Avalanche Advisory – 3/26/2014

THIS ADVISORY HAS EXPIRED.

Issued: March 26, 2014 at 7:00 a.m.
Valid Until: 11:59 p.m. of issue date

Good morning! This is Todd Hannan with the Flathead Avalanche Center avalanche advisory for Wednesday, March 26, 2014. This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory will be Saturday, March 29, 2014.


MOUNTAIN WEATHER

WeatherGraphicOver the past 48 hours a ridge of high pressure over the region has maintained dry conditions with warm daytime temperatures and light winds. Yesterday, several mountain locations had temperatures in the 50s, Flattop Mountain SNOTEL recorded a high temperature of 52°F. Overnight temperatures were slow to dip back below freezing and a few areas near the divide picked up a small amount of snow last night (up to 2 inches). Currently, remote weather stations and SNOTEL sites are reading 25 to 33 °F with winds out of the southwest at 5-10 mph and gusts to 20 mph. Today light snow showers should continue in the area with gradually lowering snow levels and winds will be 5-15 mph out of the southwest. Showery conditions look to persist through Friday with precipitation becoming more steady Friday afternoon.

 


RECENT OBSERVATIONS

RecentObservationsGraphicYesterday was a beautiful day to ride into Kimmerly Basin in the Whitefish Range. We skied out Skookoleel Ridge in the morning and found unconsolidated surface snow on shaded aspects and a supportable melt-freeze crust on sunny aspects. It did not take long for the sun to penetrate the crust formed in the previous night, by noon our skis began to sink into the snow surface on sunny slopes. We dug snow pits on south, west, and north aspects (profiles). Our most concerning find was on a south aspect in an area of relatively shallow snow (205cm). The snow on the ground was weak and faceted and our entire column failed upon isolation (ECTPV). The good news is that the weak snow near the ground in this area was bridged by a nearly 20 cm(8 inch) thick melt-freeze crust making it difficult to trigger. Though, this still serves as a reminder that these instabilities continue to exist in our snowpack and ARE buried shallower in some areas with less force required to trigger an avalanche (Photo 1,2). On shaded aspects we observed small surface hoar developing and weak snow near the surface that could become a future issue with new snow on top.  While riding out of Kimmerly Basin in the afternoon we observed relatively small loose, wet avalanche activity on sun exposed slopes (photo).

BNSF avalanche safety was in the John F Stevens Canyon yesterday and found several layers of concern that were deeper in the snowpack, stability testing produced variable results on these layers (observation).

On Sunday skiers on Peak 6996 in the John F Stevens Canyon found a small layer of weak snow 70 cm from the surface that failed in compression tests with hard force(observation).

 

Large grained depth hoar found near the ground. Skookoleel Creek, Whitefish Range. 3/25/2014

Large grained depth hoar found near the ground. Skookoleel Creek, Whitefish Range. 3/25/2014


Entire column failure upon isolating the back of the column. Skookoleel Creek, Whitefish Range. 3/25/2014

Entire column failure upon isolating the back of the column. Skookoleel Creek, Whitefish Range. 3/25/2014


Loose, wet avalanche in Kimmerly Basin. Whitefish Range 3/25/2014

Loose, wet avalanche in Kimmerly Basin. Whitefish Range 3/25/2014


Loose, wet avalanche in Kimmerly Basin. Whitefish Range 3/25/2014

Loose, wet avalanche in Kimmerly Basin. Whitefish Range 3/25/2014

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


SNOWPACK DISCUSSION

Avalanche Problem #1

Deep SlabThough deeply buried and difficult to trigger, the late January/early February crust/facet layer in addition to weak, faceted snow near the ground still lurks in the snowpack. The best place to trigger an avalanche on these layers is shallow, rocky areas so avoid this type of terrain. The rain event that provided the trigger for that large avalanche cycle in early March formed a thick rain crust that now sits about 2-3 feet from the surface. This layer has shown instability in some areas with recent stability tests. The chances of triggering an avalanche on these layers may be low, but the consequences are high. It remains important to do site specific evaluation of persistent slab in the areas you are travelling and remember that tracks (even lots of tracks) do not mean stability. Given the uncertainty of these deep slabs, it is best to avoid slopes where these layers exist or just avoid steep slopes altogether. Additionally, large cornices tower over many slopes in the area and their strength will be tested through the spring with increasing direct sun and warming temperatures. The large amount of force exerted by a falling cornice can trigger these deep instabilities. It will become increasingly important to be aware of cornices when travelling in the backcountry. As usual, give them a wide margin when above them and avoid areas below them.

 


 

Spring can bring a mixed bag of weather and snow conditions. Mountain temperatures remain near the freezing mark this morning and a small amount of precipitation is in the forecast. It is important to pay attention to rapidly changing conditions as weather can greatly affect snow and avalanche conditions this time of year. Pay particular attention to rain falling on the snow if temperatures climb higher than expected.

 


BOTTOM LINE

For today, the overall avalanche hazard is MODERATE. This means that human triggered avalanches are possible, particularly on steep slopes and areas of shallow snow where deeper instabilities exist in the snowpack. It remains important to evaluate snowpack and terrain carefully in the specific areas that you are travelling in.

Moderate_2

 


Note: The accuracy of the avalanche advisory becomes much more robust when we have more information. Thus, observations from all of you are extremely valuable to us. Even it is just a simple email saying “Hey, we found good riding in Mountain Range X, and observed no signs of instability or recent avalanches”. This type of information is just as important as observations of avalanches. The observations need not be formal, and can remain anonymous. Don’t’ worry, we won’t give away your secret riding/skiing spot either. Call us at 406.261.9873 or email us at fac.admin@flatheadavalanche.org. Thanks for your help.


See recent snow profiles as well as snow profiles from the entire season here.

Check out an interesting new research project that you can participate in about winter backcountry riding/snowmobiling and decision making from the Snow and Avalanche Lab at MSU. Details here.


DISCLAIMER

DisclaimerGraphic

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 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.