Avalanche Forecast

Sunshine and moderating temperatures should be the story on Thursday. However, cool easterly winds should locally keep rising freezing levels in check near the Passes and along ridges of the central and southern Cascades affected by east winds.

Still, mid-March sunshine will affect solar slopes by increasing the likelihood of loose wet avalanches on steeper solar aspects by quickly breaking down sun or melt-freeze crusts. While most loose wet avalanches should be small, they will have the ability to entrain recent moist snow in specific terrain. Recently formed cornices have grown large and should become more sensitive with warming and sunshine. You can mitigate the loose wet and cornice risk by being aware of the terrain your connected with and by recognizing the rapidly increasing hazard in locations that warm quickly.

Northwest winds on Wednesday likely continued to build wind slab on lee aspects in the upper elevations of the above treeline band. Wind slab will mostly likely be found on N-SE facing slopes. Firm wind transported snow and snowpack cracking can be good signs of wind slab instabilities. Treat wind-loaded slopes in higher terrain with caution Thursday.

Weather and Snowpack

Storms have moved across the Northwest at a nearly daily frequency the past few weeks with fluctuating but generally moderate snow levels. Two deep surface low-pressure systems moved across the Olympic Peninsula last week with the first passing last Thursday, March 10th and the next on Sunday, March 13th. These systems caused very stormy weather.  

Cool and showery weather Monday and Tuesday with continuing moderate westerly winds deposited additional snow at lower snow levels. Storm totals from Thursday, March 10th through Tuesday morning have been between 2 - 3.5 feet!

Daytime warming and settlement have allowed recent storm-related weak layers to quickly settle and stabilize. The quickly stabilizing storm slabs have been verified by many field observers and practitioners over the past few days. These recent storms have also built large cornices along ridges in many areas.

The solid mid and lower snowpack along the west slopes remains a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

The Mt. Baker pro-patrol reported yet another glide avalanche to ground (5-6' deep!) on a steep rockface around 3500 feet in the below treeline band off of Shuskan Arm on Tuesday. Powerful glide avalanches remain possible in isolated terrain features such as on steep slopes with smooth bed surfaces and especially where the slabs are unsupported from below. These avalanches are not predictable in the sense that they are not tied to short term warming or rain events. Specifically in the Mt. Baker backcountry, we want to highlight the low likelihood-high consequence of this sporadic but ongoing avalanche hazard during this wet winter.  

NWAC observer, Lee Lazzara  was in the Mt Baker backcountry Tuesday near Table Mt and Mt Herman. The main takeaway was that wind slabs were still sensitive to ski release on steep open slopes, with a skier triggering a size D1 wind slab on a steep NE facing slope. The mid-March solar radiation was quickly settling storm slab instabilities and causing 5-10 cm on wet surface snow on solar aspects, producing several small loose-wet slides.  

Pro-observer Dallas Glass was in the Kendall Peak area of Snoqualmie Pass Wednesday. He found that while density differences persisted in the layering of recent storm snow, propagation was unlikely and that overall instabilities had settled out within the 60 cm of storm snow over the 3/12 rain crust. As the sun poked out mid-day Wednesday, generally small loose wet avalanches were observed in steep terrain of Kendall Peak on S-SW aspects.