From the high ground in west Methuen you can watch weather cross the Merrimack valley a full hour before it arrives, which turns out to be a useful habit in this trade. Xcel Landscape Design & Hardscape Inc. works both ends of that forecast: lawns mowed, trimmed and edged through the green months, cleanups that clear leaves off before the first hard freeze. Then come the plows — driveways and walkways opened early, pavement taken down clean, the storm answered while it is still dark out. What ties the two halves together is one eye for line: a lawn with a defined edge, a driveway cleared to its true width. Yards here sit close enough together that neatness reads the whole way down a block.