Human triggered avalanches possible on new wind slabs and warming slopes. Natural avalanches possible on slopes affected by solar input, primarily southerly and westerly aspects. But other slopes may become suspect. The Agassiz Peak Weather Station did not drop below freezing last night.
On March 8th, small loose wet snow avalanches released on southern aspects, above treeline in Humphreys Cirque. No large natural avalanches reported since the Feb. 27/28 storm. No backcountry travel triggered avalanches reported since January.
A warming trend and strong winds from the S/SW to W/NW has created variable and hazardous conditions; including but not limited to hard wind slabs on crusts and near surface faceted layers, and solar radiation creating and potentially detaching wet slabs on weak layers.
Wind loading on N to NE slopes below ridge lines was influenced by SW winds (25-35 mph) occurring over 3/4 -3/5. These winds contributed to cornice building along ridges adding to the potential hazard of cornice collapse.
Near and Above Treeline:Wind slabs... See overall above.
Hard wind slab and rime ice may be found above treeline. Ice axes and crampons may help prevent a slide for life on steep icy slopes. Much of the snow above treeline and some below has been wind affected.
Dangerous overhung cornices with large cracks have been observed on Humphreys Peak Ridge and Hardcore Ridge. These are fairly unusual locally, at least in terms of the extent of overhanging structure. Don't be caught off guard! Cornices can be extremely dangerous as they can collapse under the weight of a person, or with warming temperatures, and potentially trigger avalanches on slopes below. When traveling on ridges, give cornices wide berth, by using route finding well to the windward side of the ridge.
Unstable wet snow may develop as treeline temperatures push 50° F. These conditions will be found primarily on southerly and westerly aspects. First at lower elevations, and then progressing towards treeline and above treeline into open terrain. Wind slabs on any aspect may become more sensitive if the slope receives significant solar input.
With temperatures projected to stay high over the next week, the possibility exists for skier triggered avalanches in warm wet snow. Possibly producing small to large slides as conditions warm.
Below Treeline:Watch for snowballing, pinwheels and other signs of instability created by significant warming temperatures above freezing. Make conservative terrain choices in regard to slopes and paths that lead into or cross terrain traps. Below treeline temperatures will likely not drop below freezing, possibly creating dangerous isothermic conditions on isolated steep slopes.
As warm spring temperatures take hold, watch for deep slush, snowballing, pinwheels, and small wet slough indicating the potential for larger wet sloughs or wet slab releases. Keep an eye on the Agassiz Weather Station which is near treeline. If overnight temperatures do not drop below freezing then wet avalanche hazard will increase near treeline. The Agassiz Peak Weather Station did not drop below freezing last night!
Below treeline temperatures will be even warmer, possibly creating dangerous isothermic conditions and/or potential slab releases on isolated steep slopes.
Southerly and westerly aspects will be your primary culprits, but this may be our warmest period yet of 2017, so any slope that gets significant sunshine or ambient heat from surrounding features will be suspect. Wet conditions will be initially evident at lower elevations and progress higher later in the day.
Watch for windslabs developed earlier this week. These may become more sensitive with warming temperatures and solar input. Shooting cracks and hollow sounds under foot will indicate unstable wind slabs. Or you may get no warning at all, so best to stay off of large wind-loaded convexities.
Always keep in mind, wind slabs are unpredictable, and may support the weight of a skier or rider initially, and fail suddenly with tragic consequences. Avoid snow surfaces which are recently loaded, sound hollow, have signs of fracturing, cracking, or whoompfing sounds.
This season numerous rescues have been conducted by Coconino County Search and Rescue, and the Arizona Snowbowl Ski Patrol. Some of these could have been avoided by better planning and preparation.
Travelers are advised to exercise caution, make slope specific evaluations and most of all, know where you are going and be prepared for the unexpected.
As always, please treat this summary with appropriately guarded skepticism, make your own assessments, and contribute to our body of knowledge by reporting your observations.
Arizona Snowbowl uphill policy.
During winter, backcountry permits are required to access the Kachina Peaks Wilderness. More info
Last updated on Thursday, March 9, 2017
Strong to moderate winds blew from nearly all directions earlier this week before a warming trend took hold. Expect well above normal temperatures and dry conditions through the early part of next week. Expect temperatures to be 10 to 15° F above normal. Over the next 7 days fair conditions will dominate, but weak disturbances brushing past the region may occasionally result in breezy southwesterly winds.
On Thursday evening, March 2nd the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 82 inches (208 cm) at 9700’, and Arizona Snowbowl reported 99 inches (251 cm) at 10800'. Since March 3rd SNOTEL temperatures ranged between 2° and 55° F and Agassiz station between 5° and 47° F.