West Coast Bracing for Flooding
A series of very menacing storm systems is moving closer the the western coast of the United States, bringing with it many weather dangers from heavy down pourings of rain to epic amounts of higher elevation snows. And by epic we are talking about over 100 inches of snow! The storms are feeding into a plume of tropical moisture that extends out from the tropics. This type of weather pattern is very rare and is referred to as an atmospheric river. These weather events can benefit the West but they also can dump so much rain so quickly that major flooding occurs.
In addition to flooding concerns, there is also a big risk for mudslides in areas that had forest fires this past summer. When a mudslide occurs in a burned area, debris flows result because the fires have cleared out most of the vegetation that helps hold soils together and absorb water. A debris flow happens quickly and when it rushes downhill, it can swallow and overwhelm anything caught in its path.
Atmospheric river storms which occur during the winter are also called “Pineapple Express”. This is because this type of system is associated with heavy precipitation from the waters adjacent to the pineapple growing region of the Hawaiian Islands. This type of weather phenomenon is a warm storm that can cause extensive damages including flash floods, mudslides and melting snow that turns into more flooding.
Anywhere from 10 t0 20 inches of rain is expected to fall on the West Coast with around 12 inches expected in the coastal mountain ranges which will increase the threat of widespread flooding. In December of 2006, a Pineapple Express’ brought intense rains and record-breaking floods to the western portion of Washington. Many homes there were filled with mud and debris. There is great concern that the current system could do the same and not only to Washington but to areas of Oregon and mid-to-northern California.
The large area of low pressure that is spinning off the west coast will push several storms to land. The first storm can ashore Wednesday and dumped a lot of rain on the Casades and Sierra Nevada. The National Weather Service has storm warnings and flood watches and warning in effect up and down the West Coast which are expected to last through the weekend. The new storms which will spin out of the system will dump very heavy rains and record snows in mountainous regions along with high gusting winds.