Kootenai National Forest Avalanche Advisory – 3/18/2014

The avalanche information for the Kootenai National Forest is provided by Kootenai National Forest personnel. The Flathead Avalanche Center hosts this information on its website for the Kootenai National Forest.

THIS ADVISORY HAS EXPIRED

Issued: March 18, 2014 at 7:00 a.m. by Jon Jeresek
Expires: 11:59 p.m. of issue date

This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory for the Kootenai National Forest area will be Friday, March 21, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Friday morning (March 14th) advisory, heavy amounts of snow (snow water equivalent 1.1- 4.9 inches) accumulated at all SNOTEL sites in the Kooteani advisory area (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman Cr).  Winds Friday through Monday were from the southwest at variable speeds with a bit of snow transport of new snow.  Temperatures at all sites have been mostly above freezing except for a few brief freezing periods. There is soft new snow available for wind transport within our advisory area.

FORECAST:  Mostly cloudy skies Tuesday through Thursday.  All daytime temperatures are forecasted to be near freezing in the low 30s F, with night time temperatures in the mid 20s F.  Winds will be out of the southwest at 8 – 13 mph Tuesday through Thursday. Chance of snow is 20-80% through Thursday with accumulations of 8” – 13” forecasted.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Poorman Basin in the East Cabinets located 17 air miles south of Libby on March 17th.  Total snow depth is 95-100 inches on a southeast aspect at 5500 feet. Four inches of new snow sits atop a 10 inch rain saturated layer from Sunday night.  Below this rain layer is wet snow 12 inches thick from last Friday. The upper 14 inches of the snowpack releases easily using the compression stress test.  The mid pack hard slabs release cleanly with moderate to hard force.  Below these snow layers is the old snow melt-freeze crust.  The base of the snowpack shows depth hoar development as a result of the severe temperature gradients during the first week of February.  Currently, there are no significant temperature gradients in the snowpack to drive change processes. 

D2/R3 rain triggered debris from 03/17/2014.

D2/R3 rain triggered debris from 03/17/2014.


03/10/2014 debris damming Poorman Creek. Taken: 3/17/2014.

03/10/2014 debris damming Poorman Creek. Taken: 3/17/2014.


D4/R4 rain triggered wet slab from 03/06/2014 . Taken: 3/17/2014.

D4/R4 rain triggered wet slab from 03/06/2014 . Taken: 3/17/2014.


Snomobile parked near 03/10/2014 rain triggered wet slab debris. Taken: 3/17/2014.

Snomobile parked near 03/10/2014 rain triggered wet slab debris. Taken: 3/17/2014.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  


 

  SNOWPACK DISCUSSION

Avalanche Problem #1

 Wet SlabWe have experienced exceptional rain on snow loading through 03/17/2014.  Rain triggered slab releases were common 03/06/2014 and 03/10/2014, and again yesterday (3/17/).  However, the natural releases yesterday appear to be “clean up” releases that ran as smaller (D2/R3) events.  Back country travel during or immediately after significant rain on snow events is NOT recommended.

 

 

 


 

 Avalanche Problem #2 

Glide

With abundant rainfall on snow since 03/04/2014, steep snow packs over bedrock or smooth slopes have developed cracks and full depth glide cracks exist. These locations should be identified and avoided.

 

 

 

 


TREND:  New snow is forecasted Tuesday morning through Thursday with 8 – 13 inches expected.  We expect wind transport (SW 8 -13 mph) of new snow.  Temperatures are forecasted to be near freezing daytime in the low 30s, and night time in the mid 20s through Thursday.  


  BOTTOM LINE

The avalanche hazard in the West Cabinets, East Cabinets and Purcell Range is CONSIDERABLE.  This means that dangerous avalanche conditions exist on many terrain features, especially during the height of day time heating.  Natural avalanches are possible, and human triggered avalanches are likely.  Careful snowpack evaluation, cautious route finding, and conservative decision making are essential.

SPECIAL NOTE:  Significant rain on snow is the most destructive agent to snowpack stability.  If it has rained just before or during your back country trip, have a safe exit route in your travel plans and use it!  Rain triggered wet slabs are hugely destructive and have low survivability potential.


 DISCLAIMER

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.