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I recommend a jacket that is "3 in 1". Basically when you buy them it comes with two jackets.
An outer waterproof shell with an inner jacket that you wear only when you need.
Something like the North Face Triclimate line or Columbia Interchange series.
These jackets are very light and pack nicely. Easy to change layers when needed.
They have dozens of options available. Just be sure you get one that actually states that it is water proof and not just "water resistant"