The last week of September was glorious across the Inland Northwest.
Mean temperatures averaged 7 to 14 degrees above normal. Overall, last month was close to normal in terms of temperature and precipitation. The average reading was 59.8 degrees, which was 0.6 degrees above normal. Total precipitation for September was 0.69 inches. That was 0.07 inches below average.
Although fall officially began more than three weeks ago, winter is just around the corner. Many people have asked about La Niña, the cooler-than-normal sea-surface temperature in the south-central Pacific Ocean. Some have mentioned that other forecasters are predicting heavy snows for the Inland Northwest, a similar pattern during the winters of 2007-’08 and 2008-’09.
As mentioned in previous weeks, this current La Niña pattern is only moderate in terms of strength. It has also showed signs of weakening within the last two weeks but a slight intensification within the last seven days. However, it’s still uncertain on whether the current La Niña pattern will fall apart within the next few months or maintain its current intensity.
During the big winters of previous years, sunspot activity was extremely low. The quiet sun, combined with the cooler sea-surface temperatures, was likely a big influence in bringing our region the recent harsh winters.
According to the National Weather Service, a La Niña does not guarantee a snowy winter. For example, the winters of 1949-’50, 1955-’56, 1974-’75, 2007-’08 and 2008-’09 measured more than 80 inches of snow in Spokane. But, during the La Niña winters of 1967-’68 and 1970-’71, approximately 30 to 32 inches of snow fell in the area. Therefore, there are other cycles and oscillations that have an impact of upper-level wind flow patterns.
Last year, we had an El Niño, the warmer-than-normal sea-surface temperature. As a result, snowfall totals were well below normal across the Inland Northwest.
The upcoming winter should feature above-normal snowfall and below-normal temperatures thanks to La Niña and the low sunspot activity. Next week, I’ll have more detailed snowfall forecasts for the Inland Northwest.
In the meantime, we should see occasional showers mixed in with mostly sunny skies and warm days into next week. Around the third week of the month, however, things should be turning much cooler and wetter across the region.