For the next few days, human triggered avalanches near and above treeline may be possible where winds have created new slabs. However there are decreasing amounts of powder snow available for transport, and the probability of new wind slabs is waning.
With warm weather this weekend, small, wet avalanches may be possible on steep slopes - primarily sun exposed slopes below treeline. By Monday, January 6, temperatures are forecast to cool down and wet avalanches will become unlikely. Should a significant storm sneak up, or should temperatures warm significantly, then expect increasing avalanche hazard.
The Christmas storm cycle (36" of snow) produced several natural avalanches. A large storm slab avalanche occurred on the North face of Fremont Peak (Telemark chute). Depth of debris exceeded 2m in some spots. Observations suggest that the failure occurred at or above the new/old snow interface. See below photo. There appeared to be significant avalanche debris near the bottom of the Silverton chute - a northerly aspect to the east of the Telemark chute. Debris from a small storm slab release were noted on a northeast aspect of Doyle Peak (Telescope chute). Some debris was noted on a north aspect of Core Ridge.
Surface hoar was found on Doyle Peak (see photo below). This may become a weak layer, should it persist and become covered by new or windblown snow.
We have a complex snowpack that is highly variable depending on aspect and elevation. Review the snowpits.
Near and Above Treeline:Exposed terrain above treeline (generally 11,500') has been scoured with robust north winds (70+ mph) since December 29, resulting in hard wind slabs on south and cross loaded east and west aspects. On December 30th, some reactivity was noted on southwesterly slopes where a small layer of intact stellar snow was overlaid by a harder, 13 cm thick wind slab. The buried December 4 rain crust was reactive under several feet of new wind slab on isolated west aspects at 11,700', but we have not seen wide spread reactivity of the facet layers associated with these rain crusts.
Ice tools and crampons are recommended for safe travel, to help prevent slides for life on hard snow and ice. Watch for new wind slabs and cross-loading of chutes and gullies near ridgetops or in open bowls. However, there is not much powder snow available for transport, and the probability of new wind slabs is decreasing.
Coverage near treeline is generally 1.5m or more. If you are on your game in terms of stability assessment, route finding, and safe travel practices, there is plenty of safe fun to be had. The best snow has been found on wind sheltered terrain between 10,500' and 11,500' (treeline).
Below Treeline:As temperatures heat up over the weekend, watch for wet unstable snow on steep (>35°) and warming/sunny slopes.
Coverage for ski touring on many slopes above 9,500’ is very good for this time of year, but early season hazards such as downed trees, stumps, and boulders may still remain hidden - especially on sunny and wind scoured slopes. At lower elevations (<9000’) new snow will hide obstacles just below the surface. A melt/freeze crust has developed on many slopes below 10,000'.
Northerly and Westerly winds are forecasted over the weekend. Watch for new wind slabs and cross-loading of chutes and gullies near alpine ridgetops. There is not much powder snow available for transport, and the probability of new wind slabs is decreasing.
With warming temperatures over the weekend, watch for the release of wet unconsolidated snow or slush. This problem will likely be limited to steep (>35°) and sunny slopes below treeline. Wet avalanches will likely be small.
We noted that small wet slabs were releasing off roofs today in Flagstaff.
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 January 3rd
New Year’s week was windy and cold. On December 28 the coldest high daily temperature so far for this season was recorded. The high for the day was 13° F at ASBTP station (11,555’). Strong winds blew out of the NNE from 10:30 pm on December 28, to 8:30 pm on December 29. Their mean velocities at ASBTP station exceeded 40 mph during many recording intervals, and reached maximum gusts of 70 mph. Wind chill temperatures fell to -20° F.
A brief period of high pressure and some superficial warming on Monday and Tuesday was followed by a dry cold front dropping in from the north on New Year’s Day. The impact lasted through Thursday January 2nd, bringing a return of cold and windy conditions, but only one inch of new snow. Wind chill temperatures have consistently dropped below 0° F throughout the week.
Looking forward, it is shaping up to be a pleasant weekend with the warmest temperatures since December 23rd. Cool, blustery conditions will resume next week, with the greatest chances of precipitation too far out for accurate prediction. For the time being we have entered a less favorable pattern, so expect a period of dry conditions.
Of special note, snowfall so far this season of 129" is just an inch shy of meeting 50% of our mean annual total, so we are doing pretty well for being only 1/3 into our winter season.
Arizona Snowbowl reported a 60" (152 cm) base at 10,800 feet. Snowslide SNOTEL reports a 43" (109 cm) snow depth. So far this winter we have had 129" (328 cm) of snowfall at 10,800 feet.
Since December 27th, SNOTEL temperatures have ranged between -4° F on December 28th and 43°F on January 1st. ASBTP station (11,555 ft) reported a low of 0° F on December 28th and a high of 33° F on December 31st.