Forecasters say flash flooding is likely in the area from Friday to Sunday. The interior mountains of Southern California could see up to 5 inches of rain, an extraordinary amount. “Confidence remains high for a significant precipitation event in this region,” the National Weather Service said in an online discussion Thursday. The remnants of the storm could also bring gusty winds and dangerous surf conditions to coastal areas of Southern California. A Category 1 hurricane with sustained winds of 85 mph, Kay is expected to make landfall on the west-central coast of Baja California in Mexico on Thursday afternoon. The storm is weakening and is forecast to downgrade to a tropical storm on Friday. Kay, responsible for at least three deaths in Baja California, is still a major rain producer. The storm is expected to bring 6 to 10 inches of rain across much of the peninsula, with local amounts of up to 15 inches. Near the coast, Cay is expected to whip up large waves and dangerous rip currents, with a damaging storm surge or rising ocean water over normal dry land also possible. Tropical storm warnings have been posted along the entire Baja California coastline, including on its eastern side, which sits on the Gulf of California. This is because Kay is a major hurricane. Tropical storm force winds (39+ mph) extend up to 230 miles from its center, while hurricane force winds (74+ mph) extend 35 miles from the center.
Implications in the Southwestern United States Kay is expected to weaken further and bend away from the Mexican coast as it approaches parched Southern California. However, winds from the southwest will carry Kay’s moisture into the region, bringing first clouds that will help end the prolonged, record-breaking heat wave. The driest, the wettest, the hottest: Sacramento’s unsettling sizzle The remnants of the hurricane will also carry unusual amounts of moisture that could help improve Southern California’s ongoing drought. Some storms associated with Kay have already begun rumbling near Riverside, California, bringing isolated heavy rain and lightning. Although the rain is needed, the National Weather Service warns that Kay’s arrival will not be without risks. “Despite these positives, it’s never good to get rain all at once, a feature very common in slow-moving tropical storms,” the Weather Service wrote. Hurricanes move more slowly – which makes them even more dangerous Precipitable water, a measure of atmospheric moisture, is forecast to be more than 2 inches in parts of Southern California by late Friday. That’s five standard deviations above the norm for the area this time of year, meaning it’s very rare. Flash flooding is most likely in narrow canyons, in urban areas such as San Diego, Palm Springs, Calif., and Yuma, Ariz., and over burn scars, where fire has removed vegetation and water tends to it runs fast instead of soaking the ground. Flood watches have been lifted from central Southern California to western Arizona, and the Weather Service has placed a large swath of Southern California and a growing portion of southwestern Arizona in the light to moderate danger zone for flash flooding from Friday through Saturday morning. Rainfall amounts in excess of 2 inches are possible in the flood watch area, with up to 4 or 5 inches possible on the eastern slopes of the mountains, where easterly winds will intensify the precipitation. Updated rainfall potential through Sunday from moisture from Tropical Cyclone Kay. The highest chance for heavy rain and flash flooding is for the eastern slopes of the mountains and adjacent desert areas for Friday afternoon and evening. #cawx pic.twitter.com/JzaWihbf2k — NWS San Diego (@NWSSanDiego) September 8, 2022 In San Diego, an inch or less of rain is expected, mostly Friday through Saturday morning. But being along the coast will bring a separate set of risks. The Weather Service is warning of dangerous rip currents and raised surf of 3 to 6 feet, along with the possibility of gusty winds of up to 40 mph. In Los Angeles, the Weather Service is predicting 0.25 to 0.75 inches of rain, with 1 to 2 inches in the mountains to its east, mostly Friday night into Saturday. Some beneficial rain could reach as far south as the San Joaquin Valley before the precipitation fades Sunday. Although Kay will not come close to reaching California, it will still bring strong winds on Friday that will increase local fire danger. Gusts in the Laguna Mountains east of San Diego could exceed 70 mph, which will help fuel any flames. The storms could also bring dangerous cloud-to-ground lightning that could spark wildfires in the region — though any rain from Kay may help extinguish some of them. Kay is not the first tropical system to affect California, but such occurrences in the state are quite rare. They usually come from the remnants of tropical storms and hurricanes, as with Kay, rather than direct hits. No named system has ever reached California, although an unnamed storm in 1939 crossed the coast around Long Beach, bringing tropical storm conditions. California’s most notable encounter with a tropical system was probably in 1976 when Tropical Storm Kathleen, previously a hurricane over the ocean, entered south-central California from Mexico. Kathleen unleashed a maximum rainfall of nearly 15 inches, a state record. The storm caused severe damage in Ocotillo, California and was blamed for 12 deaths in the United States. Jason Samenow contributed to this report.
