In the West, a “bomb cyclone” — or a fast-strengthening storm that increases 24 millibars (a unit of pressure) in 24 hours — has resulted in heavy rain across the region and new evacuation orders for vulnerable, burn-scarred locations like California’s Santa Barbara County, where the accumumulation of debris flows poses a significant threat.
Additionally, the Sierra Nevada mountain range is predicted to see several feet of snow through early this week, compounded by 50-mile-per-hour-plus winds. Chain controls and roadway closures will likely lead to major travel delays.
The National Weather Service has also instated flash-flood watches in central and northern California, where some areas could see up to 10 inches of rain.
On Sunday, tornadoes, large hail and damaging winds were reported across Arkansas, Missouri, Illinois and Indiana, and the Storm Prediction Center shows a particular area from St. Louis to Springfield, Missouri as being at increased risk for tornadoes.
And by Tuesday and Wednesday, a nor’easter (named for its characteristically strong northeasterly winds) will likely hit the East Coast. Southern New England could see coastal flooding and heavy rain. It’s too soon to know specific forecast details, but urban and street flooding are possibilities, and some computer models predict more than six inches of rain for the area.
In the U.S., fall is widely considered a secondary peak season for extreme weather events, as the significant temperature shifts that come with the change of seasons can accelerate their development.