Weather System Threatens Southwest with Rain and Flooding

Potential Heavy Rain and Flooding Threat

A weather system is pulling tropical moisture toward the southwestern United States. This pattern could result in heavy rain, flash flooding, and mountain snow over Halloween weekend. Several states may experience renewed flooding after recent storms.

Rainfall in Southern California

AccuWeather meteorologists report significant rainfall could impact Southern California. The threat level depends on how storm systems combine with moisture from the Pacific. This setup may create an atmospheric river, a concentrated corridor of water vapor. If this corridor extends from Hawaii to the West Coast, it might become a Pineapple Express.

A Pineapple Express carries warm, moisture-rich air from the tropical Pacific toward North America’s West Coast.

These systems can provide much-needed rain to drought areas. However, they can also cause dangerous conditions if too much rain falls quickly.

Potential Impacts and Risks

AccuWeather’s map shows storm systems approaching from Alaska and near Washington state, drawing tropical moisture from Tropical Rainstorm Olana near Hawaii. Meteorologists predict limited rainfall across major Southern California cities, with some mountain slopes receiving up to 3 inches. A scenario with combined systems could bring more rain and heighten flash flood risks.

Southwest Flooding Concerns

States like Arizona, Utah, New Mexico, and Colorado face more significant rainfall risks. These areas could see 1 to 2 inches of rain, with upslope regions receiving 2 to 4 inches. AccuWeather’s Local StormMax forecast predicts up to 7 inches.

Recent heavy rains have already impacted parts of the region. The San Juan Mountains in New Mexico and Colorado saw 5 to 10 inches of rain last week, causing flooding and record streamflows. Continued downpours heighten flood risks in cities like Phoenix, Flagstaff, Durango, and Farmington.

The storm system might also bring showers to the Pacific Northwest and snow to the Rocky Mountains’ higher elevations, including Montana, Idaho, Wyoming, Colorado, and Utah.

Forecasters remain vigilant as more details about the developing weather pattern emerge.