Priscilla Expected to Bring Heavy Rain to the Southwest United States

Hurricane Priscilla was a Category 2 storm on Tuesday, with winds in excess of 100 miles per hour as it moved north just off the coast of Mexico. Although it was expected to weaken in the coming days, forecasters said a surge of moisture from the storm was likely to create the potential for heavy rainfall over the Southwest United States later this week.

Here’s what you need to know:

Through Wednesday, tropical storm conditions were expected for the coastline of Baja California from Cabo San Lucas to Cabo San Lazaro, Mexico, where a tropical storm watch was in effect.
As the storm weakens, it is expected to interact with another system far to the north, which will push subtropical moisture from the hurricane far inland across the West this week.
Forecasters warned that the storm systems could drop several rounds of rain as far away as Las Vegas.

What’s expected in Mexico:

Heavy rainfall is expected to have an impact on portions of southern Baja California Sur, which could result in flash flooding, particularly over higher terrain. Up to two inches of rain is expected, with local totals up to four inches.
Swells generated by Priscilla are affecting parts of the coast of southwestern and west-central Mexico, as well as the coast of the southern Baja California peninsula, which are likely to cause life-threatening surf and rip current conditions.
As a preventative measure, the government of Baja California Sur announced the cancellation of classes at all educational centers there, starting Tuesday in Los Cabos and La Paz. A dozen shelters were also set up in Los Cabos for people at risk in the area.

What that means for the southwestern United States:

Priscilla is expected to weaken on Wednesday. However, forecasters said, as a different large storm system moves inland from the Pacific Northwest and spreads over the Western United States, it will pull in tropical moisture from Priscilla. This interaction is expected to bring periods of moderate to heavy rainfall across parts of the Southwest from Thursday through the weekend.

Chances for showers and thunderstorms are expected to begin on Thursday. The Weather Prediction Center has highlighted parts of Southern California, Arizona, Nevada, Utah, Colorado and New Mexico, including Phoenix and Las Vegas, for being at some risk of flash flooding through Friday. Forecasters said the “dramatic increase” of moisture in the region would likely lead to several rounds of rain.
The San Diego office of the Weather Service said tropical moisture from Priscilla was expected to peak there on Friday, with “measurable rainfall” greatest for the San Diego County mountains, where one inch or more of rain was expected. The risk of flash flooding will diminish through the weekend, though the office said some showers and thunderstorms could still occur near the mountains on Saturday.
Beginning Friday and continuing through the weekend, Arizona, Utah and Colorado remain in danger of flash flooding, and the risk shifts farther east into New Mexico. The Weather Prediction Center has highlighted a Level 2 out of 4 risk for some areas, including Flagstaff, Ariz., through Sunday. Late last month, three people were swept away when intense rainfall led to flash flooding in eastern Arizona.
Though showers and thunderstorms are expected to develop across the Desert Southwest starting on Thursday, the Las Vegas office of the Weather Service said “the best and most widespread precipitation chances” there were likely to arrive on Friday. The heaviest downpours are likely to occur in northwest Arizona, where one to two inches of rain may fall across southern and eastern Mohave County.
The Flagstaff office of the Weather Service said tropical moisture from Priscilla would bring “an increasing potential for heavy rainfall and localized flooding” for Northern Arizona, especially late Friday into Saturday. Two to four inches of rain was expected, though forecasters noted the exact area for the heaviest rainfall remained uncertain, with weather models differing on whether it would focus over western, central or eastern Arizona instead.