Using a for loop to write multiple formulaic if statements

I have a chain of if statements that control the opacity of an image depending on the .scrollTop() of the page. Here are the rather unsightly chain of if statements:

if (wScroll > 180) {
    $(".coffee").css("opacity", 1);
  }
  else if (wScroll <= 180 && wScroll > 162) {
    $(".coffee").css("opacity", 0.9);
  }
  else if (wScroll <= 162 && wScroll > 144) {
    $(".coffee").css("opacity", 0.8);
  }
  else if (wScroll <= 144 && wScroll > 126) {
    $(".coffee").css("opacity", 0.7);
  }
  else if (wScroll <= 126 && wScroll > 108) {
    $(".coffee").css("opacity", 0.6);
  }
  else if (wScroll <= 108 && wScroll > 90) {
    $(".coffee").css("opacity", 0.5);
  }
  else if (wScroll <= 90 && wScroll > 72) {
    $(".coffee").css("opacity", 0.4);
  }
  else if (wScroll <= 72 && wScroll > 54) {
    $(".coffee").css("opacity", 0.3);
  }
  else if (wScroll <= 54 && wScroll > 36) {
    $(".coffee").css("opacity", 0.2);
  }
  else if (wScroll <= 36 && wScroll > 18) {
    $(".coffee").css("opacity", 0.1);
  }
  else if (wScroll <= 18) {
    $(".coffee").css("opacity", 0);
  }

I would like to condense these down into a for loop. My attempt at it only works when scrolling down (adding opacity) but not when scrolling up (subtracting opacity). Sometimes it doesn't work at all. This is what I have come up with:

var lessThanEqualTo = 18;
var greaterThan = 0;
var inc = 18;
var opacityVal = 0;

$(window).scroll(function() {
  var wScroll = Math.round($(this).scrollTop());
  var count = 0;

  if (wScroll > 1) {
    for (var i = 0; i < 10; i++) {
      var opacity = $(".coffee").css("opacity", (opacityVal/10));
      if (wScroll <= lessThanEqualTo && wScroll > greaterThan) {
        opacity;
        opacityVal++;
        lessThanEqualTo += inc;
        greaterThan += inc;
      }
    }
  }

  $(".coffee").css({
    "transform" : "translate(0px," + wScroll/1.5 + "%)"
  });

});

Any help or advice on this would really be helpful.