I am local to this case and drove around the area this morning.
Map attached. A- Adam's Farm condos, W-Williamsburg condos, S- Southwell Field,
1) Kennedy Drive (Adam's Farm Condominiums) where Susan lives. No police presence. Only saw one missing persons flyer, just on her residence.
2) Wellman Ave (Williamsbug Condominiums), sprawling complex on the Merrimack River where heavy LE presence was seen on Monday during a day of searching. No police presence today, and no flyers observed. We don't know Susan's connection to Williamsburg, but obviously there is one.
It is one mile from Adam's Farm to Williamsburg. Three ways to get there on foot, by the busy main road which doesn't have sidewalk the entire way, on the RR tracks that run by both places, or by paths going by the Southwell baseball fields near the river, these paths lead to Williamsburg and is the shortest route by foot.
I also drove down the windy road to the Southwell field boat ramp, which is close to Susan's condo and in between the two condo's. The boat ramp road was unplowed and had an inch or two of tire packed snow. It hasn't snowed since Susan's disappearance. Two sets of tire tracks were backed up to the boat ramp near the water, one small set directly up to the water, and one much larger set about ten feet back. The Merrimack River has a perimeter of thin crusty ice, such that you can't just walk into the water. At the end of the boat ramp, the ice was broken and refrozen out to a distance of 15 feet, then it wasn't broken, as if someone had broken the ice and walked into the water, maybe up to their waist or more (image attached). I doubt it was caused by any type of boat launch. Just an observation and not making anything of it, I'm sure LE was in the area during their search, and it might well have been LE that went into the water.
Susan was reportedly last seen by a neighbor on the morning on December 20th, possibly "confused"- although we don't know who said this. This description leads us down the path to think she went missing that morning, while she was on this walk.
We shouldn't assume that.
She could have returned home and disappeared hours later. When was she reported missing and by whom?