Will La Nina bring us a lot of snow this season?

The weather pattern in early December over the western states has “not been typical” of a La Nina event. As mentioned in previous columns, La Nina is the abnormal cooling of sea-surface temperatures along the Equatorial regions.

Cliff tells me that the first part of December, prior to the snowfall on Friday, was the driest in recorded history in Coeur d’Alene. During the first two weeks of the month, we had only .20 inches of moisture. The previous record for the least amount of moisture was .22 inches set back in 1929. The normal, by the way, is about 1.8 inches of rain and melted snow.

On Friday, a storm intensified and brought about 6 inches to Cliff’s station. The total for the season, as of late Sunday, is over 18 inches, close to normal.

At Spokane International Airport, a record 7.1 inches of snow fell. This led to numerous traffic accidents due to the slick conditions. Be careful out there. There should be more snow coming in early 2018.

One of the reasons we have this crazy weather pattern is that polar vortex. This is a relatively large upper-level low pressure system consisting of large masses of cold, dense Arctic air that is located near the North Pole. For much of this late fall season, it’s been located near southeastern Canada and the Northeast. In January of 2017, it was near our region and brought us the unbelievably frigid temperatures. From Jan. 1 – 17, Coeur d’Alene’s high temperature was below the freezing mark.

The big question is whether we’re going to see a white Christmas in North Idaho. For the mountain areas, it shouldn’t be a problem. In Coeur d’Alene and other areas in the lower elevations, Cliff and I believe there’s a pretty good chance.

There is another storm system on Tuesday that looks warmer and will likely bring mostly rain to the lower elevations and wipe out a lot of snow on the ground. But, what moisture is left from that storm system will change to snow by Tuesday night with snow showers on Wednesday. Another system at the end of the week should also bring us more snow showers, increasing the chance for a white Christmas.

The other part of the country that will likely have a white Christmas will be near the Great Lakes and the Northeast. Cliff and I have had a number of conversations and we both agree that these are unusual weather patterns and not typical of the cooler La Nina patterns we’ve seen in the past, but that may change.

We also see an increasing chance of measurable snowfall shortly after the new year. With La Nina events, we often see snowier than normal winter seasons, so there’s still a good chance of a healthy snowfall season over the next few months. However, if the big ridge of high pressure that’s located over the western states rebuilds, thanks, at least in part, to the polar vortex in the east, then we could get an entirely different scenario. Remember, we’re in this wild cycle of “extremes,” which has gone from wet to dry and so forth in short periods of time.

The latest sea-surface temperature data still shows additional cooling of ocean waters along the Equatorial regions. Most computer models and forecasts continue this weak La Nina through at least the early portion of 2018, but most forecasters believe that this cooler sea-surface temperature event will dissipate by the spring season.

If the La Nina phenomenon doesn’t expand early next year, and sea-surface temperatures begin to rise much sooner than expected, then the winter forecast will have to be revised. As mentioned in previous columns, sea-surface temperatures have been going “up and down” in short periods of time over the last year.

While ocean temperatures have been cooling near the Equator, we’re also seeing a lot of ocean warming in the western portions of Gulf of Alaska and off the coastlines of Central and Southern California. This pattern could lead to a drier winter in the Southwest as well as Southern California where rain is desperately needed.

But, if La Nina weakens in the coming months, Southern California could go from “fires to mudslides” as the warmer waters off the state’s coastline could increase the chances of storms moving into that region.

Over the last several weeks, residents are describing parts of Southern California as “a war zone.” One big wildfire, the Thomas Fire in Santa Barbara County, has burned over 260,000 acres and is considered the third largest in the state’s history.

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Contact Randy Mann at randy@longrangeweather.com