Rain showers slowed down or stalled the harvest of wine grapes in the Pacific Northwest on Wednesday, but the weather forecasts calls for optimism and drier conditions beginning today.
“Over the next couple of days, expect cold (10-20 degrees below normal) and generally wet conditions across the (Pacific Northwest) and down into California through Thursday,” reported Greg Jones, a Southern Oregon University professor and climatology renowned for his work with the international wine community.
“An upper level ridge will build in from the west from Thursday into Saturday bringing drier conditions and increasingly warmer temperatures (above normal for many locations),” Jones continued in his latest weather report to the wine industry. “A short wave trough will mix things up on Sunday with coastal and some inland rain from SW Oregon northward, but this should be short-lived as a ridge will build in over the west, pushing the storm track toward northern Washington and British Columbia. Models are not in full agreement, but most are pointing a drying period the first week of October.”
Through the middle of September, most vineyard regions in the Northwest were one to two weeks ahead of schedule in terms of ripeness.
In Idaho’s Snake River Valley, vineyard workers picked varieties such as Viognier in the morning hours before stopping as the rain increased. Longtime grower Ron Bitner pointed out that during the 1980s, it was not unheard of to pick Riesling for late-harvest wines in the Sunnyslope region near Caldwell, Idaho, during the later stages of September.
About a third of an inch of rain fell Tuesday in Idaho’s Snake River Valley.
Jones pointed out, “Well, fall clearly came early, or maybe we had such a great fall last year that we forgot what normal is? Conditions over the past two weeks were not seen in 2012 until the third week in October, but are not too unusual for the month of September on average.”
The data and forecast indicate that September still will finish warmer than of late.
“The 6-10 day and 8-14 day forecasts both point to a greater chance of warmer than normal temperatures in the PNW and normal throughout California,” Jones said. “Precipitation forecasts over the same time period point to a greater likelihood of generally drier than normal conditions, except along the coast from southern Oregon to the Olympic Peninsula.”
On Washington’s warm Wahluke Slope, temperatures the past three days have not hit highs above 68 degrees and have not topped 90 degrees since Sept. 15.
In the somewhat cooler Walla Walla Valley, conditions have been about the same, with temperatures the past three days not rising to 70 degrees. Temperatures have been somewhat warmer in the Yakima Valley, though the past two days have seen highs below 70 in Prosser.
Similar – even cooler – trends have been apparent in Lake Chelan, where temperatures have barely reached 65 degrees the past four days.
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