This guide walks you through the steps to create a new forecast in your HEC-RTS watershed.

Prerequisites

Before creating a forecast, ensure that model alternatives and forecast runs are already defined. If needed, refer to the appropriate tutorials for setup guidance.

Step 1: Open the Create New Forecast Dialog

  1. Launch HEC-RTS and open your watershed.
  2. Go to the Modeling tab.
  3. From the Forecast menu, select New.
  4. The Create New Forecast dialog will open.

Step 2: Select a Forecast Type

The Select Type dropdown defaults to New Forecast. 

  1. Choose the appropriate option from the dropdown:
    1. New Forecast - Create a new forecast (default).
    2. From Existing Forecast - Copy the Time Window settings and selected Forecast Run(s) from an existing forecast.
    3. From Archived Forecast - Copy the Time Window settings and selected Forecast Run(s) from an archived forecast.
    4. From Imported Forecast - Copy the Time Window settings and selected Forecast Run(s) from a forecast file stored to disk.
The remainder of the guide assumes you are choosing New Forecast during this step. The dialog will change depending on your choice.

Step 3: Define the Time Window

  1. Set the Forecast Time (defaults to current date/time). 
  2. Adjust the Extract Start, Start Time, and End Time as needed.
    1. These are set using the default time window settings. See the section below to edit the settings, if needed.

These times determine the simulation window. Ensure they:

  • Cover enough time before the forecast to support flow routing and model calibration.
  • Allow sufficient time for loss rate calibration in HEC-HMS.

Typically, the Start Time and Extract Start are the same, but may differ depending on modeling needs (e.g., updating a forecast later in the day).

Optional: Adjust Default Time Window Settings

To change default time window settings:

  1. Go to the Modeling tab.
  2. From the Forecast menu, select Default Time Window.
  3. Edit the:
    1. Extract Period 
    2. Look Back Period 
    3. Forecast Length 
  4. To align start/end times to midnight, check Default Lookback/End times to start/end of day.

Step 4: (Optional) Rename the Forecast

HEC-RTS automatically generates a forecast name based on the forecast time.

To rename:

  1. Enter a new name in the Name field.
  2. Optionally, include a Description.

Step 5: Select Forecast Runs to Include

Now, select the forecast runs you wish to include in the forecast from the table at the bottom of the dialog. 

  1. Check the box(es) in the Selected column to include one ore more forecast runs. 

Step 6: Create the Forecast

  1. Review your time window and forecast run selection. 
  2. Click OK to create the forecast.
  3. A Progress window will appear, showing status updates during the process. (You can also monitor progress via the Messages tab.)

Final Review

Once the forecast is created, it will load in the Modeling tab and the model schematic will appear in the map window.