Black Ice and Fog Require Extra Wednesday AM Caution for Boston Area Through New Hampshire, Maine Coastline

Though all eyes are on the record warmth across the majority of the Lower 48, and spilling into New England, there is a subtle but very important feature in the Gulf of Maine that poses a travel headache for Eastern New England - including the Boston area - Wednesday morning.  That feature is a small area of low pressure - a small scale storm center - off the Maine coastline.  Because wind turns counter-clockwise around storm center, this has prompted a northeast wind in the wake of the small storm, meaning a surge of cold air pressed southward through Southeast New Hampshire and Eastern Massachusetts Tuesday night.  Of course, this surge of cold comes at the same time the large-scale weather pattern favors carrying warmth into New England, as was evidenced by record-warm high temperatures for some on Tuesday afternoon.  The collision of warmth moving northward, and cold moving southward, creates a swath of cool but moist air in Eastern Massachusetts through Southeast New Hampshire into Southern and coastal Maine Monday night through early Tuesday morning, resulting in two phenomena: 1) fog, and 2) black ice.  Though both will occur in pockets, the former can be quite dense in this type of setup, restricting visibility for drivers, and the latter can require road treatment, though rock salt should do the trick for most spots.  Nonetheless, I'd encourage caution and extra time for the Wednesday morning drive - especially early commuters - in these eastern areas.