As of late Monday, the city’s official snow depth had shrunk by 6 inches since its peak at 21 inches one week ago. Much of this has been due to compaction of the snow under its own weight. Limited melting has also caused some erosion as daytime temps crept above freezing Sunday and Monday. More substantial melting is to begin Tuesday. The combination of generous sunshine and an influx of mild air from the Plains is forecast to raise temps to the low and mid-40s. High temps upstream over South Dakota topped 60 degrees Monday afternoon. As this mild air encounters deeper snow cover over the Midwest, warming will be tempered, but readings are still expected to be the highest observed here since Dec. 27. Snow cover to our south and west has rapidly receded. National snow cover stood at 47% Monday morning.