A search and rescue organization that serves Mt. Whitney in the Eastern Sierra warned inexperienced hikers this week to avoid some of its higher trails because they’re still covered in slippery, slushy snow that has led to injuries, including a recent slip and broken ankle that required a helicopter evacuation. … This winter’s record-breaking snowfall has made summertime hiking, backpacking and mountaineering more challenging than usual, if not treacherous, around the Sierra Nevada and other California mountains.