This past Sunday Arias (who provides color commentary) and I hiked up at Boulder. We already knew it was likely unflyable since Sugarloaf had been showing strong west for 30-45 minutes, but wanted the exercise and I had hoped to capture how rapid the transition to west can occur. About 15 minutes prior to this video we saw one pilot take a sled ride in apparently benign conditions, though I do not know if they were aware of the danger that was lurking just behind them or not.
When we arrived at launch it appeared flyable with a steady east wind coming straight in 8g12. The only tangible indication that something was awry was the occasional switchy behavior of the ridgeline windsock, though it was not obviously west yet. However, weather underground was showing sugarloaf at 20g36 and a wind talker just 1-2 miles behind the hill reporting gusts to 40, so we kept the gliders in the bag and I pulled my phone out to capture the transition, with the launch transitioning from “flyable” conditions to gusting 25+ over the back in just 1-2 minutes. I have witnessed similar transitions at boulder at least 3-4 times on days with strong west uppers, so these events are not uncommon. But there’s nothing quite like seeing it for yourself to discover a newfound respect for the risk of flying on strong upper days.