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Conditions ripen for October snow

| October 4, 2021 1:08 AM

The fall season for North Idaho and the rest of the Inland Northwest is setting up to be wetter and perhaps cooler than normal.

We’ve already seen the beneficial rainfall that pushed our September total at Cliff’s station to 1.66 inches, compared to the normal of 1.48 inches.

The huge ridge of high pressure that’s been locked over the western states for months on end will finally be weakening enough to allow more storms into our area later this month.

Some of the long-range computer models are pointing to below-normal temperatures as we may start receiving a flow from a northwesterly direction out of the Gulf of Alaska. During the winter season, this developing pattern is what would bring us the snow.

Cliff and I wouldn’t rule out the possibility of some measurable snowfall later this month, perhaps as early as next week. We have some cold storms coming, so it’s going to be close on whether we'll see snow in the lower elevations.

As I’ve been saying for weeks, we’ve been in a pattern of “early.” In recent years, our seasons have been developing earlier than normal. In September 2019, we had a record 1.1 inches of snow, followed by 5.5 inches in October. The first snowfall in October 2019 occurred on the 9th with a record 1.8 inches.

Last year, October 2020, an incredible 7.7 inches fell on Oct. 23 with another 0.2 inches reported on the 24th. An all-time record of 7.9 inches of snow was reported just over 12 months ago.

If the upper-level winds favor a northwest flow over our region in the next several weeks, then we may see the third October in a row with measurable snow in the Coeur d’Alene area. If this pattern doesn’t fully develop this month, it still looks very favorable for some snow in the mountains.

One of the reasons we may have better odds for above-normal snowfall for the 2021-22 season is the redevelopment of the cooler-than-normal sea-surface temperature event, La Nina, in the waters of the south-central Pacific Ocean. For much of the year, we’ve been in a La Nada, the in-between warmer El Nino and the cooler La Nina.

Despite the fact that we continue to be in a La Nada pattern, sea surface temperatures continue to cool along the equatorial regions. If the trend continues, it’s very possible that we may see the formation of a new La Nina over the next several months. In fact, the cooling has intensified over the last several weeks, a further indication that a new La Nina may be around the corner.

However, there’s always something that could change the direction of ocean cooling. Very close to the West Coast of South America, there's a small region of ocean waters that has warmed to above normal levels. This is likely to be temporary, but the area needs to be watched very carefully.

If the warming in this region were to continue and suddenly expand, then the focus would turn to a new El Nino rather than a La Nina. Right now, there is not much evidence of the expansion of the warmer waters near the South American coastline.

Although this pattern is good news for the Northwest, it’s still very dry in California. Seasonal moisture totals for the Golden State are about 30 to 50 percent of normal for the second year in a row. Hopefully, some of the moisture expected in the Northwest will work its way southward into California by November.

Much of Northern California has seen very light amounts of moisture since the middle of March, and this has been one of the driest periods since the mid-1970s. With the lack of moisture and extreme to exceptional drought conditions in many areas in the West, this is another one of the worst fire seasons in history.

By extreme contrast, the eastern third of the country and the southern states have seen much above normal rainfall. It’s one of those scenarios where it’s practically bone-dry in the West and very wet in the East.

Thanks to the current sea-surface temperature pattern, this has also been another active tropical storm and hurricane season. As of the weekend, there had been 20 named storms compared to the normal of about 13.

There have been seven hurricanes through September. Hurricane Ida was a monster Category 4 hurricane that made landfall in Louisiana. Major flooding was seen from Ida as well as the impacts from Tropical Storm Fred and Hurricane Henri.

Seven named storms have made landfall in the U.S. this year. Total damage from these tropical systems thus far has been over $55 billion, the fifth-fhighest in history and the season is not over until the end of November.

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Contact Randy Mann at randy@longrangeweather.com

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