A series of showers may dampen Sonoma County this week, raising mild concern among grape growers about impacts on the crop during the height of harvest.
The light rain is expected to begin Monday, said meteorologist Austin Cross of the National Weather Service.
“Most of the rain will probably be south of the Bay Area, but there's still a decent chance of some light showers in the North Bay,” he said. “It slowly moves through the area, so there's still a possibility through Thursday.”
Just a few hundredths of an inch are expected to fall late Monday or early Tuesday, Cross said.
The Western Weather Group, a forecasting company used by many farmers, predicted trace amounts of rain, up to a tenth of an inch, throughout the week. It expected a 20 percent chance of rain on Monday and Tuesday, a 10 percent chance on Wednesday and Thursday and a 20 percent chance on Friday. Precipitation is likely Saturday and throughout the weekend, said their forecaster, Marc Walsh.
Although the total rainfall is expected to be low, moisture that lasts throughout the week could damage the crop, growers said.
“We're concerned,” said Duff Bevill, founder of Bevill Vineyard Management. “What you need is to have nice dry winds blow behind it. If you have a little bit and it stays overcast and crummy for a whole week .
Despite the mild threat of rain, growers have been lucky with mostly ideal weather this year, Bevill said.
“This is not a huge concern,” said Nick Frey, president of the Sonoma County Winegrape Commission. “You hope it misses us. If it does rain, we hope the wind blows and dries things out.”
State firefighters have warned that offshore winds are likely this week. While that is bad news for wildland fire conditions, it could be just what the grape growers need.
In general, grapes used to make white wine are most vulnerable to botrytis — bunch rot — after rains. Sauvignon blanc, one of the most vulnerable, has been harvested, and the grapes that still hang in the vineyards are mostly red varietals and chardonnay, Frey said.
Since July, the start of the weather year, there has been no rain in nearly all North Coast wine-growing areas.
Forecasters, however, expect the North Coast eventually to have a wet rainy season, Cross said. But at this time of year, weather patterns are hard to predict, and there's still a chance that the rains this week could miss the North Bay entirely.
“I wouldn't be getting in a bunker or anything for this one,” Cross said.