Over the past week, a deep atmospheric trough off the West Coast directed heavy rain and high winds across Northern California, Oregon and Washington. Then, its southern portion split away and strengthened off the coast of Southern California; this "cut-off low" is now sweeping torrential rain across San Diego, Los Angeles and the adjacent mountains.
Prolonged, heavy rain will be especially problematic in the burn scar areas, likely producing mudslides and landslides. On the positive side, the Southern Sierra Nevada may receive up to three feet of snow, a welcome, early addition to the vital winter snow pack.
After pummeling Southern California, the storm is expected to move across western Arizona and southern Nevada before dumping significant snow in the mountains of Utah and Colorado. Unfortunately, a second Pacific storm system may form in its wake, augmenting the potential for widespread flooding across the arid landscapes of the Desert Southwest.
