The end-of-winter storm series will continue this week across the Inland Empire, producing appreciable rain and snowfall, as well as windy conditions and possibly thunderstorms, according to the National Weather Service.
Forecasters said two “atmospheric rivers” will course over Southern California, the first arriving Tuesday and the second passing Wednesday night and Thursday.
“Showers could develop as early as Tuesday morning, with increasing chances of heavier rain in the afternoon and evening,” the NWS said in a statement. “For the Inland Empire, rainfall totals of .1 to .25 inches are possible, with the potential for locally higher totals if a heavier rainfall band develops. Snow levels will be 5,000 to 6,500 feet, with 1-2 inches of snow possible (in the San Bernardino Mountains).”
The Weather Service cautioned that “periods of gusty south winds are expected Tuesday, with peak gusts of 30 to 40 mph for the mountains and deserts.”
The first system will make a relatively fast exit to the east in the predawn hours Wednesday. However, its sequel will soon follow, anchoring over the region late Wednesday night.
The second upper level trough of low pressure “is expected to be colder than the Tuesday system,” the NWS stated.
“The cold nature of the storm aloft also increases the chances of thunderstorms across the area, leading to the potential of locally heavy rain and flooding,” the agency said. “The chances for exceeding 2 inches are 70 to 90% for the mountains and 40 to 50% for portions of the valleys. There is even a 30 to 50% chance of rainfall totals exceeding 4 inches of rain on the coastal slopes of the San Bernardino Mountains.”
Snow levels will initially hold above 6,000 feet, but drop to as low as 3,000 feet by Thursday night or Friday morning, when the disturbance spins eastward, according to meteorologists.
“Estimated snowfall totals above 6,500 feet are 8 to 12 inches, with locally up to 24 inches possible above 7,500 feet,” the NWS said.
Clear and mild conditions are forecast for the weekend.
High temperatures in the Riverside metropolitan area Monday will be in the mid 70s, but the mercury will barely exceed 60 on Tuesday, with lows in the upper 40s. From Wednesday to Friday, the daytime temps will peak in the upper 50s, falling into the low 40s at night.
In the Coachella Valley, the high will hit 80 Monday, but crest in the upper 60s Tuesday and Wednesday, maxing out in the low 60s Thursday and Friday. Lows will generally hover in the upper 40s to low 50s for the week.
The temperature band in the Temecula Valley will closely parallel Riverside metro, forecasters said.