A severe mid-latitude storm is forecast to hit the West Coast of the United States on Monday night and Tuesday, bringing a strong atmospheric river into Oregon and California. This low-pressure system is likely to undergo bombogenesis, or “bomb out,” a term used to describe low-pressure systems that intensify fast, usually with a pressure drop of at least 24 mb in 24 hours. The definition differs depending on latitude.
The storm system moving toward the west Tuesday through Thursday has the potential to more than double that pressure drop, with forecast models predicting a decrease of 50–60 mb in less than a day, starting at above 1000 mb Monday night and perhaps going below 950 mb by Tuesday night. This powerful storm system is likely to have a significant impact on portions of the Northwest and Northern California, bringing heavy rain, strong gusts, and large waves.
As the low-pressure system develops, it will tap into a source of subtropical moisture, resulting in an atmospheric river. These systems can produce heavy rain and strong gusts.
The University of California, San Diego, developed a scale ranging from 1 to 5 to help people comprehend and prepare for the effects of these systems. Some regions along the California coast might experience level 4 impacts, which fall into the “extreme” category.
From Tuesday to Thursday, Southern Oregon and Northern California should expect significant rainfall, with totals of a foot or more. floods in these places are expected, including river and flash floods.
If you reside in a low-lying location that is prone to flooding, prepare to evacuate in the event of a flash flood warning. Strong gusts could also bring down trees and power lines along the shore, particularly on Tuesday and Wednesday.
Winter Storm Warnings are in force for significant snowfall in Northern California’s higher altitudes through Wednesday.