A cooling trend and increasing onshore winds were expected to help firefighters battle several Southern California wildfires — though forecasters warned that breezy conditions in inland and mountain areas could still create some concerns.
A marine layer was to bring cooler temperatures, higher humidity and increasing night and morning cloud cover through the weekend.
“Wednesday through the weekend there will be more westerly winds, which will bring in higher humidity and better (firefighting) conditions,” NWS meteorologist Adam Roser said.
In the Inland Empire, where the Bain and Verona fires were burning, temperatures were likely to remain warmer but gradually ease into the weekend.
Highs, in the mid- to upper-80s through the end of the weekdays, will likely cool a few degrees over the weekend and into next week. Afternoon and evening west winds, though, are expected to increase across inland valleys, mountains and passes, with gusts of 15 to 20 mph.
In Los Angeles and Ventura counties, conditions are expected to become cooler and more humid through the weekend as onshore flow strengthens.
“Today is going to be the warmest day for the rest of the week,” Weather Service meteorologist Bryan Lewis said on Wednesday, May 20, adding that inland temperatures that reached around 90 degrees Wednesday are expected to drop into the mid-80s by the weekend.
Coastal and valley areas in Los Angeles and Ventura counties were expected to see increasing night and morning low clouds and fog, with temperatures cooling closer to seasonal averages.
Lewis said the last few mornings brought breezy offshore winds, which can worsen fire behavior, but forecasters do not expect those conditions to continue in the coming days.
Instead, onshore winds are expected to increase each afternoon, helping cool temperatures and raise humidity levels across Los Angeles and Ventura counties.
“Offshore winds can ramp up fire activity,” Lewis said. “Onshore winds can too, but they also help bring cooler temperatures and higher humidity.”
Forecasters said the stronger onshore flow should improve firefighting conditions overall, though gusty winds and dry vegetation could still help spread a fire.
Orange County is expected to see a steady cooling trend into next week as marine air pushes farther inland. Roser said temperatures should generally remain in the 70s through Friday before dropping into the 60s in many areas next week. Coastal cloud cover and morning fog are also expected to become more widespread.
