There are many ways to define winter. There's astronomical winter, which runs from the winter solstice (about 21 December) to the spring equinox (about 20 March). There's meteorological winter, which includes the months of December, January, and February. Finally, there's Steenburgh winter.
Steenburgh winter is that period during which we have the crème de la crème of backcountry powder skiing with both a deep snowpack and a low-angle sun. It starts when we hit 100 inches at the Alta-Collins snow-depth sensor. Anything less is still early season conditions. I've been amazed at what people have been skiing this year, but there are still plenty of unburied rocks, brush, and pucker trees out there.
Steenburgh winter ends on February 10th, which seems to be the day that the sun begins to have an increasingly caustic effect on the snow. South aspects don't survive more than a day or so after a storm, the cone of shadow on clear days becomes increasingly confined to northerly aspects, and the sun becomes increasingly important to consider in your backcountry travel plans. Note that concern about warming on south facing slopes got a mention in today's avalanche report, which we can expect to see more of in the coming weeks.
|Excerpt from the Utah Avalanche Center advisory for February 11, 2013|
Many have accused me of being a powder snob, and Steenburgh winter is all about such snobbery. It concentrates on that period when powder can linger for long stretches in the backcountry without much solar molestation. Of course many powder days come after the end of Steenburgh winter. In 2010/11 we were getting freshies on Memorial Day.
However, as we move farther away from Steenburgh winter, the sun will tighten the noose on backcountry powder following storms and it will be imperative to plan and adjust for its caustic effects.