We are getting into the thick of the rainy season


PORTLAND, Ore. (KOIN) – November is the second wettest month on average for Portland. If you didn’t know that yet, you should be ready for rain. I just wanted to get that out of the way before I go on to discuss the wet forecast and what may see this month.

Before we get to that, let’s quickly go over the rain totals for the month of October. We had finished the month with 3.72 inches of rain. That made the second month in a row that we had a surplus of rain in Portland. It put us over the average by 0.30 inches. It’s not much, but we will take it.

As far as making large strides with the drought conditions, the month didn’t improve a lot of locations, but it also didn’t exacerbate the drought. The northwest Oregon coast and some locations up in Washington did have improvements. That means, we can still use plenty of rain ( just at a reasonable pace). I want to point out the stretch from Oct. 19 to Oct. 29, where we had measurable rain each day. It was that 10 day period that brought in the soaking rain (2.82 inches) for the month. Up to that point, we were actually below average for the month.

We know it doesn’t take that long to increase the rain totals around here after a round or two of tropical moisture. That tropical moisture comes from the atmospheric rivers that meander to the Pacific Northwest (PNW).

We have had a balance of below, near average, and above-average November years going back to 2015. The back-to-back dry November years in 2018 and 2019 were unusual. The 30-year average for the month of November is 5.45 inches of rain. We were much closer to that in 2015 and 2020. There are years that we do not stop at the 5.45 mark and we keep going. Both 2016 and 2017 were surplus years, bringing in over 6 inches of rain, in November, for Portland.

What is expected this November? Weather models are trending towards a wetter than normal November for the PNW. We are definitely starting the month with an active weather pattern, which is going to bring in multiple systems of rain. We will likely pick up rain each day this week and potentially into the weekend. There doesn’t appear to be anything in the long range that suggests a weather hush will descend over the active Gulf of Alaska waters. The jet stream continues to guide in system after system for potentially the first 10 days. Very similar to that aforementioned span of time in October that boosted our October rain totals.

This doesn’t mean we will have active atmospheric rivers that are associated with our November. They may be your run-of-the-mill mid-latitude cyclones that generate moments of rain and scattered showers. Sometimes it is strength in numbers (a chain of systems) and other events are lucrative plumes of moisture that skew our totals quickly (strong atmospheric river). It may be a combination of the two, which is more likely. The forecast should help out portions of the state that are east of the Cascades as well. This doesn’t always mean it will translate to hefty snow totals for the base of the ski resorts. It should mean snow for at least the higher segments of the mountains. It all depends on where the snow level drops, which is dependent on the situation.

If you swipe through the slideshow above, you will also see the temperature outlook for the month. The Climate Prediction Center (CPC) is projecting an equal chance for below, average, or above temperatures. November doesn’t tend to have the same drastic slide as October. It can be a temperature shock for October, where November, is more reasonable. We start the month around 58 degrees, wrapping up near 50. You need more of a rain jacket than a winter jacket.

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