A short distance can make a big difference
Late last year, I received a few emails asking about the climate differences between Spokane and Coeur d’Alene. The distance between the two cities is approximately 33 miles. Across much of the country, there is not much precipitation and temperature variability over a distance of 30 miles. However, most of the climate differences around this part of the world are due to elevations of particular towns, their latitude and longitude and, of course, the proximity to large bodies of water.
The Cascade Mountains to the west, the Rocky Mountains to the east and the many lakes often determine how much moisture falls and our temperatures. For example, Spokane normally receives about 16.5 inches of rain and melted snow. That figure goes up when one goes to the east as Coeur d’Alene has an annual precipitation total of 26.77 inches. The same is true with snowfall as Spokane normally measures about 45 inches each season while Coeur d’Alene picks up close to 70 inches.
In 2018, Cliff measured 29.21 inches of rain and melted snow. At the Spokane International Airport, only 15.95 inches of moisture fell. That’s quite a difference between the two stations.
As storms move in from the Pacific Ocean, rain will often fall in the Seattle area. When the moisture moves up the Cascade mountains, there is more condensation and cooling, which results in heavier precipitation and even snow as the air is usually colder in the mountains.
Once the air moves over the western portions of the Cascades to the eastern side, it descends and warms up and becomes drier. This process is known as the “rain shadow effect.” It practically looks like a desert area along Interstate 90 as you get toward many of the towns in central and eastern Washington.
As the storms begin to move into Idaho, they start to come into contact with the western portions of the Rocky Mountains. The air starts to rise and we receive more precipitation in Coeur d’Alene and surrounding regions.
Our region is well-known for its many lakes, mountains and valleys and has a variety of different “microclimates” within a relatively small area. In 2005, Cliff identified at least 27 microclimates around North Idaho.
The official reporting station for the National Weather Service for Coeur d’Alene is the Pappy Boyington Field (airport) in Hayden. Because this is an “automated” weather station, snowfall measurements are not taken at this location. Therefore, Cliff’s measurements of snow for Coeur d’Alene are valuable as there is no official weather station in the city limits.
Based on the proximity to water like Lake Coeur d’Alene, Fernan Lake, Hayden Lake, Lake Pend Oreille and others, many of our observers have reported temperature and precipitation figures that have varied greatly from one place to another.
For example, during the summer months, residents near Lake Coeur d’Alene and other lakes often experience milder nights and cooler days due to the moderating effects from the huge bodies of water. Readings may differ as much as 3-5 degrees from inland locations.
However, during the winter season, towns away from Lake Coeur d’Alene have been as much as 10-20 degrees colder during the nighttime hours. There have been many occasions, even recently when the outlying areas will see measurable snow, but in the downtown area and near the lake, the moisture would fall as rain.
Snowfall totals will vary significantly from downtown Coeur d’Alene to places like Rathdrum, Dalton Gardens, Hayden and others. Cliff and I have seen towns near the mountain locations receive at least twice the amount of snow when compared to locations in the lower elevations. We’ve also seen cases in past years where downtown Coeur d’Alene and other nearby locations will report only traces of snowfall, but just a few miles away, places around the Silver Lake Mall and out toward Player Drive will pick up nearly 3-6 inches of snow with upwards of a foot of the white stuff in Athol, Twin Lakes and other towns closer to the mountains and farther away from the lake.
In terms of our local weather, Cliff and I still see a pattern of above-normal rain and snow through February as more storms move in from the Pacific Ocean. We still believe that Coeur d’Alene will receive about another 25 inches of snow for the 2018-19 season. Based on the current data, it’s quite possible that February will be our snowiest month.
As we get into March and April, conditions across the Inland Northwest should start to turn a bit drier. However, a lot does depend on the warming of the waters in the south-central Pacific Ocean. Many scientists and forecasts are still predicting a weak El Nino to be declared in February and have it persist through the spring season.
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Contact Randy Mann at randy@longrangeweather.com