Today marks the 144th - and last - Aspen zone backcountry forecast for the 2016-17 winter. Starting this afternoon, we'll publish statewide avalanche summaries each Sunday, Wednesday and Friday through the end of May. We'll continue to issue zone weather forecasts for 11,000 feet twice a day until the end of April.
Thank you to everyone who's contributed observations so far this winter. Special thanks to people who reported unintentionally triggered avalanches and/ or close calls. These are invaluable to other backcountry travelers, and they help us to confirm or fine-tune our forecasts. If you're out and about over the next six weeks, please let us know what you see. It doesn't need to be dramatic or technical; just report some basics information about where you went, what kind of slopes you rode, and what the snow was like. Alerting us to any recent or triggered avalanches can be especially helpful.
A classic diurnal Springtime snow and avalanche cycle is underway and with no storms in sight, looks to continue for the next week or two. Mostly clear skies and up to eight hours of temperatures below freezing mean a solid, lasting refreeze of the near surface snow this morning. Surface crusts will soften as they receive direct sun and temperatures warm, and Loose Wet avalanches will become a concern by midday. These conditions will develop first on steeper, easterly slopes, then progress to westerly and northerly slopes.
The safest and best riding is when your skis or board sink less than an inch or two into the snow surface. Head for colder, shadier slopes if you're trenching into the snow or your turns are releasing small sluffs. Avoid being on or under very steep, rocky slopes if you see fresh rollerballs or fan-shaped point-releases. If you're punching through surface crusts, dangerous conditions may be developing. These are most likely above about 13000 feet, where recent warming and sun have only affected the near-surface layers of the snowpack and meltwater may be reaching older weak layers for the first time. Saturated snow can produce larger Loose Wet avalanches that gouge into older snow, as well as Wet Slab avalanches. It's easy to avoid these dangers by simply exiting this terrain early, before these conditions develop.
Stay alert for isolated slopes where more winter-like conditions are lingering. These are confined to shady slopes above about 13000 feet. These slopes may harbor old wind slabs and buried persistent weak layers under thin surface crusts. Rely on the tried and true signs of danger, like collapses and shooting cracks, so you can avoid triggering a small avalanche with outsized consequences.
The sustained warming is weakening cornices, and the potential for Cornice Fall avalanches is increasing. All too many avalanche fatalities occur when people ride or walk too far onto a cornice and it collapses, sending them down steep slopes below. Avoid this by staying off of and out from under overhanging drifts.