One of the fiercest storm systems so far this season is expected to peak this afternoon, bringing rain and gusty winds to parts of Southern California and snow to the mountains while prompting worries about flooding and possibly playing havoc with travel as Election Day voters head to the polls.

The three-day storm moving south from the Gulf of Alaska brought some rain during the day Monday but was expected to intensify later in the evening, with forecasters predicting the heaviest rainfall in Southern California this afternoon. The wet weather is likely to linger into Wednesday before tapering off.

Total rainfall from the storm could exceed 5 inches in some areas, according to the National Weather Service’s Los Angeles office.

“Periods of rain, mountain snow and strong and gusty winds will affect the area through Wednesday as a significant storm system originating out of the Gulf of Alaska moves over the region,” according to the NWS.

In the mountains, snow accumulation was possible Monday night at 6,500 to 7,000 feet, where forecasters predicted 6 to 12 inches, with local amounts up to 20 inches.

Wind gusts in the mountains and high desert could reach 55 mph today, forecasters said. The weather service advised motorists to “prepare for slick roads and wintry travel in the mountains,” as well as potential issues along the Grapevine today.

On Monday, the city of Duarte issued mandatory evacuations for about 25 homes in the Fish fire impact area from 11 p.m. Monday night through today, and potentially Wednesday.

In Orange County, sheriff’s officials issued a voluntary evacuation order for Silverado Canyon, Williams Canyon and Modjeska in the Bond fire burn scar area from 4-7 p.m. today. Orange County election officials also announced the closure of a voting center Monday afternoon in the area after the warning was issued. An evacuation center also was made available today at the Normal P. Murray Community and Senior Center in Mission Viejo, along with the offer of overnight shelter.

In Monrovia city officials warned residents of possible debris and mud flow in the Oakglade Drive and Ridgeside Drive neighborhoods and offered some pre-filled gravel bags to residents in need.

With heavy downpours and the possibility of flooding in some locations predicted today, the Riverside County Fire Department on Monday offered free empty sandbags to residents at most fire stations countywide.

One lane on the northbound 15 Freeway in Hesperia from Oak Hill Road to Ranchero Road was closed because of flooding Monday afternoon.

The San Bernardino County mountains are expected to see 3 to 6 inches, with some of the highest peaks seeing 7 to 8 inches or above this afternoon and evening. Snow levels are expected to be high, above 7,000 feet, but will decrease slightly tonight to above 6,000 feet, National Weather Service meteorologist Samantha Connolly said.

Riverside County mountains will see slightly less rainfall — estimated to be about 2 to 3 inches total. San Jacinto Mountain, which is over 10,000 feet of elevation, could see 1 to 2 feet of snow.

Coastal Orange County will see 1 to 1.5 inches with the Santa Ana Mountains expected to receive slightly more rain, around 2 to 4 inches.

The brunt of the storm will also hit Los Angeles County today. Coastal and valley regions are expected to see a total of 1 to 1.75 inches across the three days.

Most areas across the region will also be windy today.

By Wednesday afternoon, most of the rain and wind will have passed. Temperatures will remain below seasonal normal, but a gradual warmup and drier weather is predicted Thursday onward.

This storm is one of the more significant systems forecasters have seen at the beginning of this rain season, but the state will need many more storms of this intensity in the long term to help with the drought, Connolly said.

“Any rain we can get will help in the short-term,” he said.

City News Service contributed to this report.