Storms and other winter weather expected well into January should keep snowpack in most of Idaho close to or slightly above normal.

An active weather pattern is forecast for the next 10 days, state Department of Water Resources hydrologist David Hoekema said Dec. 31.

Northwest River Forecast Center five- and 10-day forecasts “indicate that precipitation should be close to normal, except in the central mountains.”

“We have just over 40% of our peak median snowpack, so we need an active weather pattern to continue through the winter,” he said.

Starting in January in a typical year, snowpack increases by about 20 percentage points a month until reaching 100% April 1, Hoekema said.

“In some areas of the state, we are a month ahead, and in some areas we are a couple of weeks behind,” he said.

Few years follow the average pattern in linear fashion, Hoekema said.

And some river basins melt out later because they are higher in elevation while lower basins such as Owyhee and Weiser tend to melt earlier.

Most of Idaho’s weather comes from the west or south.

Hoekema and others will watch for ridging over the Pacific Ocean, which can keep rain and snow from coming in as storms typically move around the high-pressure ridge.

A mild La Nina weather pattern is expected to bring additional moisture to the state’s northern region and the Pacific Northwest, he said. La Nina’s impact typically varies in southern Idaho.

Relatively few Idaho basins have less than normal snowpack for this time of year, Hoekema said in a report that draws from USDA Natural Resources Conservation Service Idaho Snow Survey data.

They are Little Wood at 84% of normal, Big Lost at 85%, Little Lost at 86%, Birch Creek at 84%, Lemhi within the Salmon basin at 87%, Henry’s Fork at 91% and Upper Snake River at 92%.

The water year started slow and warm, as October was the ninth warmest and 18th driest month in 130 years of Idaho record keeping, Hoekema said.

Temperatures were just below normal and precipitation slightly above normal in November, he said.

December brought mostly above-normal precipitation except in the east-central mountains and some points to the north.