Increase the number of variations loaded in the WooCommerce front end for dynamic filtering of available variations in the drop down lists.

increase-variation-threshold.php

<?php //only copy this line if needed

/**
 * Function filters the threshold for the amount of variables to load in the front end.
 *
 * @see 	https://woocommerce.wordpress.com/2015/07/13/improving-the-variations-interface-in-2-4/  
 * @param   	int 	$threshold 	Default of 30
 * @return 	int 	100 		The new threshold.
 */
function lets_increase_the_variation_threshold( $threshold ) {

	return 100;
}
add_filter( 'woocommerce_ajax_variation_threshold', 'lets_increase_the_variation_threshold' );