EDITOR’S NOTE: We are very excited to announced that the Pioneer will be publishing Tillamook County’s weather prognosticator Gordon McCraw’s weather forecasts as a public service. Thanks so much, Gordon for sharing your weather wisdom with Pioneer readers.
By Gordon McCraw
Tillamook Area Forecast: Monday, December 16, 2019, 10:35am
Well, it looks like we will catch up on our annual rainfall average by the end of the week. The weak ridge of high pressure over the area will shift eastward tonight into tomorrow morning, and then the rains came!
Tomorrow (Tuesday December 17) afternoon a disturbance moves across bringing in some light rain Tuesday night into early Wednesday morning when we will see more moderate rain moving in ahead of a stronger front, then things start getting interesting and more complicated. We expect a trough of low pressure to race across the Pacific towards the Pacific Northwest. As it moves east and southeast, the tail end will absorb some tropical moisture that will race up the trough and become involved with a warm front that will bring rain into the area Wednesday night or early Thursday morning. There may even be a low pressure area develop and move northeast towards Washington that could bring some high winds into the area Thursday.
The result of all this is there will likely be a moderate to strong Atmospheric River event set up. Some of the current uncertainty is exactly how this event will respond. The overall pictures painted by the models are, either the atmospheric river stalls and a narrow area gets an awful lot of rain, or it moves back and forth, up and down the coast from Thursday night through early Saturday, and shares the moderate to heavy rain with a lot of folks. At this time, there is a lot of uncertainty on exactly where the area of heaviest rainfall will land.
I have observed that Tillamook County River forecasts continue to increase the crest levels and now several rivers appear to approach Action Stage by Saturday morning. I would expect these forecasts, and all the other river forecasts up and down the coast, and even over in the valley, to change as the models begin to paint a clearer picture on this event. If I can offer good news for this, our rivers are relatively low, especially for this time of year, so this helps. The only other bad news, we are coming into a period of higher tides again that peak over Christmas.
So, what we know is, there will be a system bringing moderate to heavy rain to northwestern Oregon and southwest Washington Thursday through early Saturday, there is moderate confidence that the result could be 2-4” of rain over in parts of the valley, and 3-8” (or more) of rain into the Coast Range. What we don’t know right now is exactly which river drainage areas will get the heavier rains, thus, exactly which rivers will flood is uncertain for now. We are not real sure about the winds Wednesday night or Thursday either.
I would suggest that if you live in, or your business is in a flood prone area, now is a good time to review your plans, or to make your plans. You might consider filling your gas tanks, charging your batteries, and restocking some of your supplies. A briefing and reminder to the newer folks. These heavy rain events can not only cause river, small stream and urban flooding, it can also cause land and rockslides, and culvert issues that block roads. The high winds could down trees that block roads and cause power outages. Continue to monitor the weather as things will be changing up till the event. As I like to say, get ready to get ready!
Gordon McCraw – Gordon’s Tillamook Weather Center – http://www.gamweather.com/forecast.html