PORTLAND, Ore. (KOIN) — Spring showers will be our best friend Thursday and Friday and they’ll walk us right into the first day of spring on Saturday. High pressure, which generally keeps us dry and sunny, is shifting to the east overnight. Walking out the door in the morning: mostly cloudy, with showers approaching the valley. They may already be here by 5 a.m., but more likely there for the Oregon Coast to start the day. As our disturbance moves east, it will increase the rain chance in the valley, which is no doubt to start through the morning and it will continue into the evening.
Why don’t we try to iron out the forecast even further so you can have a better idea of the timing and the rain totals. You can follow along with the graphics in the slideshow and we will work through from the early morning into the late hours.
Light isolated showers start to show up in the Willamette Valley as of 5 a.m. The rain is there for the Oregon Coast and there may even be a few moderate showers at this time. The front bends back, which means the central coast and areas of the valley may have a few more showers before the northern areas. Notice how they spread into the central coast a bit more than up to areas like Astoria. Regardless, expect the rain up and down the coast by early morning hours. No issues from the Cascades to the east at this time of the day. At 10 a.m. the rain is starting to move into the valley and it will be fairly scattered. Showers may push into the Columbia River Gorge at this hour too. This isn’t going to be an all day rain affair, but it will come in waves with passing showers. There may be some isolated thunderstorms for the Oregon Coast at this time, especially to the south. Further enhancement tries to rev up the showers by the late afternoon into the evening. You can see that the Cascades may be fairly wet and the showers push east to even areas like The Dalles. It may be the late afternoon where we find our heaviest shower, especially east of I-5. The wave of moisture is then out of here by the late hours, after 9 or 10 p.m..
Let’s talk about the rain totals by late Thursday night. This isn’t an event where the rain is going to be massive for the coast and nonexistent for the rest of the state. In fact, we may have a few showers that produce some moderate rain in the valley as well. I do believe the weather model is overplaying the rain totals for areas like Portland, which has been consistent with the last couple of rain events. I’m in agreement with the rain totals over towards Newport, where they could potentially be even higher if there is a passing thunderstorm or two. I would aim more so to the .15-.25″ around the valley tomorrow. They’re likely overplaying the totals for Hood River and The Dalles as well. I would be more focused on the range of .10-.20″ in those regions. Either way, it’s one of the wettest days that we’ve seen this month, with very few soakers in the forecast.
Clouds may be broken at times tomorrow, especially in the morning hours of the day. You may get an opportunity for a peek of blue here or there. I would expect mostly cloudy conditions throughout the day in between those brief breaks.
As far as temperatures go? We do have some cooler air moving through. Expect the daytime highs tomorrow to just reach about the lower 50s, with unsettled weather through the week. Grab a rain jacket and keep it with you.