Dramatic Shift in Weather Pattern for the West to Start the Week

Fall is in the air across the western U.S. A southward dip in the jet stream is bringing down significantly cooler air just as the North American monsoon season wraps up to the south. Here is a look at what is happening across the West Coast this week.

Change in the Weather Being Felt in the West

A noticeable change in the overall weather pattern is being felt in the western part of the country this week. In the Southwest, the change in the weather will mean the end of the annual North American monsoon season. The last of the moisture associated with this yearly pattern will bring the chance of localized flash flooding to this corner of the region.

The last gasp of the monsoon moisture will be accompanied by what is left of the former Tropical Storm Ileana. While the feature officially lost its defined tropical characteristics on Sunday, there is still a good amount of moisture flowing up to the north. This influx of tropical moisture will end up falling across the deserts and mountainous terrain of New Mexico and Colorado to start the week.

The surge of tropical rain will merge with the lingering moisture from the monsoon impacts, amplifying the overall precipitation amounts in the Southwest. This degree of rainfall will be enough to create the risk of flash flooding and gusty thunderstorms. A number of cities will be under the threat of flooding including Arizona metro areas Phoenix, Tucson, and Flagstaff. This threat will expand into southwestern Colorado and over into portions of New Mexico.

Hikers heading out should be aware of the risk of sudden downpours. It does not take long for canyons and arroyos to fill with floodwaters. Mudslides and other dangerous debris flows are also a potential danger that outdoor enthusiasts will want to consider when making plans.