The storm producing torrential rain in coastal Southern California into Friday night will also threaten lives and property in the deserts of Arizona, California and Nevada this weekend.
In a sense, the rainfall will be like a fast-moving tropical system. A general 1 to 3 inches of rain will fall with locally higher amounts over the south-facing slopes of the mountains into Saturday night.
"Much of this rain may fall in a few hours' time, which is more than enough to cause significant runoff, flash and urban flooding due to the landscape in the region," according to AccuWeather Meteorologist Evan Duffey.
Flooding can occur in a matter of minutes in a situation like this. Arroyos can quickly fill with water.
Flash flooding will be a concern in the cities of Las Vegas; Palm Springs, California; and Phoenix and Yuma, Arizona.
Motorists traveling through this area should use caution. The heavy rainfall can also wash a significant amount of debris on the roads.
Due to the heavy rain and poor visibility, motorists will need to reduce their speed on highways such as interstates 8, 10, 15, 17 and 40. By slowing down during heavy rain, motorists can substantially reduce the threat of their vehicle hydroplaning. Braking action and traction are reduced in rainy conditions, especially where there is a mix of oil and water on the pavement.
During Friday night into Saturday morning, the heaviest rain will target southeastern California, southern Nevada and southwestern Arizona.
During Saturday, the threat for heavy rain and flooding will shift eastward across central Arizona before losing intensity over parts of New Mexico and western Texas.
The threat for flooding rainfall also includes part of northwestern Mexico into Saturday.
In addition to the likelihood of flooding rainfall, locally gusty thunderstorms can also affect the area.
"Snow levels will fall during the storm," according to AccuWeather Senior Meteorologist Brett Anderson. "Up to a few inches of snow will fall on Flagstaff, Arizona, with the bulk of the snow falling Saturday night."
Motorists should anticipate wintry travel along Interstate 40 during Saturday night with a rain and snow mix over the high ground at times during the day Saturday.
This storm will push seasonal rainfall to well above average for the region. Prior to the storm, rainfall in much of the region has been close to average.
Weather conditions will improve from west to east across the region as the weekend progresses. However, spotty showers can linger in some areas into Sunday.
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