There's a question in the FAA commercial question bank that indicates that squall lines are nonfrontal, and the reference for the question points to the Aviation Weather Advisory Circular.

The word, "nonfrontal" (or any variation of it ie "non-frontal") does not appear in that document. Also, the word "squall" appears four times, and none of those seem to have information that indicates that they are nonfrontal.

Where is the FAA providing this information? Is it actually correct?

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    $\begingroup$ Errors on FAA questions would be par for the course. $\endgroup$ Jul 7 '20 at 17:58

If you go back and look at the previous version of that AC, AC-006A, the index has this definition:

squall line - Any nonfrontal line or narrow band of active thunderstorms (with or without squalls).

I guess that the question in the question bank was based on AC-006A, which was current until 2016. As for today, chapter 12 of the PHAK has a slightly different definition (p.12-23). It says that squall lines are not necessarily frontal:

Squall Line
A squall line is a narrow band of active thunderstorms. Often it develops on or ahead of a cold front in moist, unstable air, but it may develop in unstable air far removed from any front.

If you need more detailed information on squall lines and fronts you may get a better response on earthscience.SE.


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