Arrow-right Camera

Washington Voices

Microclimates cause wide differences throughout region

Thu., Dec. 20, 2012

With 2012 coming to a close, many reporting weather stations will vary in terms of total precipitation for the season. For example, at the Spokane International Airport, about 21 inches of rain and melted snow has been measured since Jan. 1. In Coeur d’Alene, a station is reporting near 42 inches of moisture. This is a huge difference within a region of about 35 miles.

Within short distances, there are many lakes, mountains and valleys that host a variety of climates. Many observers have reported temperature and precipitation figures that greatly vary from the official reporting stations used by the National Weather Service.

These “microclimatic” differences between one area and the next are caused by topographical features including latitude, longitude and, of course, altitude, which often dictates amounts of snowfall and precipitation. The proximity to water, especially large bodies like Lake Coeur d’Alene, Badger Lake, Hayden Lake, Lake Pend Oreille, Liberty Lake and others, also results in wide climatic differences in neighboring regions of Eastern Washington and North Idaho. For example, during the summer months, residents near the lakes often experience milder nights and cooler days because of the moderating effects from the huge bodies of water. Readings may differ as much as 3 to 5 degrees from inland locations.

During the winter season, towns away from these lakes have been as much as 10 to 20 degrees colder during the nighttime hours. Some area towns sit in tiny valleys where cold air will often settle, resulting in much more frigid conditions than in slightly higher areas.

Within a wide range of at least 40 to 50 individual microclimates in this area alone, snowfall amounts vary significantly. Towns near or in mountain locations usually receive double the amount of snow in the winter months compared to towns at lower elevations. Even below 2,500 feet, there have been many instances when towns near a particular lake would receive only traces, while just a few miles away, as much as 3 to 6 inches of snow will have been measured. Theses variations often occur near Coeur d’Alene.

The Cascade Mountains to the west of Spokane act as a shield from air masses that originate from the Pacific Ocean. Therefore, Spokane receives much less precipitation than Coeur d’Alene. Storm systems that move in directly from the west have to climb over the Cascade Mountains, resulting in heavier amounts of precipitation as the air condenses. But, as the storms descend from those mountains on the other side toward Eastern Washington, the air warms up and dries out. This phenomenon is commonly known as the rain shadow effect. However, as one moves closer to the Idaho mountains, the air is once again forced upward. As a result, rain and snow becomes more abundant in these regions.

As things now stand, January and February should be a bit colder and snowier than normal in our part of the country. Sea-surface temperatures have cooled along the equatorial regions, which should increase the flow of moisture from the Gulf of Alaska.

If you have any questions or comments, you can contact Randy Mann at www.facebook.com/wxmann, or go to www.longrangeweather.com for additional information.


Click here to comment on this story »