A final round of precipitation, possibly the heaviest of the week, is expected in the Inland Empire Thursday, raising the risk of flash flooding throughout the region as well as dangerous mud slides and debris flows for numerous communities in the Holy Fire burn area.
The National Weather Service issued a flash flood watch for the Riverside County mountains and valleys through Thursday afternoon.
“The greatest threat for flash flooding (in Riverside County) would be between 8 a.m. and 5 p.m. Thursday,” according to a National Weather Service statement. “With the heaviest rain still to come on top of recent rainfall already soaking the ground, urban flooding is likely and flash flooding is certainly possible anywhere within the watch area.”
As of 9 p.m. Wednesday, the storm systems over the past four days had dropped 1.25 inches of rain at the Riverside Municipal Airport, 1.34 inches in Temecula, 2.72 inches in Lake Elsinore, 4.92 inches near upper Horsethief Canyon, 1.22 inches in Beaumont and .91 of an inch at the Palm Springs International Airport, according to the NWS.
Up to three-quarters of an inch of rain is forecast Thursday for the Riverside metropolitan area with around six-tenths of an inch predicted in Lake Elsinore, forecasters said. The San Gorgonio Pass near Banning could see up to eight-tenths of an inch of rain and the Coachella Valley is expected to get around one-tenth of an inch.
Snow levels are expected to remain above 8,500 feet.
The Riverside County Emergency Management Department maintained voluntary evacuation warnings for neighborhoods throughout the Temescal Valley and just north and west of Lake Elsinore, including Amorose, Alberhill, Glen Ivy, Glen Eden, Grace, Horsethief Canyon, Maitri, McVicker, Rice and Withrow.
The agency added the Alvarado and Laguna “B” zones to the evacuation warning list Wednesday afternoon, based on the prospect of major runoff, mud and debris flows.
A mandatory evacuation order was issued for the Laguna “A” zone.
Each impacted community lies along the eastern boundary of the national forest, where the 23,000-acre Holy Fire in August denuded steep terrain below Santiago Peak, permitting water to flow unchecked onto lower slopes where subdivisions are situated.
More information is available at www.rivcoready.org.
Rains on Dec. 6 resulted in significant flooding and mud flows into several neighborhoods, prompting street closures and evacuations. However, there was no major damage to homes.
The NWS also issued a wind advisory for the county mountains and the San Gorgonio Pass near Banning that is set to last from 7 a.m. Thursday through 7 a.m. Friday.
The final storm system is expected to leave the region by Thursday evening and dry weather with warmer temperatures will prevail from Friday afternoon through next week, forecasters said.