More rainfall than snowfall could precipitate an icy winter

The cooler and wetter fall season has arrived.

September was 4.7 degrees above normal levels at the Spokane International Airport. Only a half-inch of moisture fell, nearly three-tenths drier than average.

Weather patterns changed in a big way in October. As of early Tuesday, the average temperature for Spokane was about 4 degrees below normal. The airport has also received 2.25 inches of rain, about 1.4 inches above the October normal. The increased moisture has brought up the seasonal total to 12.19 inches as of a few days ago. We’re now about a quarter-inch above normal for 2009.

We still have a moderate El Niño, the warmer-than- normal sea-surface temperatures in the south-central Pacific Ocean. There are plenty of warmer ocean waters near the equatorial regions, but El Niño has showed signs of weakening over the past month as some cooler waters have developed along the immediate west coast of South America. If this trend continues, it’s possible that a new La Niña, cooler-than-normal sea-surface temperatures, may form in early- to mid-2010.

In addition to the warmer ocean temperatures, solar activity continues to be minimal. But, sunspot numbers have been increasing a bit over the last week; that may indicate the sun is finally becoming more active in terms of solar storms and energy output, which may lead to warmer weather in our region.

I still believe that our upcoming winter should see far less snow than the record-breaking winters of the last two years. It’s also likely that we will see more rain than snow, especially early in the winter, because of warmer temperatures, particularly at elevations below 2,500 feet. Even the ski resorts will probably see occasional rainfall up to 5,000 feet during the milder periods.

However, conditions should be cooler and wetter than normal through the end of November. It’s also possible that measurable snow will fall in the lower elevations tonight and in early November. It should turn milder and drier in the late fall and early winter. Snowfall is expected to increase during the second half of winter.

If El Niño maintains its strength, there’s a chance of freezing rain and a dangerous ice storm, especially in the valleys east of the Cascades.

Our normal seasonal snowfall at the Spokane International Airport is 45.6 inches. I still expect totals near 41 inches at the airport and about 47 inches on Spokane’s South Hill. The Spokane Valley should get close to 40 inches.

Mount Spokane may measure 165 inches of snow, with about 275 inches at Lookout Pass.