There are those who now question whether the lower half of Minnesota will experience any sub-zero weather the rest of this winter.  Another warm front moves in over the state today (MON) and forecasters predict highs near 50 in southern Minnesota — possibly even warmer on Tuesday.  Even northern Minnesota will likely stay 20 degrees above normal until mid-week.  After that, however, much colder air will sail into Minnesota, bringing a chance that the mercury will dip below zero.  By the way, there’s never been a Minnesota winter when the temperature didn’t go below zero at least twice.