There has been a substantial amount of talk about something called an "Atmospheric River" in recent days. Occurring most commonly in the Winter months, atmospheric rivers have the potential to bring significant flooding and large snowfall amounts to the West to Northwest regions of the United States, as well as some parts of British Columbia in Canada.
Atmospheric rivers occur when long, narrow corridors of moist, warm air from the tropics move toward the poles ahead of powerful storm fronts. They behave like rivers in the sky (hence the name) and have the potential to carry more water than the Mississippi River. They can be more than 1,000 miles long, up to 620 miles wide, and an average of 1.8 miles in depth. Atmospheric rivers have the potential to bring up to 25 inches of rain to a given area, which is why they are such a big deal during this time of year. They make up roughly 50% to 65% of California's annual rainfall, according to the National Weather Service.
Keep the phrase "Turn around, don't drown" in mind while driving during during these types of events. You never know how deep the water on the road is until it is too late.