We’re approaching the middle of October and getting closer to the full moon lunar cycle beginning on the 16th and continuing through the 21st. This is often the period that gives us a pretty good indication of what the upcoming winter season may be like.

Cliff and I believe that the rest of this month should have precipitation totals above normal of 2.22 inches. September ended up very close to the average of 1.48 inches as 1.44 inches of rain was measured.

Many of our long-range forecasts are based upon the lunar cycles. Farmers have been planting by the moon for thousands of years. Everyone agrees that the full moon, and even the new moon, lead to noticeable changes in ocean tides. We believe that if the lunar cycles can affect the tides of the oceans, then why not the tides of the air?

Potent storm systems usually need the support of upper-level winds as they move across the continents to produce significant precipitation. Long-time observations and data analysis does show a correlation with the lunar cycles and behavior of the upper-level jet stream patterns.

During the full moon and new moon cycles, upper-level winds will change as the low pressure troughs, or dips in the jet stream, become greater while the high pressure ridges will amplify, especially toward the end of the cycle. By contrast, during the first and last quarter lunar phases, the jet stream often becomes more zonal and storm systems are usually not as intense.

In addition to the increased moisture, our area will often see its coldest weather in the winter and its hottest temperatures in the summer during a full moon event as the troughs and ridges become more pronounced.

Cliff did an analysis of the volume of precipitation during all lunar cycles for our area in 2015. His data shows that North Idaho received a whopping 80 percent of its total moisture during the full and new moon lunar cycles. During the last and first quarter cycles, only 20 percent of the season’s moisture was received.

During the full moon phase, approximately 42 percent of measurable precipitation fell in our region last year. The new moon cycle had 38 percent. The normally dry and warm last quarter reported only 6 percent while the first quarter had 14 percent of the season’s precipitation for 2015. During the summer of 2016, only .01 inches of rain fell during the last quarter cycle.

These cycles don’t work every single time, but we have found that they are reliable about 75 to 80 percent of time, especially in the Northwest. Those are pretty good odds.

If these patterns work out, our winter of 2016-17 continues to look snowier than normal as sea-surface temperatures are cooler when compared to this time last year. We could also see one or two Arctic outbreaks during one of these full moon events during the winter season. This is certainly good news for the many skiers and snowboarders in our region.

In terms of our local weather, as of last Friday, moisture totals for Coeur d’Alene are over 20 inches for the season, which is close to normal. In Spokane, its seasonal moisture total is about 9.50 inches. That total is below the average of about 11 inches to date.

We should see a brief break from the wet weather before more rain arrives toward the end of this week. It’s looking wet the following week during the October full moon cycle. We’ve already seen snow fall in the mountains and I expect more of the white stuff in the higher elevations during this time.

Once we get past the full moon cycle, the last week of October should briefly turn dry before more moisture arrives around the new moon cycle beginning on Oct. 30. The odds certainly increase for rain on Halloween, but there’s a chance we’ll fall between storms around that time. There’s also the chance we could see some flakes of snow in the lower elevations around the first week of November.

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Contact Randy Mann at randy@longrangeweather.com