Siberian Chill Delivers Snowy Shock to County

Damaging freezes were predicted by early today for San Diego County strawberry and avocado growers as near-record low temperatures swept through Southern California in the wake of a bitter-cold Siberian air mass that sprinkled coastal areas with brief snow flurries Wednesday morning.

The cold air accompanied a weather front that brought gusty winds and unusual flakes of snow to normally balmy coastal and inland valley areas across the county. Traces of snow were officially recorded at Poway, Ramona, Santee and Alpine, and brief flurries even surprised early-morning commuters in Encinitas and Del Mar. San Diego reported a trace of rain.

Some agricultural damage would be inevitable from the cold predicted for both overnight and for early Thursday morning, Wilbur Shigehara, meteorologist-in-charge of the National Weather Service in San Diego, said Wednesday.

Shigehara predicted that inland temperatures would plummet to 21 degrees or lower at Bonsall early today, where much of the county’s $21-million annual strawberry crop is now grown. Wednesday night would be the coldest of the year, Shigehara said, with the temperatures hovering at the point where he issued a rare freeze warning Wednesday night.

County agricultural officials predicted “only a light sleep” for most growers because frost alarms would probably sound by midnight as temperatures dipped below the freezing mark, along with clearing skies and calm winds.

Emergency shelters for the homeless opened Wednesday night at National Guard armories in Vista and El Cajon because overnight temperatures in inland suburban locations were forecast to be in the low 30s or upper 20s. Donna Palmer of County Disaster Preparedness Office said the shelters would remain open until 7 a.m. today, then probably reopen at 7 p.m.

The city of San Diego’s emergency shelter at the Balboa Park Municipal Gym was not opened Wednesday night because forecasters predicted the overnight low in the city proper would dip to 37. That is 2 degrees above what city Office of Emergency Management officer Pat Sutton said is the threshold for declaring a cold emergency.

Existing homeless shelters throughout downtown, including the Salvation Army and St. Vincent de Paul, did agree to take in more homeless than usual overnight because of the cold, Sutton said.

The cold Wednesday came as no surprise to Shigehara and his colleagues, who had been tracking the Siberian cold air mass since Friday, when it began to move southeast across Alaska and into the Western United States.

“We actually began putting out warnings to growers over the weekend,” Shigehara said.

The only measurable snow was at Mt. Laguna, where 4 inches fell as the temperature reached a high of only 34 degrees, after a low Wednesday morning of 16, with a wind chill of minus 25 degrees because of 25 m.p.h. winds gusting in the Cuyamaca area. (The National Weather Service computes wind-chill temperatures when the air temperature is below 35 degrees and accompanied by measurable wind.)

The official high at San Diego’s Lindbergh Field was 52 degrees, only a degree above the record low high temperature of 51 set in 1903. Other highs included 40 in Campo, 47 in Poway, 49 degrees on Point Loma, 51 at Fallbrook, 50 at San Diego State University and 57 at Oceanside. Coronado was the warmest spot at 60 degrees. Today’s predicted high in San Diego is 54 degrees, with near-record cold again tonight, followed by gradually warming days through Saturday, with a chance of light rain by late Friday as a new but milder front approaches.

Shigehara explained that the weather front brought little precipitation because the accompanying air mass below the moisture was extremely dry.

“We actually had rain with a humidity of 60%,” Shigehara said. The coastal snow flurries resulted from the cold air mass keeping precipitation from turning into rain as it fell to the ground.

“It’s very unusual, since normally we don’t get the cold coming from Siberia,” Shigehara said. “Normally, we get the Yukon Express from the Arctic Circle or Alaska.”

Also, Shigehara said that such cold snaps usually bear down on Southern California in January.

Growers were bracing overnight for the inevitable damage that comes with these air masses, particularly when temperatures in the low 20s last for several hours.

Assistant County Agricultural Commissioner William Snodgrass said any major damage to strawberries would be costly for growers, since their crop now commands a premium price--$2 a small basket. The berries are the only ones now being harvested in the state.

Snodgrass said severe frost, in which temperatures in the low 20s last several hours, could damage not only ripened fruit but berries still developing in the ground. With such damage, plants would require up to 1 1/2 months to recover, by which time growers in Ventura and Monterey will be harvesting, bringing prices down to $1 for two or three baskets.

“If there is damage to the crops now, but the fruit can bounce back next week, then we’re OK,” Snodgrass said.

Snodgrass said that both berry and avocado growers would irrigate their plants overnight, because water--at a temperature of about 50 degrees--helps insulate crops--even as the water freezes--much in the way an igloo insulates.

“As long as the cold does not penetrate inside the fruit, the fruit is OK, although ice on citrus would result in some scarring” of the skin, he said.

But the lack of wind and clearing skies could hurt some growers’ efforts, Snodgrass warned, because wind creates friction as it moves over fields and groves and produces heat, and clouds radiate heat back to the ground. Without the wind and cloud cover, cold air will develop in a grove or basin, and becomes even colder as it settles undisturbed, he said.

Although avocados are harvested at various times throughout the year, the predicted cold would have consequences as well for the $100-million a year crop. More avocados are grown in San Diego County than anywhere in the country.

“There’s not that heavy a harvesting going on right now, but immature fruit could be hurt if the temperature went down, for example, to 23 degrees for four hours,” Snodgrass said.

Fruit production could be affected for a season or more, depending on severity of the freeze to an avocado tree, he said.

COLD HITS L.A., rest of Southern California too. B11