Flathead Range & Glacier NP

You can trigger avalanches where the wind has drifted or stiffened the snow surface. A small slide could initiate a much larger avalanche on a buried weak layer. Sustained sunshine may start loose sluffs in the surface snow. Choose terrain sheltered from the wind or lower-angle slopes for a safer, higher-quality experience.

Southwest winds peaked Thursday as moderate to strong sustained winds and blowing snow were observed at all elevations. Gusts reached extreme or gale force throughout the day. Observers noted fresh wind slab and cornice development reactive to a rider's weight. Winds and blowing snow tapered a bit Friday, with the WMR ski patrol noting stiffer slabs less reactive to ski cutting. At the same time, explosive mitigation produced effective results only in the most favored locations for wind loading. Snow redeveloped overnight, with mid-elevation stations picking up 2-6 inches. 48-hour snow totals are generally in the 6-12 inch range, with the southern Whitefish Range and the Tunnel Ridge station favored.

This morning winds are shifting to the south and eventually will shift to the southeast by mid-day. Fresh slabs may develop on the west side of the compass, with thickening slabs on typical leeward aspects (NW-NE-SE). Arctic air creeps over the Continental Divide tonight, bringing unseasonably cold air with northeast winds. The pool of cold air does not look as deep as experienced during the late-February cold snap. This should help to keep the temperatures from dropping to dangerously cold readings. We expect winds to transport loose, dry snow onto atypical aspects overnight. 

The last report of a Persistent Slab avalanche was 11 days ago during the Atmospheric River event of February 20 and 21. In the Swan Range, the buried surface, hoar, and facets are generally found at depths greater than three feet or deeper than the effect of a rider or their snowmachine. This weak layer has been identified in the northern Whitefish Range, but observations have not confirmed much activity since forming in mid-January. Areas in the southern Whitefish Range do not harbor this layer. We are more concerned about this layer in the Flathead Range and southern Glacier Park, where it is closer to the surface and now capped with a thick slab. This is why we list the likelihood of triggering in this range as POSSIBLE and UNLIKELY elsewhere.

Despite today's cool temperatures, sustained March sunshine may warm the recent snow and develop loose snow instabilities. Snow falling from tree branches or peeling off rock faces could initiate loose dry slides in the surface snow. In sheltered locations, riders may be able to trigger sluffs on steep slopes. Expect to manage your sluff and limit time spent in long-running gullies or above terrain traps where the snow can pile up deep.

FAC would like to thank Ted Steiner and Adam Clark from the BNSF snow safety team for help in replacing the temperature and relative humidity sensor at the Aeneas Ridge weather station. This sensor has been out of service all season, and FAC staff are delighted to have this data to help us forecast this spring's freeze/thaw and wet snow problem in the Swan Range. They also fixed issues with the wind anemometer. 

Avalanche Encyclopedia: The National Avalanche Center has issued a new and updated encyclopedia containing 257 avalanche-related terms, a new graphic design, a new hierarchical term structure and navigation, and a new user interface. The US Forest Service funded the project. The writing and content were produced by Zach Guy, former Director of the FAC. You can find it here.

State of the Snowpack and Fireside Chats. Join us at 6 pm on March 9 for a virtual evening combining two of our popular community ed workshops. New this season, State of the Snowpack is a presentation from FAC on recent weather and avalanches to help you digest the forecast and plan your weekend. Fireside Chats are an intimate, conversational forum for open dialogue about human and avalanche factors. With skier/psychologist Dr. Sara Boilen as our facilitator, we dig into the tough decisions, tricky snow, and lessons learned from local near misses. No registration is needed; click here for a Zoom invite.