A MODERATE avalanche danger exists on steep west through north through east facing slopes above about 9,000 feet, where it’s possible to trigger a 1–2 foot thick slab failing on old October–November faceted snow (persistent weak layer).
As the day warms, the danger for wet avalanches will quickly rise to MODERATE on many slopes. Wet loose avalanches and the possibility of wet slabs will remain a possibility through the weekend.
Old snow from October/November continues to form a persistent weak layer of faceted snow on slopes facing west through north through east aspects at mid and upper elevations. Although triggering an avalanche is becoming less likely, human-triggered avalanches 1–2 feet deep and up to 100 feet wide remain possible.
Photo (BC 101): A classic slab-over-weak-layer structure on northerly-facing terrain.
I can’t remember forecasting wet snow avalanches this close to the solstice before. Today, 700 mb (10,000') temperatures climb to +6 °C (42.8 °F) as high pressure takes control. That’s enough warming to put wet snow avalanches on the table across the range, on all aspects, and at all elevations.
On sunny slopes, the sun will warm the snow, and we can expect small, loose-wet avalanches throughout the day. On shady aspects at mid and upper elevations, the outcome is less certain. My hunch is that the snow surface has already seen some warmth and will remain firm and cold enough, especially with the low sun-angle. However, if you start seeing roller balls or unconsolidated, wet, mushy snow, it’s time to get out of there or head for low-angle terrain. Wet slabs are a mystery, but with these warm temps, I would be thinking about it.
Glide avalanches can be expected in the usual terrain of Mill B South, Broads, and Stairs Gulch of BCC, and in the upper reaches of Porter Fork in MCC.
No new avalanches were reported in the backcountry yesterday. However, backcountry observers continue to note collapsing on north-facing slopes.
Under clear skies, mountain temperatures range from 23 to 35 °F this morning, reflecting a strong temperature inversion. The wind continues to blow from the west-northwest at speeds of 10–15 mph with gusts into the 20s.
Expect mostly sunny skies today, with ridgetop temperatures climbing into the 40s °F near 10,000 feet. It's going to be warm. The wind should slowly decrease throughout the day as the center of high pressure moves overhead later today.
Consulting the crystal ball (and a whole lot of computer models), there’s some hope for a pattern change around mid-week. Snow totals are still very much TBD, but the good news is that models are pointing toward a more active and wetter pattern through the rest of the month. The meteogram below for Alta shows every ensemble member turning wetter around the 17th. Fingers crossed—we’re due. At the UAC, we call this sipping the GFS Kool-Aid
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.
