Before checking out for the night, I just checked the tide charts for Grand Isle, LA. A high tide is expected somewhere around 7am local time (depends whose chart you believe) on Monday morning. This is projected to be within a few hours of landfall. The good news (?) is that the tidal differential is relatively minor here -- about 1.4 feet.
I suppose if you're buried under a 20-foot+ storm surge, another 17 inches won't matter much, but it'll add to the problems.