About WPC's New Probabilistic Winter Precipitation Guidance Web Page

We have made major changes to our probabilistic precipitation web pages for the 2013-14 winter season, both to the user interface and available forecast products.
Summary of the modifications:
User Interface Changes
The user interface can be broken up into three sections (plus the window displaying the forecast). At the top is "Product Selection" (see image below). By default, it will start by displaying 24-hour probability forecasts for snow on Google Maps. Clicking any of these options will automatically switch you to the proper display. Note that for this season we have added 72-hour probability and percentile forecasts.
Product Selection Menu
Regarding the "User Interface" options, we have retained the ability to view GIF images (similar to last years' products). There are advantages and disadvantages of each. Google Maps provides the ability to zoom and pan to where you are interested, as well as change the transparency/opacity of the areas (below the main map are the opacity choices) and overlay the probability or accumulation contours. However, the Google Maps interface loads more slowly than GIF images and cannot easily be printed or imported into other sites. The main disadvantage to GIFs is that they are static images; there is no zooming or panning capability nor can you overlay other fields.

Below the "Product Selection" menu is a horizontal menu bar containing the current product displayed as well as a horizontal line of valid forecast day and time. Aside from the forecast times displayed, this interface is unchanged from last season. In the example below, we are viewing the 24-hour probability of snow exceeding 1 inch for Days 1-3.
Time Line and Product Description
The day and time highlighted in light blue represents the currently-displayed forecast. Change the forecast period by mousing over a different valid day/time.
To the right of the main window are multiple viewing options. There are several new options this year (some are not available when viewing GIFs). They include:
  • Additional forecast times (24- or 48-hour periods)
  • Ability to overlay U.S counties and the probability or percentile accumulation contours (Google Maps only)
  • Ability to toggle the mouse over functionality on or off. This applies to the time line displayed in the menu bar (see above image).
In the future, we will look into adding more overlays for the Google Maps interface.
Viewing Options Menu
Below the main window is a control for the opacity of the displayed forecast. This only applies to the Google Maps interface. By default, the opacity starts at 60%, but you can adjust this up or down depending on how much of the underlying map you wish to view. Higher opacities will hide more of the map (at 100%, no map features are visible), while lower values will show more of the map (at 0%, the forecast is removed).  
Opacity Options
Forecast Product Changes
We've made two notable changes to the product suite. First, we've added 72-hour probability and percentile accumulation forecasts. These cover the entire Day 1-3 period.
Second, we are creating the 24- or 48-hour forecasts in six-hour time steps for Day 1 through 3 (or Day 2 through 3 in the case of 48-hour forecasts). In the example above, you would be viewing a probability of snow exceeding 1 inch valid for the 24-hour period 12Z Wednesday, February 6th, through 12Z Thursday, February 7th. As you move the mouse to the right, you change 24-hour periods by 6 hours at a time. For example, the forecast to the immediate right is the probability of snow exceeding 1 inch for the 24-hour period 18Z Wednesday, February 6th, through 18Z Thursday, February 7th. Move one more and the 24-hour valid period is 00Z Thursday, February 7th, through 00Z Friday, February 8th, and so on. The same principle applies to the 48-hour forecasts.