Glacier National Park Avalanche Forecast

Issued: Jan 5th, 2021 8:15AM

Mon Jan 4th Current Conditions
Alpine Considerable Treeline Considerable Below Treeline Considerable
Tue Jan 5th 2 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Considerable
Wed Jan 6th 3 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Moderate

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Loose Dry.

A reactive storm slab at and below treeline was triggered by multiple parties yesterday in Puff Daddy, Napoleon Spur, and McGill.

Choose conservative, well-supported runs today and avoid getting pushed into a terrain trap.

Summary

Weather Forecast

Cloudy with flurries the next couple of days, then a high pressure ridge will clear things out by Thursday

Today: cloudy with sunny periods, trace snowfall, Alpine high -8*C, light/mod SW winds

Tonight: increasing cloud, 4cm, alpine high -8*C, mod S winds

Wed: flurries, 5-10cm, alpine high -7*C, gusty mod SW winds

Thurs: cloud with sun, light winds

Snowpack Summary

75cm of snowfall over the last 3 days was accompanied by strong to extreme winds from the SW. A surface hoar layer, buried Dec 26, is preserved in sheltered areas at and below treeline, down 70+cm. The Dec 13 surface hoar can still be found down 120cm and the Dec 7 crust/facet/surface hoar (aspect/elevation dependent) layer is down 135+cm.

Avalanche Summary

Overnight natural activity saw several sz 3's off Mt's Tupper and Macdonald.

Multiple MIN reports indicated people were able to trigger soft slabs, 30-70cm deep, at and below treeline to sz 2 yesterday.

Large avalanches to sz 4 were triggered by artillery control Saturday night, which ran to valley bottom and buried the highway.

Confidence

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3.5

Heavy snowfall over the weekend, accompanied by strong-extreme SW wind, has built thick storm slabs in all open terrain.

A Dec 26 surface hoar layer persists below this slab, 50-70cm deep, in sheltered areas at treeline and below.

  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • The new snow will require several days to settle and stabilize.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely

Expected Size

2 - 4

Avalanche activity this weekend shows that large triggers (such as cornices and storm slabs) could still cause very large avalanches on these layers.

  • Be wary of large slopes that did not previously avalanche.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects:

All aspects.

Elevations:

All elevations.

Loose Dry

An icon showing Loose Dry

Likelihood

Likely

Expected Size

1 - 2

Plenty of loose snow exists in sheltered locations at and below treeline. Skier triggered sluffs have the potential to collect significant mass and bury a person in a terrain trap. Sluff management is essential today.

Aspects:

All aspects.

Elevations:

Treeline, Below Treeline.

Valid until: Jan 6th, 2021 8:00AM