**Record-Breaking Storm to Unleash Severe Weather Across Northwestern U.S. and Canada**

An unprecedentedly strong low-pressure system is forming offshore, set to bring up to 20 inches of rain to California and a range of severe weather conditions across the northwestern United States and Canada. This powerful system is predicted to develop off the coasts of Oregon and Washington on Tuesday, bringing along an atmospheric river stretching about 2,000 miles from Hawaii to Northern California.

Meteorologists are warning of multiple hazards that will extend into the weekend, including significant rainfall for Northern California's Coast Ranges and heavy snow for the Klamath Mountains. Forecasts predict 10 to 20 inches of rain for California and similarly heavy snow over higher elevations. The same system will also affect Oregon, Washington, and British Columbia with intense rain, snow, and potentially damaging winds. Snow is also expected to fall in Idaho, Montana, Alberta, and Saskatchewan.

Atmospheric rivers, which transport moisture and heat from the tropics toward the poles, play a significant role in this event. The incoming atmospheric river, anticipated to be a Category 4 (out of 5), is notable for its long duration. However, it's the exceptionally intense low-pressure system propelling it that stands out. This system, projected to deepen rapidly from about 984 millibars to 943 millibars within hours, qualifies it as a "bomb cyclone," a term used when a storm's central pressure drops by more than 24 millibars in 24 hours.

Analysis of historical atmospheric pressure data indicates that this could be the most intense November storm on record in the region, with an intensity comparable to a Category 4 hurricane. The storm's trajectory will be influenced by a convoluted jet stream pattern, further intensified by a marine heat wave in the North Pacific, contributing to the storm's severe nature.

As the storm progresses, a secondary low-pressure system is expected to form offshore late Thursday into Friday, bringing another surge of heavy rainfall and mountain snow. A blizzard warning has been issued for the Cascade Mountains of Washington above elevations of 2,500 feet, with forecasts predicting snowfall exceeding a foot and wind gusts reaching 60 mph. Similar conditions are expected in British Columbia, particularly on Vancouver Island and the nearby mainland mountains.

The storm is anticipated to weaken over the weekend, with less intense rain and snow. However, this event may signify the beginning of an active winter season across the Northwest, underscored by a La Niña-like pattern and a vigorous northern jet stream.