Mario's Remnants on the Way to Southern California and the Southwest

The southwestern U.S. and Southern California have been put on alert for a surge of moisture as Tropical Storm Mario sends rain into this corner of the country. Here is what you need to know about the anticipated impacts of this tropical weather maker.

Tropical Storm Mario Hanging On as it Targets the Southwestern U.S.

After weakening over the weekend, Tropical Storm Mario found new life on Monday as it churned across the Eastern Pacific. The storm is spinning just off the western coast of Mexico, moving to the northwest at 13 mph. As of the late Monday update from the National Hurricane Center (NHC), Mario was packing maximum sustained winds of 65 mph.

It is rare for tropical weather events that originate in the Eastern Pacific to impact Southern California. However, the latest forecast models indicate that Mario's remnants could filter into this region later in the week, increasing the chances of rain showers, flash flooding, and stormy conditions.

Mario is forecast to continue to slowly gain power as it roams the Pacific just south of Baja California Sur. Mexico will escape the worst of the impacts as Mario moves parallel to the coast on its journey to the northwest.

While Mario is expected to begin to lose wind intensity beginning on Wednesday, a great deal of moisture will remain intact as it inches closer to the U.S. coastline. This will translate to a higher chance of precipitation for Southern California and the Southwest.

Although California typically does not see the moisture associated with tropical weather systems, this is not the case for New Mexico and Arizona. These states are frequently in the line of fire for significant rainfall from tropical weather events that come ashore in northwestern Mexico. This happened most recently in early September when Hurricane Lorena formed in the same part of the basin that Mario is moving through. Lorena never made landfall in Mexico; however, its heavy rain bands were able to make it into Arizona, New Mexico, and Texas.

You have to go back to August of 2023 to find the last time that a tropical weather machine impacted Southern California. What was left of Hurricane Hilary moved into the Golden State, unleashing heavy rain and record-breaking flooding.

What to Expect This Week from Mario in the U.S.

A large zone of high pressure located to the west of the Rocky Mountains will drive the intensity of the rain that comes up from the Pacific this week. This strong area of high pressure is forecast to weaken in the days ahead. A weakening would allow more rain to filter up from the Pacific and into the southwestern U.S.

Conversely, only scattered rain showers and thunderstorms will make their way to the Southwest should the high-pressure zone remain high. The behavior of this high pressure will be something to keep an eye on as the week progresses. While any non-flooding rainfall will be welcome in most areas, the lightning produced by the storms could ignite new wildfires across the parched landscape.

Looking at a few specific metro area forecasts, San Diego is expected to see rain shower activity begin in the overnight hours on Wednesday. Rain will linger into Thursday morning before moving out in the afternoon. Temperatures will remain moderate in San Diego with highs in the upper 70s and lows that slide to about the 70-degree mark.

The rain will hold off until Thursday morning to the north in Los Angeles. The City of Angels will see another shot of rain during the overnight hours Thursday and into Friday. Highs will hover in the mid 80s during this time with lows forecast to land in the upper 60s.

It could be a rocky day of weather on Thursday in Palm Springs, California. The desert resort town is bracing for morning rain showers that evolve into scattered thunderstorms arriving in the afternoon. The mercury will still manage to climb into the low 90s during the peak afternoon heating hours. Overnight lows will bounce around in the mid 70s.

The moisture is forecast to make it to Las Vegas on Thursday evening. Some of these rain showers could turn into thunderstorms in the overnight hours. Highs in the mid 90s on Thursday will fall into the upper 80s on Friday.

You will find a similar situation in Phoenix with thunderstorms firing up under the cover of darkness. Those in the Valley of the Sun may want to make alternate plans on Friday with scattered rain showers and more storms in the forecast. Temperatures will cool from the triple digits earlier in the week to highs that top out in the mid 90s on Friday, thanks to the extensive cloud cover. Ovenright lows will remain toasty in Phoenix, bottoming out at about 80 degrees.

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