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Heavy rains are expected to end L.A.'s long dry spell

Floods and FloodingAvalanches and LandslidesWildfiresNational Weather ServiceJet Propulsion LaboratoryColby FireDon Knabe

It's poor form to complain about rain, even a whole lot of it, when you really need it.

So Southern Californians will just have to grin and bear it beginning Wednesday night when the first of two major storms is forecast to move into the region.

The storms are expected to deliver the most rainfall since spring 2011. They come as Southern California and most of the state struggles through a historically dry stretch. Last year was the driest calendar year in L.A.'s recorded history. Since the beginning of the rain year in July, only 1.2 inches of rain has fallen in downtown L.A. Now it's going to rain — a lot — with more than four inches possible in some valley and foothill areas from the second storm.

"It's been almost three years since we've had rain like this," said Bill Patzert, a climatologist for the Jet Propulsion Laboratory in La Cañada Flintridge. "This is not a February or March miracle, but any rain is sweet because everything is so dry."

The possibility of so much rain in such a short period of time has firefighters, public works and law enforcement officials girding for the inevitable problems: traffic congestion, accidents and possible mudslides. "We haven't had weather in a while," said L.A. County Fire Department Inspector Tony Akins.

Although the rain is badly needed, it would take several seasons of above-normal rainfall to bust the drought gripping California.

The state has seen below-normal rainfall 11 of the last 15 years, making dry weather the norm over an extraordinarily long period, he said. Even if L.A. got two inches of rain from the coming storms, the city would still be only about 30% to 40% of normal for this time of the year.

Stuart Seto, a weather specialist for the National Weather Service in Oxnard, said the storm that hits the region Friday could linger through Monday, with the heaviest rain likely to fall Friday morning and afternoon.

The rain should help replenish some groundwater storage basins, bring temporary relief to desiccated foothill areas that are prone to wildfires and add snow to mountain areas. It'll also bring complications.

Law enforcement and fire officials expect an uptick in traffic accidents as the long-awaited rain mixes with accumulated oil on roadways to create extra-slick surfaces. The risk of vehicles hydroplaning and crashing increases under these conditions.

Like many agencies, the L.A. County Fire Department is keeping close tabs with the National Weather Service to determine staffing and strategy, Akins said.

"We're in constant communication with the National Weather Service as part of our routine operations," he said.

Akins said inmate crews at fire camps are prepared to respond to a variety of potential issues, such as mudslides, debris flows and flooding. Areas that have been razed by wildfires, such as the hills above Glendora, are especially vulnerable because fire renders the ground moisture averse, causing rainfall to rush downhill, rather than soak into the soil. Akins said fire stations will pass out sandbags to residents who need them.

Glendora City Manager Chris Jeffers said the city has a system to alert residents when they need to evacuate or take other actions. He said the city is in contact with weather and county fire officials, the L.A. County Flood Control District, the U.S. Forest Service, police and other agencies.

Jeffers said the Colby fire, which scorched nearly 2,000 acres last month, had "severely damaged" the hills above Glendora.

"The fire and severity are very reminiscent of the 1968 fires, which led to the horrific debris and mudflows in 1969," he said. "More damage was incurred to property as a result of the 1969 mudflows than the fire itself."

Jeffers said the forecasts don't suggest "substantial negative impact on the burn areas" from the first storm. But he said the city is more wary of the second round, which is expected to include thunderstorms.

"This is the storm that has us concerned at this point," Jeffers said.

He said that county flood control officials have helped the city survey residents in the burn area, visiting about 150 homes to offer advice on how to mitigate risks to their property. They have also visited about 60 residents who might need assistance in case of an evacuation order, Jeffers said.

Patzert of JPL said one of the problems that occur during heavy rains after prolonged dry spells is that storm sewers which haven't been flushed out can get overwhelmed. Some flooding is possible even in urban areas, he said.

With the rains coming, law enforcement officials are warning motorists to slow down on streets and freeways and to clean gutters. And county Supervisor Don Knabe reminded people that they also need to shut off their sprinkler systems.

"Your yard won't need to be watered until later next week," he said. "At the very least."

hector.becerra@latimes.com

ari.bloomekatz@latimes.com

ruben.vives@latimes.com

Copyright © 2014, Los Angeles Times
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Floods and FloodingAvalanches and LandslidesWildfiresNational Weather ServiceJet Propulsion LaboratoryColby FireDon Knabe
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