Type snow snow snow snow
Liquid Amt 0.00 0.01 0.03 0.09
Snow Ratio(SLR) 19:1 19:1 18:1 14:1
Snow Amt(in) 0 0 0 1
Snow Level 0 0 0 1000
Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit. For a recorded version of the Avalanche Advisory call (208)765-7323.
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