PORTLAND, Ore. (KOIN) – Any time now.
That may be the feeling boiling up as Portland is waiting for our first soaking rain of the upcoming fall season. It’s about this time of the year when we notice a change in our precipitation. Instead of the spotty summer showers, the more water-invested, mid-latitude cyclones typically start to show up. These systems can bring in a potent cold front, a rush of low-level moisture and an extended period of time where rain is coming down. Most years, it’s around the second or third week of September when we have our first rain event that carries a quarter-of-an inch or more. Some years, our first wetting rain, may even be over an inch.
We have had more significant rain events happen right around this date in the past. The last two years brought in our first soaking on Sept. 18. That means our atmospheric river season is getting closer and closer. Soon we will be discussing those plumes of moisture that are our major source of water for the year.
On Tuesday, southern Oregon brought in very useful rain from the system that is spiraling off the coast of northern California. Before the sun even made an appearance, Medford had collected nearly a half-inch of rain. This is the type of wetting rain that helps fire suppression. You can see that Klamath Falls brought in over a half-inch of rain, with measurements as far north as Bend. This is the type of moisture we are waiting on up here in the Willamette Valley.
Those chances don’t seem to be moving in for Portland or nearby neighborhoods in the coming days. As new weather data comes in each day, it sure seems like the weather pattern may actually be more dry than wet. We could potentially wrap up the rest of the month with little to no measurable rain. Portland is currently 0.75 inches behind what’s normal for the month of September. This may be one of the driest September years on record.
If we finish the month where we are at, it would be one of the top 10 driest September months going back to 1940. Usually, it takes one of those atmospheric rivers to bring us back up to snuff. We have 10 more days to collect as much water as we can up here. This is great weather for outdoor climbing and exploring hikes. We have had a good run of mainly dry weekends to get out for all the fun late summer events. Use these days wisely, because the rainy season has no sympathy for your outdoor plans.
Something to think about as we wrap up the month. We typically have one day that brings in a half-inch of rain or more in the month of September. Will we sneak that in before the month finishes? Right now, we have only fulfilled two of those days in the graphic below.