A storm last Thursday and Friday deposited 5 inches of snow at 10,800’ and since then conditions have dried out. No natural or human triggered avalanches have been reported. This Wednesday afternoon through Thursday morning brought extreme ridge top winds out of the north and northwest transporting available snow. Gusts of 85 mph were recorded at the ASBTP weather station at 11:10 pm Wednesday night. Snowpack stability tests today (north aspect 11,600') revealed inconsistent results, with moderate strength but varied energy in CT and ECT tests.
Wind speeds above 45-50 mph typically transport available snow aloft, sublimating (evaporating) back into the atmosphere, rather than loading leeward slopes. However, winds of moderate strength, 15-40 mph are effective at loading starting zones along ridge tops and terrain features of south and southeast aspects with the recent loading. Allow at least 24 hours for snow to settle and bond, natural and skier triggered avalanches may still be possible, although they are unlikely except in localized wind loaded terrain.
On lower elevation slopes, and on all slopes that have been scoured by wind or exposed to intense sun, buried obstacles and hazards still exist. Backcountry skiers and boarders will need at least another foot of snow for favorable travel conditions. Arcing your turns without scraping rocks and logs hidden below the surface is a rarity. Early season conditions will continue for at least another week.
Near and Above Treeline:Recent observations have shown variable bonding between November/December snow and old basal facets (depth hoar) from October snow. It appears that facet growth may have been slowed by an ice layer at the bottom of snowpack, which may have inhibited vapor flux. Also, depth hoar crystals have started to bond to one another on certain aspects, but facet metamorphism can continue into January.
Our early season shallow snowpack is becoming the persistent problem. Patience is key. Overzealous enthusiasm leads to poor decision-making. New snow accumulation is the first priority and bonding with the layers underneath second. The lack of new snow can give rise to the "scarcity heuristic trap". Because of wind scouring, snow coverage above treeline is increasingly variable. Hidden rocks and other obstacles are common. Ski with early season eyeballs and awareness in order to enjoy the rest of the winter, once coverage improves.
Below Treeline:Safe backcountry travel may be challenging due to shallow coverage at lower elevations. Until more snow falls, hidden stumps, logs, and rocks are significant hazards. Regretfully, KPAC cancelled our Level 1 Avalanche Course scheduled for Dec. 14-16 because of insufficient backcountry snow coverage.
High velocity winds from the north and northeast affected the Peaks on Wednesday through Thursday. Gusts exceeded 80 mph. Although there was limited snow available for transport, and winds of these speeds strip and sublimate more than deposit snow, still hard slab avalanches are a possibility . These are likely to be in smaller pockets, but could be triggered by a skier or boarder. Stay off of hollow sounding pillows of wind slab, be aware of whumping and cracking.
Be aware that even small hard wind slab avalanches carry significant destructive force, much akin to being caught in a rock slide of frozen blocks of high density compacted snow.
See our courses page for upcoming free courses, including a FREE Introduction to Avalanches Seminar at Aspen Sports on January 3.
Backcountry permits are required for travel in the Kachina Peaks Wilderness and available at local USFS locations, as well as, at the Agassiz Lodge on Saturday and Sunday 8:30 -11:30 a.m.
Uphill travel on terrain within the Arizona Snowbowl ski area is still closed. 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.
Over the week we have experienced seasonally normal to above normal temperatures. A wind advisory was issued by the National Weather Service (Flagstaff) from Wednesday afternoon to Thursday morning (Dec. 12-13) with the passing of a dry low pressure to our north. The weather station at the top of Snowbowl (ASBTP) recorded sustained winds of over 40 mph between 11:00 pm Wednesday and 9:00 am Thursday. A maximum gust of 85 mph was recorded at 11:10 pm on Wednesday.
The coming week will bring cloudy, but generally dry conditions. A cold Pacific disturbance will move through our region on Monday and Tuesday bringing mountain snow showers, but little chance of significant accumulation. This will be followed by building high pressure and warming, leading to above average temperatures by week's end.
On Friday morning December 14th, the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 12 inches (30.5 cm) at 9,730 feet. Arizona Snowbowl reported a settled base of 26 inches (66 cm) at 10,800 feet. So far this winter, 41 inches (104 cm) of snow have fallen at the mid-mountain study site. Since December 8th, SNOTEL temperatures have ranged between 15°F on December 13th, and 45°F on December 10th. For the same period the AZ Snowbowl Top Patrol Station (ASBTP 11,555 feet) temperatures ranged between 15°F on December 12th and 40°F on December 10th.