Dangerous storm could also bring a mini-Miracle March to SLO County

The large storm system forecast to drop between 4 and 6 inches of rain on San Luis Obispo County by Thursday might tempt some to call this a Miracle March — but not so fast.

"I'd call this maybe a mini-Miracle March," said PG&E meteorologist John Lindsey on Tuesday afternoon. If San Luis Obispo receives about 5 inches of rain with this storm system as predicted, the city will reach a total of 13.15 inches of rain since July 1, 2017. The average total rainfall for San Luis Obispo at this time is 20.32 inches, Lindsey said.

If the models verify, that means SLO will be at about 65 percent of the normal average rainfall, Lindsey said.

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"It could rain more — we could get 7 inches — but we're just making an assumption that if we get 5 inches this is where it'll be," Lindsey said. "And there's no reason April can't be a wet month, too."

Compared to February, March has been an especially wet month for the area, Lindsey said. In February, Cal Poly recorded just 0.2 inches of rain.

"February was pretty disappointing," Lindsey said.

March has seen a series of low-pressure systems move into the area, bringing a decent amount of rainfall. Average rainfall for March in San Luis Obispo is about 3.37 inches, Lindsey said. So far this March, Camp San Luis Obispo has received 3.7 inches and has reported 3.99 inches, Lindsey said.

With this storm, a low-pressure system is tapping into a large plume of subtropical moisture to create an “atmospheric river,” which will cause moderate to heavy rain Tuesday afternoon through Thursday.

The heaviest rain in SLO County is expected to occur Wednesday night into Thursday morning. Rain showers will continue Friday into Sunday, with mostly clear and dry weather returning Monday through next Wednesday, Lindsey said.

"If we came off a drought, I'd probably call it a total Miracle March, but since we're coming off such a wet year last year, I'll call this a mini-Miracle March," he said.

The "Miracle March" sentiment would ring truer in Santa Barbara County, where the area never made it out of the drought the way SLO County did, Lindsey said.

However, "I don't want to call it a miracle because it would be disastrous for the burn areas," Lindsey said. "It would be a miracle for northern Santa Barbara County but kind of a nightmare down south."

Horses stand in deep greenery at Cal Poly as the first day of spring arrives on Tuesday. David Middlecamp

Officials in Santa Barbara County have ordered mandatory evacuations for communities below last year's wildfire burn areas. The order went into effect at noon Tuesday.

"This is a life-threatening storm," read a tweet from Santa Barbara County on Tuesday afternoon. "Forecast shows the storm has not diminished and is projected to produce prolonged rain that may trigger debris flows."

According to another tweet from Santa Barbara County, the majority of residents in mandatory evacuation zones have left the area.

On Tuesday afternoon, Cal Poly's Department of Emergency Management said it was monitoring a hillside area that experienced a slide in February 2017 as well as a separate hillside area burned by a brush fire in September.

The hillside that experienced the slide has been monitored continuously and, through last summer, university officials have cleaned up the area, graded the land and made drainage improvements. The slide caused nearby Fremont Hall to close, and the dorm remains closed, the university said.

The hillside that experienced the fire has been re-seeded and "has demonstrated no movements during recent storms," the university said. "The university has determined through soil mapping that there is not a significant risk of a landslide in the burn area."

In advance of the storm, university officials ask that Cal Poly students, faculty and staff have an up-to-date cellphone number registered by logging into and clicking the "Personal Info" tab. Community members without a Cal Poly email account can register for university alerts by texting "Join CalPoly" to 30890, the university said.

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