<div id="notificationsTile">
    <div class="blue">
       <div class="step">
            <ul ng-repeat="item in Model.DisplayNotifications">
                <li itemPriority = {{item.Priority}}>
                    <h3>{{ item.EndDate | date: 'dd MMMM' }}</h3>
                    <p>{{ item.NotificationName }}</p>
                </li>
            </ul>
        </div>
    </div>
</div>

scope.$watch("itemPriority", function(newVal, oldVal){
                debugger;
            });

notificationsTileModule.directive('spNotificationsTile', function (spNotificationsService, spSessionStorageService) {
    return {
        restrict: 'E',
        replace: true,
    scope: {
            priority: '=itemPriority'
        },
        templateUrl: '/_catalogs/masterpage/SPDP.Portal/Views/NotificationTile/NotificationTile.html',
        link: function (scope, element, attrs) {

            var model = scope.Model = {
                DisplayNotifications: []

            };

            //model.Priority = scope.itemPriority;

            scope.$watch('priority', function(newVal, oldVal){
                debugger;
            });
}
});

<ul ng-repeat="item in Model.DisplayNotifications">
    <li item-priority="item.priority">{{item.priority}}
    </li>
</ul>

app.directive('itemPriority', function() {
  return {
    restrict: 'A',
    scope: {
      priority: '=itemPriority'
    },
    link: function(scope, element, attr) {
      scope.$watch('priority', function() {
        console.log(scope.priority);
      });
    }
  }
});

<ul ng-repeat="item in Model.DisplayNotifications">
  <li>
    <div ng-class="{'alert-danger': item.priority < 2,
        'alert-warning': item.priority >= 2 && item.priority < 4,
        'alert-info': item.priority >= 4}">
      {{item.priority}}
    </div>
  </li>
</ul>

<div sp-notifications-tile items="Model.DisplayNotifications" class="alert">
  <ul>
    <li ng-repeat="item in Model.DisplayNotifications">
...

app.directive('spNotificationsTile', function() {
  return {
    restrict: 'A',
    scope: {
      items: '='
    },
    link: function(scope, element, attr) {
      scope.$watch('items', function() {
        var firstItem = element.find('li')[0];
        var firstPriority = angular.element(firstItem).scope().item.priority;

        if (firstPriority > 3)
          element.addClass('alert-warning');
        else
          element.removeClass('alert-warning');
      }, true);
    }
  }
})

$scope.itemPriority = item.Priority ;


scope.$watch('itemPriority ', function( status )
  {
   console.log(status);
 });