Most of the extended hourly forecasts I see have the rain predominantly stopping around dinnertime on Friday. The trouble is that the temps are going to be plunging around the same time so if the water from the rain isn't off the roadway before the temps get too low, it can make a mess of things.

Your best bet - wake up extra early and hit up ctroads.org to check out the status of the roads. You can even get access to the highway cameras. Also do a Google Maps direction search from your home to LGA to get a rough estimate of travel time. I find Google Maps tends to be pretty good because they try to take traffic conditions into account.