Hey I'm glad meteorologists can teach people new things! So not quite, a tropopause fold/depression occurs just behind a upper-level jet stream associated with a strong cyclone, in this case a piece of the tropospheric Polar Vortex that's been pinched off.

The reason why Bernoulli acceleration occurs at the fold is a difference in density: the bottom of the stratosphere directly above the tropopause gets increasingly warmer, drier, and therefore more stable than the airmass below it. So, that rapidly increasing stability creates the "flow squeeze" effect between the fold and the White Mountains, thus accelerating the winds.