Tropical Storm Rachel has prompted rare watches in Southern California, and is forecast to sweep into the Southwest bringing flooding rain, strong wind gusts and enhancing coastal flooding to cities like San Diego and Las Vegas.

That's just one of the interesting weather stories we'll see in the days ahead, including northern Rockies snow and Hurricane Simon raking southwest Mexico, including Puerto Vallarta.

First, Rachel

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A tropical storm watch has been issued in parts of Southern California ahead of Rachel.

Specifically, that watch includes San Diego County and also extends westward to San Clemente Island off the San Diego County coast.

This means tropical storm force winds (in this case, mainly in gusts) are possible within 48 hours.

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It's the first tropical storm watch issued anywhere in Southern California since the remnant of former Hurricane Hilary moved into the state in 2023. (Note: while a Southern California tropical storm watch was issued in 2023, Hilary never made it to California as a tropical storm, according to a National Hurricane Center post-storm analysis.)

Tropical storm warnings have also been issued for the northern part of Baja California, where the chance of 40 mph winds are much higher.

The forecast

Rachel is tenaciously hanging on despite few thunderstorms near its center.

Since it is forecasted to both track over record warm ocean water for this time of year and get a boost of thunderstorms from an approaching jet stream. Rachel could maintain tropical storm status until its Saturday night landfall in the northern Baja Peninsula, then possibly even into parts of the lower deserts of southeast California early Sunday.

This could mean strong wind gusts and some enhanced coastal flooding in parts of Southern California Sunday. These gusty winds could also spread into much of the Southwest Sunday.

As the remnant moisture moves into the Southwest on Sunday, heavy rain could bring flash flooding across the region, including Southern California, lingering into Monday or Tuesday.

Widespread rain totals of 1 to 3 inches are expected with locally higher amounts possible. This could lead to flash flooding of normally dry creeks, arroyos, slot canyons and urban areas, including parts of the L.A. Basin, San Diego metro, Las Vegas and Salt Lake City.

(MORE: What to do before, during and after a flood)

Wait – is that snow on the map?

Yes, as the moisture from Rachel meets colder air from a front moving in from the Northwest, snow could accumulate in parts of the Sierra Nevada as well as the Rocky Mountains.

Parts of Wyoming, Montana and Idaho could see their first significant snow of the season, with some places forecast to get over a foot.

(MORE: The West's best shot at snowpack recovery is from El Niño)

Much-needed heat relief

As that front collides with the tropical moisture, it will also bring a long-awaited cooldown to parts of the Southwest, including Los Angeles.

After being stuck in the 90s and triple digits for over a week, temperatures will drop 5 to 15 degrees below average for much of the region by Monday.

Highs will be in the upper 60s and 70s for Southern California, while parts of Arizona and New Mexico will drop into the 70s and 80s.

Hurricane Simon

As all this is happening, a powerhouse hurricane is taking aim on southwestern Mexico.

Hurricane Simon will slam into Mexico's Jalisco state Sunday, then track toward the north-northwest, bringing its core over or near Puerto Vallarta later Sunday.

Damaging winds and flooding rain are both likely along and near the track of Simon in southwest Mexico. Up to 25 inches of rain could lead to dangerous landslides in hilly or mountainous terrain.

This could be the strongest, most damaging hurricane to affect Puerto Vallarta in three years, since Hurricane Lidia downed numerous trees, damaged roofs and triggered landslides in and around the city in October 2023.

It's uncertain whether any of Simon's remnant moisture or spin will make it into parts of the Southwest or Plains in the week ahead.

(MORE: What a historic El Niño means for your fall and winter)

Caitlin Kaiser graduated from the Georgia Institute of Technology with both an undergraduate and graduate degree in Earth and Atmospheric Sciences before starting her career as a digital meteorologist with weather.com.