Heavy rain appears to be on the way for Christmas Eve and Christmas Day across the Inland Empire, according to the National Weather Service.
The agency stated an atmospheric river — in wintertime dubbed a “Pineapple Express” — drawing moisture from the Pacific will combine with a trough of low pressure dropping out of the Gulf of Alaska to fuel moderate to heavy precipitation throughout the region, beginning Tuesday night or Wednesday morning.
“Models suggest Wednesday as the period of the heaviest rain, as the atmospheric river moves through the area from north to south, with additional lighter showers expected on Christmas Day,” the Weather Service said in a statement.
Forecasters anticipated upwards of 1 inch of rain in the Riverside metropolitan area and surrounding valleys, with higher amounts in the mountains.
“This will lead to an increased debris flow and flooding risk across all areas,” the NWS stated. “Confidence continues to increase that snow levels will be high, mainly above 8,000 feet for the first part of the storm system through early Thursday.”
No winter weather advisories, flood advisories or other alerts had been issued as of this week.
Temperatures were forecast to drop with the approach of the storm system, but not dramatically.
For the remainder of this week, the mercury was forecast to remain unseasonably elevated in the Riverside area, with daytime highs from Thursday to Sunday hovering in the upper 70s to low 80s and overnight lows in the low 50s. However, beginning Tuesday, temperatures will start to moderate, peaking in the upper 60s, with lows around 50.
In the Coachella Valley, highs are likely to top out in the low to mid-80s for the remainder of the week and weekend, with lows in the upper 50s. That temperature band will hold until early next week, when the mercury will fall 10 degrees from current levels to Christmas, meteorologists said.
For the Temecula Valley, highs for the remainder of this week will generally peak in the mid 70s, dropping to the mid-40s overnight. Daytime temps will give way to cooling starting Tuesday, with the mercury settling just below 70, and lows in the low 40s, to Christmas.
The NWS said another storm system appears to be taking shape in the Pacific Northwest, with a possible track into Southern California soon after Christmas, though the exact timing and strength were still undetermined.