Tendrils of moisture to grab hold of the Pacific Northwest


PORTLAND, Ore. (KOIN) – I don’t want to distract you from the sunshine and the dry weather, but we have a series of rainy days on the way. Clear signs of stormy weather are out west, eventually showing up here in the Pacific Northwest. No worries for your Monday afternoon and evening. You can head out and enjoy the weather now. Take that fall bike ride or hop on a boat down the river while you still can. With temperatures pushing to the mid 60s on Tuesday, you shouldn’t have too many problems for the next 24 hours. Now, do I dare say it is construction season for weather? This is when conditions start to become more active and the ability for a storm system to move in and impact everyone is heightened. It sure looks like the span of Wednesday through Sunday may bring in rain for all. How much and where the heavy rain is targeted is still being worked out. The tea leaves are thinking more moisture south to California, but we are expected our fair share here too.

In the meantime, look at this mammoth system spiraling in the Gulf of Alaska today.

What exactly are these tendrils of moisture that are moving in? These are the plumes of moisture that we usually call atmospheric rivers. Below is a slideshow, which clearly shows the setup of multiple plumes of moisture that are set to impact the PNW and California this week/weekend. The most substantial atmospheric river that is nested in a backing of moisture, is set to arrive over the weekend. It is more than possible that it finds a place farther north, bringing in more rain to Oregon and that would also translate to mountain snow. The weakest atmospheric river this week is expected on Wednesday. You will notice that the moisture will arrive in more of a showery environment, not a steady consistent rain. It’s those days where it is cloudy and raining all day where the atmospheric river is evident. Most of our more impactful atmospheric rivers come in the winter. You may recall December 2015 where we had over 15 inches of rain for the month. That was a busy month with hefty atmospheric rivers coming in.

What is also important to note, is the jet stream will help back the transport of moisture. An atmospheric river may bring in more moisture, but it is also important to recognize the strength of the wind. An important piece to the strength of an atmospheric river is the ability to transport that moisture. The jet stream isn’t necessarily organized early in the week. This will become more zonal near the weekend, coming in strongly from the west to the east. It is meandering and bending right now, with the strength of the jet west of that massive system we were admiring in the satellite above. Right now, we have a transient ridge of high pressure moving through the region, allowing for sunshine and broken clouds. Keep up the good work, ridge.

With all that information in mind, you can bet that the rain chance this week is going to be up near the top of the box. There will be some dry try late Wednesday into Thursday morning, before the next tendril of moisture comes our direction.

Here is the question of the week: What do you like to do during the fall, rainy season? Are you into cooking warm meals? Do you toss on the rain gear and go for a low elevation hike? Do you dream of snow on the mountain and prep for winter skiing and snowboarding? Do you get a wanderlust bug and travel? With an extended period of gloomy days coming our direction, you may be turning your routine over for the depths of the fall season. Now may be the time to get a new book and stock up on wood.

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