California and Southwest Brace for Rain Leftover From Mario

The remnants of the former Tropical Storm Mario will help to put a dent in the ongoing dryness across California and the Desert Southwest. However, the sudden influx of tropical moisture will also spell trouble in the form of the threat of flash flooding and debris flows. Here is a look at the unsettled pattern headed toward this part of the country this week.

Leftover Moisture from Tropical Storm Mario Headed into California and the Southwest

What is left of Tropical Storm Mario is now moving to the northeast and into California and the Southwest to close out the work week. Although the parched region will welcome the rain, too much precipitation too quickly will raise the risk of flooding and other dangers. In addition, the frequent lightning strikes associated with this weather maker will also present concerns of new wildfires igniting.

The majority of the rain for the Interstate 5 corridor through Southern California will fall on Thursday morning. For example, Los Angeles is forecast to wake up to more rain after a soaker of a night on Wednesday. Conditions are expected to clear briefly in the City of Angels on Thursday afternoon before another round of rain moves in during the overnight hours. Locally heavy rainfall is possible after the sun goes down.

Widespread rainfall amounts of about 0.50 of an inch to 1 inch are on tap for the region. This is well over the historical average amount of precipitation for the month of September.

The lack of rain lately in this part of the Golden State will mean that the new rainfall will mix with oil on the road to generate slick surfaces. The runoff produced by the moisture will trigger ponding on roadways and the chance of debris flows across the hilly terrain.

The line of moisture could creep as far north as San Francisco. The greatest chance of rain in the Bay Area will be Thursday evening and overnight. It will be a cool day with highs that struggle to reach the 70-degree mark and winds out of the west-southwest at 10 to 20 mph. To the east, you cannot rule out the chance of a thunderstorm in California's Central Valley.

The heaviest rain will fall over the south- and west-facing mountains in Southern California. Up to 2 inches of rain is possible in this zone. Moving into the Southwest, the major metro areas of Phoenix and Las Vegas will also be under the gun for flash flooding and debris flows during the peak of the activity. Lastly, portions of the Sierra Nevada could also experience some of these same threats.