A nearly stationary storm will be slow to wring out all of its moisture over central and Southern California into the end of the week.
The storm has been pestering the region since the beginning of the week, bringing record-setting rainfall to some locales.
On Monday, Los Angeles and Lancaster, California, received more rain in 24 hours than they typically receive during the entire month of April. These cities joined Burbank and Palmdale, California, in setting new rainfall records for the date.
Downtown Los Angeles recorded 1.10 inches, breaking the old daily record of 0.84 of an inch from 1958. A total of 1.22 inches was measured at Los Angeles International Airport, topping the previous record of 0.87 of an inch from 1984.
Well over a foot of snow had already piled up across the high terrain of Southern California by Monday night.
— Mountain High (@mthigh) April 7, 2020
By Tuesday night, 72-hour rainfall totals were between 5-7 inches in the higher ground of Southern California and 1-3 inches in the lower elevations.
High precipitation amounts such as these are not typical for April as the frequency of storms moving in from the Pacific Ocean lessens during the month, on average.
The continued late-season rain and snow have greatly eased drought and water supply concerns heading into the dry season. The wet weather will also help people to follow guidelines from government and health officials and stay indoors amid the COVID-19 pandemic.
Into Friday, the greatest risk for rainfall heavy enough to trigger flash and urban flooding will be from San Diego north to Anaheim inland to Palm Springs.
Flash flood watches were in effect in these areas early Thursday morning.
Essential workers venturing out on the roadways are urged to use caution as pooling of water can lead to a heightened risk of hydroplaning while traveling at highway speeds.
Cars on the northbound Harbor Freeway (I-110) in downtown Los Angeles plow through deep water during a torrential downpour Monday, April 6, 2020. Snow and rain fell Monday on California as spring delivered the kind of stormy weather that was missing most of the winter. Numerous spinouts were reported on Los Angeles area freeways, and there were scattered reports of roadway flooding and canyon road rockfalls. (AP Photo/John Antczak)
It is possible that some secondary roadways are blocked by high water or debris from mud and rockslides.
Locally heavier showers will expand into portions of Nevada and Utah through Thursday. Temperatures will be as much as 10-20 degrees Fahrenheit below normal in places such as Phoenix and Las Vegas during this time.
Given the magnitude of the cold air at the core of this storm, small hail will be possible in any robust showers across the region.
Snow levels will dip to around 4,000 feet, bringing the potential for slippery travel along Interstate 5 near the Grapevine. Outside of stray snow showers on Thursday, the Sierra Nevada is largely done with accumulating snowfall from this storm.
Conditions are expected to fully dry out for Easter weekend as the storm finally shifts eastward.
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