Natural and human triggered avalanches may be possible during this current weather pattern. Significant amounts of new snow and wind transported snow will raise the probability of natural and human triggered avalanches.
Current skiable terrain with sufficient coverage is mostly on wind protected slopes and/or northerly aspects. Year to date snowfall is at 83", with a base of @ 36".
Persistent weak layers have been an issue this year. See AZ snow pit data at snowpilot.org - link also under the snowpack menu.
No human triggered avalanches have been reported this season. No significant natural avalanches reported since the small loose-snow avalanches of February 28, 2018. On Monday, March 12th some small loose wet avalanches were reported in Humphrey's Cirque - see photo below.
Near and Above Treeline:With new snow and wind, new wind slabs may form on leeward aspects. With the past week's warm weather, expect to find new melt/freeze crusts on many aspects. Crampons may be helpful in freezing weather where the melt/freeze crust is hardest/thickest. New snow may not bond well to these crusts.
A weak layer of basal facets exists on northerly aspects, and has been reactive in some testing. Also, check for stratification of weak layers in wind slabs on previously loaded slopes.
Below Treeline:With ~36" (94 cm) undisturbed settled snow depth at 10800' (NW aspect), rocks and logs remain primary hazards.
Most northerly aspects will have the best coverage with measured depths at 10000' ranging from 22 to 50" (56 cm to 127 cm), while south facing slopes range from no snow to 28" (71 cm) in favored locations near treeline. Melt/freeze crusts have developed on most aspects.
The snow depth is highly variable due to wind transport and sun affect, aspect dependent.
New snow and wind are in the forecast. Should significant precipitation occur, then watch for unstable slab development. Post storm, warm temperatures and sunshine may destabilize newly formed storm and wind slabs.
Stay away from convex pillows of wind-drifted snow on the lee side of ridges and other terrain features. Wind slabs may have a chalky look and feel. Wind slabs can be very hard, and may present a hollow drum like sound as you traverse across slope. Snowpack tests conducted in wind-loaded areas may reveal a wind slab problem in the upper few feet of the snowpack.
Cohesive slabs above weak basal facets are potential areas of instability. Northerly and Easterly slopes will be the main suspects.
Be cautious of previously loaded terrain - old wind slabs on northerly/shaded slopes may have persistent weak bonds.
This problem is not widespread and the probability of triggering a persistent slab is presumably low. However, significant amounts of new snow and wind loading will increase the probability of collapsing persistent weak layers in the older snowpack stratigraphy.
New snow accumulations may approach 12" in favored, high elevation locations. Wind transport will increase the likelihood of storm slabs on leeward ridgeline aspects and localized terrain with cross loading above tree line.
Mikee Lineville Backcountry Scholarship fundraiser coming up! March 31st, Saturday afternoon on the Agassiz Deck. Live music, raffle, silent auction. Yahoo! Funds go directly to students to help pay for avalanche courses.
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 until 11 a.m.
Uphill travel on terrain within the Arizona Snowbowl ski area is now open.
Please refer to www.flagstaffuphill.com and https://www.snowbowl.ski/the-mountain/uphill-access/ for details.
Last updated on Thursday March 15, 2018
After a week of unsettled weather, which produced 4 inches of snow at 10,800 ft. last weekend, and another 4 inches (at upper mountain elevations) on Thursday, another storm is building for this Saturday afternoon and evening. Weather models have taken their time to agree upon a unified outcome.
Predicted snow loading continues to be a bit of a crapshoot. Recent models seem to favor a wet forecast, with the possibility of 5-12 inches of new snow at and above treeline, but don’t bet your last dollar on this accumulation. Winds out of the southwest will be strongest as the storm approaches, and will blow at optimum velocities to transport snow onto leeward slopes.
Snowfall should taper off by Sunday midday, introducing a warming and drying trend for the first half of the workweek as high pressure ridging develops.
The next possibilities for fresh snowfall will be around Thursday March 22nd with the arrival of another Pacific storm. At the time of publication, it was too far out to predict snow amounts, however, this storm seems on the warmer side so the snowline will probably be above 8,000 feet.
On the evening of March 15th the Inner Basin SNOTEL site (Snowslide) reported a snow depth of 23 inches (58.5 cm) at 9,730 ft and Arizona Snowbowl reported a settled base of 40 inches (101.5 cm) at 10,800 ft. So far this winter 80 inches (203 cm) of snow have fallen at the mid-mountain study site. Since March 8th the SNOTEL temperatures have been mild, ranging between 22° and 50° F. For the same period, the AZ Snowbowl Top Patrol Station (ASTP - elev. 11555 ft) temperatures ranged between 16° and 41 ° F.