Wet Christmas Week Expected Across Southern California

Southern California is in for a wet Christmas week, with four days of rain expected to begin Tuesday, forecasters said Monday.

A flood watch was issued for Tuesday afternoon through Wednesday evening for much of Los Angeles County, with mud and debris flows possible across foothill and mountain areas, including recent burn scars, according to the National Weather Service.

The agency is also predicting “very strong winds” Tuesday night and Wednesday, with gusts up to 80 mph over the higher peaks in the mountains, and up to 40-50 mph across lower elevations.

The NWS said an “Atmospheric River that has been pointed towards northern California the last few days will shift south and take aim at SoCal” on Tuesday, with less than a half-inch of rain expected Tuesday evening before the heaviest part of the storm occurs after midnight Tuesday night into Wednesday.

“Hourly rain rates, especially in the upslope areas, should easily top one inch per hour during the peak of the storm on Wednesday,” the NWS said. “The heaviest rain will be in the south-facing mountains, but very heavy rain, possibly close to an inch per hour, is possible at lower elevations as well and anyone in particularly vulnerable areas … or any recent burn scars should start taking protective actions ASAP.

“There will almost certainly be numerous mudslides, severe flooding either from heavy rain or clogged storm drains, and possibly debris flows near recent burn scars,” forecasters continued.

While the worst of the storm will likely be Wednesday, periods of rain, possibly heavy at times, are expected on Christmas Day. Moist south to southwest flow will continue to usher in sporadic showers to the area Friday and Saturday, though rain amounts by that time should be under a quarter inch per hour.

Snow is not expected to be a major factor with this event, with levels dropping to around 7,000 feet Thursday and Friday.

A cooling trend will arrive ahead of the storm, with Monday’s high temperature expected to reach 67 degrees in downtown Los Angeles, then decrease gradually to 59 on Friday. Overnight lows will generally be in the 50s for the beginning of the week, then drop into the 40s in some areas later in the week.