Goto https://weather.gc.ca/map_e.html?layers=radar&zoom=7&center=49.22362589%2C-90.26372876
Place your cursor above the map and slowly start panning down without lifting your fingers.

In Firefox as soon as your cursor is over the map you start zooming the map. In Chrome and Safari you keep scrolling until you lift you fingers from the touchpad.

This also seems to happen if the fingers aren’t touching the trackpad. On MacBook, if I perform a quick two-finger swipe (kind-of like a flick gesture) to scroll the page, the scrolling will still stop at the map, even though my fingers are no longer touching the trackpad.

(In reply to Šime Vidas from comment #1)

This also seems to happen if the fingers aren’t touching the trackpad. On MacBook, if I perform a quick two-finger swipe (kind-of like a flick gesture) to scroll the page, the scrolling will still stop at the map, even though my fingers are no longer touching the trackpad.

Indeed, momentum scrolling has a similar issue; that one is tracked in bug 1746304.