White Christmas looks likely

Earlier this month, a new cooler-than-normal sea-surface temperature pattern, La Niña, was declared in the waters of the south-central Pacific Ocean. During La Niña years, weather patterns often favor above-normal snowfalls across the northern U.S., including North Idaho. In 2020, we had a weak La Niña, but our final snowfall total for the 2020-21 season ended up below normal.

As of late November, however, the upper-level wind patterns are starting to point to more snow across the Inland Northwest.

As of late last week, nearly 3.5 inches of snow had been measured in Coeur d’Alene, which is less than half of the normal to date. However, by this weekend or early next week, the chances for snow are expected to increase in Coeur d’Alene and the rest of the Inland Empire as we enter the normally wetter new moon lunar phase.

The new moon cycles are usually warmer, but there are indications that colder air will be mixing in to produce more snow than rain. By contrast, the full moon cycles are colder and the next one begins on Dec. 18. So, there is a better than 50/50 chance for snow during that time.

Based on these current weather patterns and the fact that we have an expanding cooler-than-normal sea-surface temperature event in the waters of the Pacific Ocean, Cliff and I see about a 75% chance of a white Christmas across the Inland Northwest — very good odds indeed.

Since 1895, there has been a white Christmas in Coeur d’Alene about 70% of the time, while Spokane International Airport sees a white Christmas around 50% of the time. However, within the last 20 years, there have been 15 years with at least an inch of snow on the ground.

The Christmas Day with the most snow on the ground was in 2008 with a whopping 44 inches. In 2015, there were 21 inches. That was during an El Niño year as ocean temperatures were warmer than average in the Equatorial regions. Big snowfalls in December during an El Niño year are not that common across the Inland Northwest, but they do happen about 25% of the time.

In 2016, there were 13 inches on the ground on Dec. 25. In 2018 and 2019, much of Coeur d’Alene barely had any snow on the ground on Dec. 25. It was disappointing that downtown Coeur d’Alene and other areas didn’t have any snow on the ground for Christmas during those years. In 2018, Cliff had slightly more than an inch on the ground on Christmas Day.

As frigid Arctic air pushes southward into the northern and central U.S., heavier snowfalls are expected from the violent collisions between the very cold air to the north and copious amounts of moisture from the North Pacific regions. This is a big reason why Cliff and I see a 75% chance of a white Christmas in the Coeur d’Alene region. In fact, outlying areas, Rathdrum, Hayden and Athol will have an 80% chance of snow on the ground on Dec. 25.

Elsewhere across the country, while much of the region from about I-90 northward has a 70 to 80% chance of snow on Christmas Day, there is a 70% chance of a white Christmas across New England.

Probabilities dip to 50% between Interstate 90 and Interstate 80, which includes most of Idaho, Colorado, South Dakota, much of Nebraska, Iowa, northern and central Illinois, northern Ohio and Pennsylvania and New York state, but not New York City. The Big Apple only has a 40% chance of a white Christmas this year.

Cities and towns in the central U.S. near Interstate 70 eastward to the Mid-Atlantic states likewise have around a 30 to 40% chance of seeing snow on the ground on Dec. 25. There is only a 10% chance of a white Christmas across parts of the southern U.S. this year, but anything is possible in this cycle of wide weather extremes.

Although we're in the cooler La Niña cycle, the southern U.S., including Southern California and the desert Southwest, are not likely to have any snow as we are in a warmer temperature pattern across the globe.

In other countries, much of northern Europe and northern Asia have a very good chance for a white Christmas. Many areas are already seeing snowfalls.

The northern British Isles have a 30% chance of a white Christmas, with a strong 80 to 90% probability of snow across Norway, Sweden and Finland in Scandinavia. From eastern Europe into Russia, there's a 60 to 90% chance for a white Christmas. Northern Italy only has about a 30% chance of seeing snow on Dec. 25.

• • •

Contact Randy Mann at randy@longrangeweather.com.