Ogden Avalanche Advisory Saturday, February 21, 2009 Created at 7:45 am Updated at 8:02 am Forecaster: Evelyn Lees BOTTOM LINE Danger by aspect and elevation on slopes approaching 35° or steeper. Out of the wind affected terrain, the avalanche danger is generally LOW. In the wind affected, upper elevation terrain, there is a MODERATE avalanche danger on steep slopes with wind drifts and along the corniced ridgelines. The avalanche danger may rise to MODERATE on steep sunny slopes and at low elevations with daytime heating, with human triggered damp sluffs possible. CURRENT CONDITIONS It feels like winter has turned the corner, with more sunlight and mild weather creating superb days for turning, riding, and snowshoeing. Excellent powder remains on most shady, northerly facing slopes down to surprisingly low elevations, though the powder is increasingly hemmed in by breakable sun crusts on east, south and west facing slopes, and some wind damage in the high elevation, exposed terrain. Under clear skies, temperatures in the Ogden area mountains are in the upper teens to low 20’s this morning. After the moderate southwesterly ridge line winds in the Ogden mountains yesterday, speeds are now almost calm. RECENT ACTIVITY Avalanche activity yesterday included a slab released with a ski cut on a steep, north facing slope of Mill Canyon Peak in American Fork, which was a foot deep by 50’ wide, failing on facets and at least one new snow slide triggered either by a natural cornice drop or wind drifting. THREAT #1 - Over the next 24 hours. Yesterday, the northwesterly winds were dancing along the higher ridgelines, kicking up plumes of snow, and creating new wind drifts. These drifts will still be sensitive today, and most widespread on slopes facing the east ½ of the compass. Field work indicates there are still a few isolated places where a slightly deeper slide could be released on faceted snow, 1 to 2 feet deep, and I suspect these pockets may be more widespread in the mid elevations of the Ogden mountains. THREAT #2 - Over the next 24 hours. Cornices are certainly no smaller today than they were a few days ago, and some actually grew yesterday and remain quite sensitive. There have been several close calls this past week, when they have broken back further than expected. If you want to drop a cornice, use a knotted cord or rope, and make certain no one is below you. THREAT #3 - Over the next 10 hours. Today’s sunny skies, warmer temperatures and calmer winds will increase the chance for wet avalanche activity. Once the snow surface becomes damp or sloppy, avoid travel on and below steep sunny slopes. Low elevation, shady slopes could heat up, sluffs will be easily triggered, running on faceted snow or hard icy crusts. So be careful when making afternoon exits on steep sunny slopes or low elevation shady slopes. MOUNTAIN WEATHER High pressure centered over Utah will bring sunny skies, with temperatures warming to near 40 at 8,000’ and into the upper 20s at 10,000’. The light northwesterly winds will shift to the southwest this afternoon, and increase into the 10-15 mph range, with gusts in the 30s. A moist, west to southwesterly flow will replace the high pressure for the coming week, with clouds increasing on Sunday, and the first chance for snow around Monday.