Dangerous thunderstorms producing an increased risk of flooding, damaging winds and even a tornado are sweeping across the Southwest. Is this common?

The WeatherRadar shows lines of thunderstorms spreading across Arizona and southern Utah today, with the downpours extending into western New Mexico and western Colorado this evening. Several inches of rainfall are likely, increasing the risk of flash flooding due to the canyons and poor drainage areas found across the Southwest.

This storm system is out of character for this time of the year due to its plentiful access to tropical moisture from the Pacific. This tropical influx is helping to destabilize the atmosphere, increasing the chance for damaging winds and even an isolated tornado.

This is a bit unique because most of the Southwest receives rainfall during the late summer and early autumn when the Southwest monsoon is active. Additionally, this rainfall will become more widespread compared to the more scattered nature of typical summer thunderstorms.

The same system bringing the Southwest downpours will produce rain later today across Southern California, especially in the greater Los Angeles area with some flood risk in the southern Inland Empire and the southern San Joaquin Valley.