The 12-16 inches of snow that fell last Saturday February 22nd has either bonded well to the snowpack below, or was displaced by strong winds the following week. Enough time has now passed that natural storm slab avalanches are unlikely. Areas of recently deposited wind slab may be susceptible to human triggering. The addition of new snow from an approaching storm arriving on Sunday night may increase the chances of both natural and human caused slides. No new avalanches have been reported since February 22nd.
Very strong to gale force winds blew out of the north-northeast between Sunday evening and Tuesday night. Average wind speeds exceeded 50 mph and gusts up to 84 mph were recorded at ASBTP (11,555’). The overall effect of the wind might have created dangerous wind slab, or reduced the hazard by blowing all of the snow away.
Near and Above Treeline:Where new snow has become scoured away, ice axe and crampons are strongly recommended as surface conditions can be very firm depending on the time of day, temperature, and coverage. Always be cautious of wind slab formation on steep, leeward slopes. Observe local signs of wind stripping and hollow drum sounds whenever you travel above treeline. Where wind has not scoured snow, depths remain at 3-5 feet. New snow falling on these firm surfaces may be reactive, potentially sluffing with little provocation. Approach steep terrain with caution.
Below Treeline:With a decrease in elevation comes a decrease in snow depth. Obstacles become the main hazard below 9500 feet, but are present on all aspects at all elevations. Sunny and southerly slopes below 9500 feet are getting difficult to navigate on skis. Always expect the unexpected. With recent new snowfall, obstacles have become covered and hidden just below the surface. Ski and snowboard with care.
Lower elevation terrain has received enough warm temperatures so that the snowpack is nearing an isothermal state. This means the entire snowpack is near the freezing point. Under this condition, the snowpack is generally strong, and has a well-bonded structure when frozen together at night. Rapid warming and air temperatures in the high 40°s F can weaken the structure resulting in wet avalanches. Avoid steep terrain when the snowpack becomes too sloppy for enjoyable travel. In an isothermal snowpack, conditions can degrade rapidly.
Wind transported snow was evident throughout the past week. During several days ideal saltation (wind transporting snow) velocities were recorded at 11,555 feet. On Tuesday February 25th, gale force ridge-top winds out of the NNE stripped many windward slopes by the process of turbulent suspension, most likely returning much of our above treeline snow back to the clouds.
Still, pockets and even slopes of unstable wind slab (most likely hard slab) cannot be ruled out. Use caution on potentially wind loaded terrain, especially near ridgelines.
Although the forecast for the upcoming week looks cool and breezy, if mid-day temperatures exceed expectations, loose wet avalanches will be possible. These could occur primarily on lower elevations southerly slopes and near radiation absorbing terrain features, like rock outcrops above treeline. Lower elevation snowpack is becoming isothermal, so rapid melting can occur when temperatures rise into the upper 40°s F.
Join KPAC and crew for the Annual Mikee Linville Fundraiser event at Agassiz Lodge, Arizona Snowbowl, on Saturday March 28, 12-5 pm. Huge raffle of amazing prizes, including an unlimited Snowbowl Power Pass! This is our main education fundraiser and we hope to recoup the $8400 in scholarships awarded this winter...Thank you for your support and hope to see you there!
Always carry the 10 essentials and avalanche rescue gear for wintertime wilderness travel. Practice with your avalanche rescue gear. There is still space available in our avalanche courses.
Submit your observations here. You may save a life! The link to this form is now on our home page and snowpack menu.
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.
Weather updated Friday February 28
The Peaks received 10” – 16” of fresh snow on Saturday February 22nd. The storm began with rain at lower elevations below 8000 feet. Rainfall was even observed at 10,500 feet. The low-pressure system cleared from Coconino county late Saturday night, leaving clear skies and fresh snow in its wake. On Monday a dry cold front replaced the storm, bringing breezy conditions and cold temperatures to the region. Tuesday had the lowest temperatures, dropping down to 7°F at 11,555 feet. Tuesday also brought extreme winds out of the north and northeast causing the ski area to close for the day. Northerly winds continued throughout the week, with speeds in the high 20 mph range.
This weekend will bring clear skies with highs in the mid 30’s and lows in the high 20’s. Models show an approaching low pressure system bringing a potential for 2-6 inches of snow starting Sunday night and lasting until early in the workweek. Moderate to strong winds out of the west and northwest will follow this disturbance, dry and cool temperatures are likely afterwards.
Arizona Snowbowl reported a 58" (147 cm) base at 10,800 feet. Snowslide SNOTEL reports 22" (56 cm) at 9,730 feet. So far this winter, we have had 163" (414 cm) of snowfall at 10,800 feet.
Since February 23rd, SNOTEL temperatures have ranged between 41°F on February 24th and 3°F on February 26th. ASBTP station (11,555 ft) reported a low of 7°F on February 25th and a high of 40°F on February 27th.