What a great season everyone, and THANK YOU for your support! No significant skier triggered avalanches reported for the 2018/2019 season. Let's keep up the diligence and reflection that is required to stay alive in avalanche terrain.
The spring melt/freeze (m/f) cycle continues, with occasional interruptions by mild winter storms which have been windy and mostly dry. Since March 23rd we've only seen about 6" of new snow near treeline. Total season snowfall is about 130% of average.
Wet avalanches will be possible on steep slopes where the snowpack melts from warm days, sunshine, above-freezing overnight temperatures, and/or rain. Watch for saturated and deep slushy snow around terrain traps and any slope steeper than 30°. Warm temperatures and consistent nights with above freezing temperatures will precede an unstable and wet snowpack. If you sink into the snow up to or above your boot top, then it is time to reevaluate your plan.
Last known significant slab avalanches occurred in February. More recently, during March and April, D1.5 (destructive size) loose wet avalanche debris were observed on southeasterly slopes near/above treeline, and on April 9th D1.5 debris were observed on a northerly aspect below treeline. D1.5 avalanches are relatively small but can be strong enough to injure and possibly kill an animal/person.
Springtime avalanche tips at BCA.
Near and Above Treeline:Expect to find wind scoured zones and hard icy snow above treeline. Crampons and ice axes will help prevent falls on steep icy slopes.
If we do get a significant snow event, watch for new storm/wind slab development. When the sun and warmth return post-storm, new slabs will be the first to saturate and possibly produce wet avalanches.
Below Treeline:Coverage is good on most slopes above 10,000', with plenty of safer low angle (<30°) touring. Southerly and sunny slopes are rapidly losing snow as we push into spring.
As the days heat up, watch for loose wet and larger wet slab avalanche potential. Wet avalanche debris were observed recently on a north aspect of Doyle Peak, near 10,500'. See previous summary. There was a report last week of wet avalanche debris below the Heck Yea chute - a southeasterly slope at 12'000'.
Rain on snow can produce wet avalanches.
"Heating happens fast this time of year, with snow changing in a matter of minutes. Watch for the usual signs of wet instability including roller balls, point releases, and damp, heavy, loose snow. You’ll need to constantly monitor snow surface conditions […] Keep in mind what you’ll be traveling under as you exit the mountains [during the heat of the day]" -Utah Avalanche Center
Cornices have formed along ridgelines and cross loaded features. Stay away from the edges of tall and/or overhung cornices, as these may collapse unexpectedly and break further back than you may expect. Cornices loose strength and collapse during warm spring weather. Image of cornices in the April 5th summary.
If we do get a significant snow event, watch for new storm/wind slab development near and above treeline. Pay attention to snowfall amounts, wind, and bonding of new/old snow. New slabs may have a hard time bonding to cold frozen m/f crusts. These crusts have formed on all aspects. When the sun and warmth return post-storm, new slabs will be the first to saturate and possibly produce wet avalanches.
Logging began along the first 1/4 mile of Freidlein Prairie Road (FR-522). Loggers will plow that stretch of road and need gate access. This is part of the Chimney Springs thinning project.
For information on uphill travel within the Arizona Snowbowl ski area, please refer to www.flagstaffuphill.com and https://www.snowbowl.ski/the-mountain/uphill-access/ for details. Access to the Kachina Peaks Wilderness is available from the lower lots at Snowbowl via the Humphreys Trail and Kachina Trail.
Weather updated on Thursday April 18.
Snowbowl recorded 4 inches of new snow and windy conditions on Friday April 12. Another lonely inch fell on Tuesday April 16. With the passing of these weak cold fronts to our north, we have seen sporadic winds out of the southwest and then shifting to northwest and north. Between storms, spring conditions have prevailed.
For the weekend and early workweek, expect favorable spring conditions, interrupted by a slight cool-own, more wind and potentially light precipitation on Monday, April 22. This will be followed by a building high pressure ridge and a return to cool nights, warn day’s and breezy afternoons. This springtime pattern will continue with the occasional low pressure trough passing to our north delivering wind, mid and high level clouds and an occasion light dusting of high elevation snow.
On Thursday, April 18 the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 42” (107 cm) at 9,730 feet. Arizona Snowbowl reported a settled base of 81” (206 cm) at 10,800 feet. So far this winter, 332" (843 cm) of snow has fallen at the mid-mountain study site. Since April 12, SNOTEL temperatures have ranged between 16°F on April 13, and 55°F on April 18. At ASBTP (11,555'), temperatures reported over the last week were between 15°F on April 13, and 52°F on April 18.
This has been a great winter. According to Snowbowl records from the mid-mountain study site (10,800’), this winter has been the 4th snowiest in 2 decades.