Loose wet avalanches are surface avalanches involving moist or wet snow that has lost cohesion. They generally occur when the sun has had time to beat down a slope, especially in spring. While usually small, they have the potential to entrain lots of wet, heavy snow, making them dangerous if you get caught.
You can avoid them by staying off sun-affected slopes during the warmest part of the day, when the snow becomes wet or slushy. Choose shady slopes instead, or travel early in the morning, when the snow is still frozen.