A fire danger warning in Southern California. Photo by Chris Jennewein.

Sunday is the calm before Santa Ana winds, combined with low humidity, will result in critical fire weather conditions Monday and Tuesday, according to the National Weather Service.

Mid and high-level moisture will increase Sunday night and Monday as an upper trough over Oregon digs south across California before stalling off the coast of northern Baja Monday night, forecasters said.

“This moisture will translate into mid and high-level clouds, but relative humidity increases will be modest and not too significant,” the NWS said.

High temperatures on Monday were expected to reach 64 to 69 near the coast, 71 inland, 71 to 76 in the valleys, 56 to 64 in the mountains and around 73 in the desert.

Winds are predicted to pick up in the northern areas very early Monday morning, then spread into southern areas by Monday afternoon, NWS said.

Peak wind gusts will generally range from about 40 to 50 mph, but some gusts to 60 mph could occur in the windiest locations.

The strongest winds will likely be late Monday night into Tuesday morning, according to the agency.

Although this Santa Ana event looks to be weaker than the last, forecasters said winds will be quite widespread, reaching into the Inland Empire, inland Orange County, and the San Diego valleys.

Even inland coastal areas could get some breezy offshore winds, meteorologists said.

A Red Flag Warning is in effect from early Monday morning through Tuesday evening for the mountains, valleys, and passes.

Humidity will continue to be below 15 percent for Monday and Tuesday, according to NWS.

Monday will be cooler in the deserts, mountains and inland valleys as the surge of cold air moves in from the north.

Tuesday and Wednesday will be warmer, especially west of the mountains with downslope
warming raising temperatures into the 80s in some spots, the NWS said.

Onshore flow will briefly return for Thursday and Friday, bringing cooler temperatures and higher coastal humidity inland.

These conditions will not last long as models show the area possibly going back into another Santa Ana pattern sometime next weekend, although forecasters said exact details on this event are uncertain at this time.

Updated 7:15 a.m. Dec. 7, 2020

— Staff and wire reports

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