Northwest Mountains

Warm temperatures and sunny skies bring the return of wet avalanche problems in addition to the nagging slab avalanche concerns.  On the north half of the compass, the threat of you triggering a large slab avalanche lingers though it has been about a week since the last loading period and last triggered avalanches (Owen, Cement Creek).  The recent strong northerly winds formed stiff slabs on isolated, leeward features that may remain sensitive today; you can identify these by a smooth-looking appearance.  And finally, warm temperatures and sunny skies will soften and wet surfaces on the south half of the compass creating loose avalanche concerns.  Steer clear of recently wind-loaded terrain on all aspects and manage surface wetness on sunny slopes during the heat of the day.

Warm, spring weather brings a mix of avalanche problems for you to manage today.  On the north half of the compass, you need to consider the possibility of triggering a Persistent Slab that could break several feet deep, on leeward features you can find isolated stiff slabs that recently formed from strong northerly winds, and on sunny slopes, Wet Loose avalanche concerns will develop throughout the day.

Persistent Slab:  Due to the potentially large and dangerous size, and the inherent, unpredictable behavior, this is your greatest hazard today.  Slabs have the potential to break several feet thick on weak layers buried in mid-February.  We are now more than 10 days out since our last notable loading event ended, and the likelihood of triggering a persistent slab is decreasing.  In the Northwest Mountains, we've lowered the likelihood of persistent slabs to "unlikely".  In general, the snowpack is deeper and weak layers are improving faster in the snow-favored zone.  There are always exceptions, especially in wind-affected alpine terrain. Given the potential size and variability near and above treeline, our travel advice remains consistent with Moderate danger.   Near the boundary of our two zones, and in the Southeast Mountains, collapses, shooting cracks, and unstable pit results have continued relentlessly since our weak layers were first buried.  Slabs are a bit thinner, weak layers are weaker, and human triggering remains possible on slopes that didn't already avalanche during the late February cycle.

Wind Slab:  Strong northerly winds blew for three days (Monday through Wednesday) transporting snow onto leeward features (most commonly on southerly aspects, but can also be hiding on cross-loaded windward terrain).  On Tuesday, a forecaster triggered a small Wind Slab in a northwest-facing chute and a snowboarder nearly triggered a Wind Slab on the south side of Teocalli.  On Wednesday, I found a drifted southerly feature on Baldy that produced propagating results while isolating the column in a snow pit.  You can identify the recent drifts with a smooth appearance and a stiff, supportive feel.  Your best tactic will be to simply steer around terrain features that you suspect have a freshly, drifted slab regardless of aspect.  You may find Wind Slabs in unusual places due to wind speeds hitting 60+ miles per hour. 

Wet Loose:  Today marks the first day in a warming period.  Expect southerly-facing terrain to become wet and produce human-triggered loose avalanches as conditions warm.  There is some uncertainty about the spread of Wet Loose avalanches on shoulder aspects facing east and west, so take the time to assess surface wetting on sunny slopes at all elevations.  Given a solid overnight freeze, Wet Loose avalanches are expected to remain relatively small but could grow big enough to knock you down and take you for a ride.  Sinking to your boot tops is a good sign that you are too late and should move to a cooler aspect where conditions have not warmed as much.  Expect wet avalanche concerns to grow in size and distribution over the next few days as the weather becomes warmer and overnight freezes weaken.