A Santa Ana wind event will arrive before Santa Claus in the Inland Empire, with easterly gusts beginning Wednesday and continuing into Thursday, drying out the region and driving up wildfire danger, forecasters said Monday.
“Northeast winds of 15 to 25 mph with gusts to 40 mph or more will be howling below the mountains and wind-prone passes and canyons, reducing the relative humidity and setting up an extended period of elevated critical fire weather in mountains and inland valleys,” according to a National Weather Service statement.
A High Wind Warning was expected to be posted Monday or Tuesday.
The offshore flow will develop Wednesday morning and gain strength in the afternoon, meteorologists said. Winds will taper off in the overnight hours and start again Thursday, dying down just before Christmas morning, when coastal breezes are expected to return.
Humidity levels are predicted to drop into the single digits, creating tinderbox conditions for the region.
At the same time the Santa Anas are whipping the IE and other parts of Southern California, a “weird upper level low” pressure system will slide to the north, producing extensive cloud cover in the higher atmosphere, according to the NWS.
Christmas and the day after are slated to be calm and mild. However, in the transition to the final week of 2020, another trough will drop down from the Gulf of Alaska on the back of the jet stream, though the intensity of the system was uncertain.
“(Forecast) models have been pretty wide about whether it will be wet or dry Sunday and beyond,” according to the Weather Service. “There are a range of possibilities, from a little wet to very wet. The timing is homing in on Sunday night, and the precipitation could continue into Tuesday.”
High temperatures in the Riverside metropolitan area are expected to be in the low 70s from Tuesday to Saturday, with nighttime lows in the mid-40s. Nearly identical temps are forecast in the Coachella and Temecula valleys.