As cooler temperatures move over the eastern U.S., the West is forecast to see heavy rain and mountain snow, including what's known as a "bomb cyclone" near the Northwest.
Fox News' Janice Dean said Thursday that some areas are expected to receive upwards of two feet, while California will reportedly experience debris flows, flash flooding and mudslides – a big hazard, especially in wildfire burn areas.
According to Seattle's KCPQ, the bomb cyclone is currently a few hundred miles to the west of Washington's coast and the storm appears to be tracking north.
The station said it appears the bomb cyclone "won't have much of an impact on the Pacific Northwest," though wind advisories remain.
The National Weather Service said earlier Thursday that the cyclone responsible for the development of an atmospheric river aimed at the West Coast and parts of British Columbia could bring rainfall totals ranging between two to five inches in the higher elevations.
So, what is a bomb cyclone and how is it formed?
A bomb cyclone is also known as a mid-latitude cyclone, according to the National Oceanic and Atmospheric Administration (NOAA).
Mid-latitude cyclones drive most of the stormy weather in the continental U.S., the agency notes.
A process called bombogenesis can occur when a mid-latitude cyclone intensifies rapidly over a 24-hour period, dropping at least 24 millibars of atmospheric pressure.
Typically, a range in millibar change is around 10 to 15 in that same timeframe.
This can happen when a cold air mass collides with a warm air mass, like air over warm ocean waters.
The formation of the fast-strengthening weather system is bombogenesis, which generates the bomb cyclone.
The effects of the fast-developing low-pressure system include high and intense winds and blizzard and white-out conditions with heavy snow, in addition to rainfall on snow that can cause flooding.
It's not unusual to get at least one storm per year and bombogenesis nor'easters occur frequently during the winter seasons.