I think it really depends on low tonite and how long it remains.If 30, then shouldn't be that hard of a freeze and soon as temps hit 33 tomorrow, melt is on.If temps get to below 32 for a good while then ice is thicker and will take longer to melt.
Hopefully temps don't stay below 32 for more than 6 hrs or so overnight.
Apple Weather on my iPhone says Gretna temperatures will stay 28F and below for about 11 hours (~8 p.m. - ~7 a.m.) with an overnight low of 25F. Note that they missed high on last night's overnight low by several degrees.
Weather Underground for Gretna shows roughly the same thing, but a little more sustained and a lower low temp -- 29F and below for about 13 hours (~6 p.m. - ~7 a.m.) with an overnight low of 22F.