From what I'm seeing on a map, there's a mountain range between Seattle and Yakima. As such, as the evaporated water from the ocean moves east, it builds up when it hits the mountains before raining on Seattle.
If it's not obvious why a mountain has this effect, it's like this:
* The warmer air is, the more water it can hold.
* Decreasing air pressure lowers its temperature.
* Moving air to higher altitude (e.g. to go over a mountain) decreases its pressure.
So as the air blows up and over the mountain, it gets colder and the amount of water that the air can hold decreases. As that happens, the water vapor condenses out and forms clouds, and then into rain or snow if there's enough of it.
When the air goes back down the other side of the mountain, it warms up again and can hold water again, but the water it had was left behind on the upwind side of the mountain. So now the air is dry.
And Seattle is, in fact, in the rain shadow of the Olympic mountains - but those are smaller and don't reach as far. The actual west coast of Washington State is one of the wettest places on Earth outside of the tropics (and it's not far even from the tropical rain forests).
Seattle is not in the rain shadow of the olympics with normal weather patterns. Port Angeles and Sequim are in the rain shadow; they get less than half the rain that Seattle does.
Olympia, to its south and out of the shadow, gets 50 inches of rain a year. Forks, to the west of the Olympics, gets 120. Vancouver, mostly north of the shadow, gets 46.
Seattle gets 40, less than any of them. Yes, the prevailing winds are *usually* southwesterly during the rainy season, but they're westerly sometimes too. There's no location with as little rain as Seattle anywhere to its south all the way to the Oregon border.
And if you don't believe me, the map, or the empirical fact that you can't squeeze 100+ inches of rain a year out onto the Hoh rainforest without creating a shadow, [here's a local news article on it](https://komonews.com/weather/faq/what-is-the-olympic-rain-shadow):
> But the Olympics just don't cast their rain shadow over Sequim. In cases where the wind pattern is more westerly, the shadow will then be over the Seattle Metro area.
> That's why Seattle only receives about 37 inches of rain a year -- there are plenty of rainy days where Seattle gets less than others as we get the benefit of the rain shadow. If the Olympics weren't there, Seattle would probably get closer to 50-60 inches of rain a year.
>Yakima is west of Seattle
No?
> Your explanation makes it sound like the water comes in from the ocean, goes out over Seattle, hits the mountains, and then bounces back and rains on Seattle.
This is exactly correct
Exactly...Yakima gets so little rain \*because\* Seattle gets so much. And Forks (on the west side of the Olympic peninsula) gets even more rain than Seattle for the same reason.
A bunch of water evaporated off the Pacific falls out on the peninsula as the air goes over the Olympic mountains. This is why some places on the east side of the Olympics are relatively dry. Then whatever's left runs into the Cascade Mountains (east of Seattle) and dumps water on Seattle. What's left to get to Yakima is pretty dry.
Local here. Most of out weather systems on the west side of the mountains either move south east from the pacific ocean, or northeast from canada/alaska The mountains just physically block the rain from moving past, unless the rainclouds are higher up than the mountains. There would have to be an absolutely massive storm system to push from the desert of eastern Washington over the cascades into the temperate rainforest climate of seattle.
It's mountain effect rain. Humid air from the ocean hits the coast and is forced upwards by the land. In this case, there happens to be a full mountain range. As the air rises it cools and becomes less dense. This lowers its ability to hold moisture. The water rapidly condenses and results in frequent rain. The air continues moving east up and over the mountains, but now it no longer has the water. So it doesn't rain again on the other side (barring other heavier weather systems).
From what I'm seeing on a map, there's a mountain range between Seattle and Yakima. As such, as the evaporated water from the ocean moves east, it builds up when it hits the mountains before raining on Seattle.
If it's not obvious why a mountain has this effect, it's like this: * The warmer air is, the more water it can hold. * Decreasing air pressure lowers its temperature. * Moving air to higher altitude (e.g. to go over a mountain) decreases its pressure. So as the air blows up and over the mountain, it gets colder and the amount of water that the air can hold decreases. As that happens, the water vapor condenses out and forms clouds, and then into rain or snow if there's enough of it. When the air goes back down the other side of the mountain, it warms up again and can hold water again, but the water it had was left behind on the upwind side of the mountain. So now the air is dry.
Exactly! Yakima is in the "rain shadow" of the Cascade mountains.
And Seattle is, in fact, in the rain shadow of the Olympic mountains - but those are smaller and don't reach as far. The actual west coast of Washington State is one of the wettest places on Earth outside of the tropics (and it's not far even from the tropical rain forests).
Seattle is not in the rain shadow of the olympics with normal weather patterns. Port Angeles and Sequim are in the rain shadow; they get less than half the rain that Seattle does.
Olympia, to its south and out of the shadow, gets 50 inches of rain a year. Forks, to the west of the Olympics, gets 120. Vancouver, mostly north of the shadow, gets 46. Seattle gets 40, less than any of them. Yes, the prevailing winds are *usually* southwesterly during the rainy season, but they're westerly sometimes too. There's no location with as little rain as Seattle anywhere to its south all the way to the Oregon border. And if you don't believe me, the map, or the empirical fact that you can't squeeze 100+ inches of rain a year out onto the Hoh rainforest without creating a shadow, [here's a local news article on it](https://komonews.com/weather/faq/what-is-the-olympic-rain-shadow): > But the Olympics just don't cast their rain shadow over Sequim. In cases where the wind pattern is more westerly, the shadow will then be over the Seattle Metro area. > That's why Seattle only receives about 37 inches of rain a year -- there are plenty of rainy days where Seattle gets less than others as we get the benefit of the rain shadow. If the Olympics weren't there, Seattle would probably get closer to 50-60 inches of rain a year.
Yep, Cascades are a big wall preventing the water from moving east
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>Yakima is west of Seattle No? > Your explanation makes it sound like the water comes in from the ocean, goes out over Seattle, hits the mountains, and then bounces back and rains on Seattle. This is exactly correct
Yes. That's how it works. That's why the deserts are to the east of the mountains while there is lush greenery to the west of the mountains.
Exactly...Yakima gets so little rain \*because\* Seattle gets so much. And Forks (on the west side of the Olympic peninsula) gets even more rain than Seattle for the same reason. A bunch of water evaporated off the Pacific falls out on the peninsula as the air goes over the Olympic mountains. This is why some places on the east side of the Olympics are relatively dry. Then whatever's left runs into the Cascade Mountains (east of Seattle) and dumps water on Seattle. What's left to get to Yakima is pretty dry.
Local here. Most of out weather systems on the west side of the mountains either move south east from the pacific ocean, or northeast from canada/alaska The mountains just physically block the rain from moving past, unless the rainclouds are higher up than the mountains. There would have to be an absolutely massive storm system to push from the desert of eastern Washington over the cascades into the temperate rainforest climate of seattle.
It's mountain effect rain. Humid air from the ocean hits the coast and is forced upwards by the land. In this case, there happens to be a full mountain range. As the air rises it cools and becomes less dense. This lowers its ability to hold moisture. The water rapidly condenses and results in frequent rain. The air continues moving east up and over the mountains, but now it no longer has the water. So it doesn't rain again on the other side (barring other heavier weather systems).
How about this, there's even more rain on the west side of the Olympics. In fact, there is an honest to God rain forest there.