How to flip LTspice voltage controlled switch so that it opens at threshold voltage? (versus close)
From the LTSpice help file:

Symbol Names: SW
Syntax: Sxxx n1 n2 nc+ nc-  [on,off]
Example:
S1 out 0 in 0 MySwitch
.model MySwitch SW(Ron=.1 Roff=1Meg Vt=0 Vh=-.5 Lser=10n Vser=.6)

The voltage between nodes nc+ and nc- controls the switch's impedance between nodes n1 and n2. A model card is required to define the behavior of the switch.

So if you switch the connections to the nc+ and nc- pins and invert (multiply by -1) the Vt value, you should get the effect you want.