Prepare to get wet.
After months of dry weather, some with record-breaking heat, the first major storm of the season is expected to barrel into Stockton starting Tuesday night.
On Wednesday, chances of rain are 80%, the National Weather Service reports.
The storm will come in two batches. The first will strike over the next couple of days, followed by off-and-on showers. Then comes another significant drenching over the weekend, NWS meteorologist Sara Purdue said.
The first round could produce a half-inch to an inch of rain through Friday. The second will bring up to another inch. Showers will be sporadic into early next week, the National Weather Service predicts.
The heaviest rain in the early part of the storm will be centered closer to Sacramento, well north of Stockton, Purdue said. But over the weekend, a low-pressure system will shift and bring more widespread rain across the valley, she said.
Heavy rain and winds are expected elsewhere in Northern California.
The National Oceanic and Atmospheric Administration’s Weather Prediction Center issued excessive rainfall risks beginning Tuesday and lasting through Friday as the strongest atmospheric river — long plumes of moisture stretching far over the Pacific Ocean — that California and the Pacific Northwest has seen this season bears down on the region.
The storm system has intensified so quickly that it is considered a “bomb cyclone,” explained Richard Bann, a meteorologist with the Weather Prediction Center.
The areas that could see particularly severe rainfall will likely stretch from south of Portland, Oregon, to north of the San Francisco area, Bann said.
“Be aware of the risk of flash flooding at lower elevations and winter storms at higher elevations. This is going to be an impactful event,” he said.
What is a bomb cyclone?
Bomb cyclone is a term used by weather enthusiasts to describe a process that meteorologists usually call bombogenesis. It’s the rapid intensification of a cyclone in a short period of time, and it can happen during powerful storms.
The weather phenomenon occurs during the rapid intensification of a cyclone located between the tropics and the polar regions, according to the National Oceanic and Atmospheric Administration. It can happen when a cold air mass collides with a warm air mass, which is something that can occur over ocean waters, the agency says.
The measurement needed to determine whether a cyclone can be classified a bomb cyclone can be tricky, but it largely concerns a swift drop in pressure. Atmospheric pressure is measured in millibars by the National Weather Service. If a storm decreases 24 millibars or more in 24 hours or less, it can be considered a bomb cyclone, said Stephen Baron, a forecaster with the weather service in Gray, Maine.
“I would say rapid intensification of hurricanes is one of the more common times we see it,” Baron said. “We do see it with Nor’easters occasionally.”
The atmospheric river storm that is approaching Northern California and the Pacific Northwest intensified swiftly enough that it’s considered a bomb cyclone, the National Weather Service’s Weather Prediction Center said.
— The Associated Press
In Northern California, flood and high wind watches go into effect Tuesday, with up to 8 inches of rain predicted for parts of the San Francisco Bay Area, North Coast and Sacramento Valley.
The storm should be good news for skiers and snowboarders, though. Purdue said there’s a 20% to 60% chance it could drop up to a foot of snow in parts of the Sierra Nevada.
But a winter storm watch has been issued for the northern Sierra above 3,500 feet, where up to 15 inches of snow is possible over two days. Wind gusts could top 75 mph in mountain areas, forecasters said.
“Numerous flash floods, hazardous travel, power outages and tree damage can be expected as the storm reaches max intensity” on Wednesday, the Weather Prediction Center warned.
After a summer of record heat in Stockton, the rain could come as a welcome relief for many, especially farmers and backyard gardeners.
Since California’s water year began Oct. 1, Stockton has already recorded about a third of an inch of rain.
If this prolonged storm’s rain totals come through as predicted, Stockton could be on track for a good to better-than-average water year. Average rain totals for the 30 years through 2020 have been 1.4 inches in November, Purdue said.
The Associated Press contributed to this report.