1. Weather Maps -- A weather chart drawn for a given level (e.g., sealevel or surface or at 18000 feet, for examples).
   
   
2. Pressure Systems That Can Appear On Weather Maps
   1. Low Pressure Areas--
      1. Cyclone -- an area of low pressure completely encircled by at least one isobar (analogy: Tahoe Valley)
      2. Trough -- an area of low pressure not completely encircled by at least one isobar (analogy: a ravine)
   2. High Pressure Areas --
      1. Anticyclone -- an area of high pressure completely encircled by at least one isobar (analogy: mountain peak)
      2. Ridge -- an area of high pressure not completely encircled by at least one isobar (analogy: a mountain ridge)