New Jersey could get a taste of early spring by this weekend, with temperatures expected to rise into the upper 50s and make a run for the low 60s on Saturday. But forecasters say it’s still too early to wave goodbye to winter — with colder air and the potential for snow returning next week. Forecasters from AccuWeather say a “significant shift in the weather across the Midwest and Northeast will be caused by cold air plunging south from Canada and a storm emerging from the Rocky Mountains.” The end result will be colder temperatures returning to New Jersey and other eastern states next week, …