California wine grape growers and vintners are tallying up the damage caused earlier this month when a bitter-cold Alaskan weather front slowly moved through a large chunk of the state’s Central Coast premium wine grape growing area.

Damage is unquestionably extensive in the northern San Luis Obispo and Southern Monterey counties around Paso Robles, Calif., and north to the King City area where tender 2011 crop buds were fried from hours of mid-20 degree temperatures.

Some vineyards may not have a crop to harvest this fall due to the April 8-10 frost.

Vintners and growers from Solano to Santa Barbara counties are assessing the damage. Although the vines may push secondary buds to set a crop, Stacie Jacob, executive director of the Paso Robles Wine Alliance, reports growers are estimating the loss could range from 30 percent to 50 percent of the 2011 crop from the area’s 26,000 acres of vineyards.

“Although the magnitude of the frost was widespread and prolonged, it is too soon to tell exactly what the loss will be. It all depends on what the secondary and tertiary buds do from now on,” she noted.

Viticulture consultant Lowell Zelinski of Templeton, Calif., estimates that more than half of vineyard acreage in the Paso Robles area was damaged by frosts.

“15,000 of the 26,000 acres in the area suffered some damage,” said Zelinski. “Right now I would estimate 25 percent of the total acreage suffered a 90 percent crop loss. Losses will be so heavy that it will not pay to harvest some vineyards.”

“I have seen vineyards that look like they have been sprayed with paraquat. Buds are black. It is going to be bad.” Zelinski estimated only about half the vineyards in the Paso Robles area were covered by crop insurance when the frost hit.

Richard Smith of Valley Farm Management in Soledad, Calif., in Monterey County said it was a “hyper cooling” event. Low spots prone to frost were spared while upslope vineyards were hit.

“The morning of Friday, April 8, we hung ice from nine to nine. We had all 400 acres of frost protection (overhead sprinklers) running in Hames Valley,” Smith said. This is near the small southern Monterey community of Bradley, Calif., just north of Paso Robles.

“The coldest five acres were beyond our ability to protect. My neighbors were less fortunate,” Smith said.

In a northern Monterey County wine grape growing area called Arroyo Seco, a “real unexpected cold cell-hyper cooling-thunderstorm-cloud-clearing event” hit at an elevation 100 feet higher than the valley floor.

“We have 100 acres of virtually 100 percent shoot burn, and my neighbors on the adjacent west side of the road have another 100-150 acres of damage,” Smith said.

A number of places had cold air dropping down draws and canyons and delivering a cold shot to areas where there are not normally frost issues.

Smith said he was fortunate to suffer what looks to be a 50 percent crop loss on 100 acres out of the 3,000 he farms. The most significant damage was in an area from King City, Calif., south to Paso Robles.