The weak old front that came through with the damaging storms Sunday is still lurking just to our south.  As high humidity comes back Wednesday it's likely what is left of that front will be near us and be the focus of afternoon thunderstorms.  This will be with us Thursday but by late in the week more stable air will come in for a more settled if hot weekend.  With light winds from the south the worst air quality again looks like it will be north of DC and NE of the I-95 corridor