Soggy December weather moving in, but, it’s not cold


PORTLAND, Ore. (KOIN) – If you thought last week was rainy, this week we turn it up a notch. There will be a dry window here or there but expect multiple opportunities for rain this week.

This afternoon and evening will be one of those dry slots in the forecast. The rain was mostly for the morning hours, with less of a threat for the rest of your day. It is always recommended that you check out the video forecast too so you can get a visual idea of the forecast as well. The afternoon should come with some sun breaks and temperatures pushing 50 degrees. That shouldn’t change much after reading this.

Let me take you to a wide scope of what is going on the next 24 hours. High pressure makes a quick stop on Monday afternoon. That is what promotes dry and stable conditions (for the most part). That means we won’t see much rain for the next 12 hours, depending on when you read this, we will call it dry until Tuesday morning. We have a classic December mid-latitude cyclone, disturbance, moving through the Gulf of Alaska. You can see that area of low pressure and rain associated with that on the graphic below. A cold front will transition through the region during the morning hours Tuesday. You can see the path of the jet stream from the second image in the slide show.

Precipitable water is limited on Monday, resulting in just a few isolated showers. You’ll notice the flow of the wind is coming in from the northwest with our setup today. That changes on Tuesday, as a southwest flow turns, carrying in slightly warmer air and transporting more moisture our direction. This is about the time that our front decides to move inland and the rain becomes more dependable. When should you grab the rain gear? Before you head out the door on Tuesday would be a good idea. Rain totals likely pushing .25 inches around the valley.

I want to take you to a graphic that is going to be changing through the week, but it will give you an idea of the trend. The forecast rain total can be a talker during this time of the year. Weather models are pushing over 2 inches of rain from Monday to Sunday. It is actually leaning towards 3 inches with lower amounts east of the Cascades and to the south in the valley. I would plan on this total being lower, as models tend to overplay the outcome this far out. However, I think it is possible we push 1.75 – 2.00 inches by the time Sunday finishes off. That will get us a little closer to our average, if not put us over. What is important about this graphic, is that it is supporting a wet forecast the next five to seven days.

What can bring in the higher rain totals? That typically is warmer air, it can carry more moisture. That means the valley is likely to refrain from the cold winter temperatures at this time as we continue to bring in moisture of the southwest.

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