Keep selected edit status

Question

Colleagues.

I have a registration form from which the user when choosing the state, automatically appears the city. But I would like in the edition, the city already appeared selected. The code I have is this:

<div class="item form-group">
                      <label class="control-label col-md-3 col-sm-3 col-xs-12" for="">Estado: <span class="required">*</span>
                      </label>
                      <div class="col-md-6 col-sm-6 col-xs-12">
                        <?php echo $metodos->listarEstados($visualizar->Estados); ?>
                      </div>
                    </div>                   
                      <div class="item form-group">
                      <label class="control-label col-md-3 col-sm-3 col-xs-12" for="">Cidade: <span class="required">*</span>
                      </label>
                      <div class="col-md-6 col-sm-6 col-xs-12">
                        <!--<span class="carregando">Aguarde, carregando...</span>-->
                        <select name="Cidades" class="select2_single form-control" id="cidades">              
                </select>
</div>

Jquery

$(function(){
    $("#estados").change(function(){
     var id = $(this).val();
     // var id = <?php echo $visualizar->Cidades; ?>;
        $.ajax({
            type:"POST",
            url:"exibe-cidades.php?id="+id,                    
            dataType:"text",
        success: function(res){                      
            $("#cidades").children(".cidades").remove();
            $("#cidades").append(res);
         }
      });
    });
  }); 

city displays.php

header( 'Cache-Control: no-cache' );
    header( 'Content-type: application/xml; charset="utf-8"', true );
      include("conexao.php");
    $id = $_GET['id'];
        $sql = mysqli_query($conexao, "SELECT * FROM crm_cidades WHERE estados_cod_estados='$id' ORDER BY nome");
        while($row=mysqli_fetch_array($sql)){
              $nome=$row['nome'];
              $id=$row['cod_cidades'];
              echo '<option value="'.$id.'" class="cidades">'.utf8_encode($nome).'</option>';
        }