When the 
button
is pressed, the GFE is put into the ISC (intersite coordination)
mode.
The data viewed in the spatial editor will be the composite of your
forecast
data and the adjacent received site's data. Certain edit tools,
such
as Pencil, also work different in ISC mode. The data values are
picked
up may be either from your forecast grid or from the intersite
coordination
grid depending upon the location on the grid.
Try placing the GFE into ISC mode and observe how the display changes. You may have observed that the entire grid is no longer pictured. If so, this means that data is not available from all of your surrounding sites. Note also that your forecast grid is clipped to your CWA. Use the Sample Tool and note that when you sample outside your area that the samples will now shown an update time and site identifier from the ISC sites (if those features are enabled).
Try using the Pencil Tool and Move/Copy tool to change some data. Note that it uses the values from the composite grid for its operation, but you may not see the entire data change. Since only a portion of your forecast grid is shown (just those parts within your CWA), changes you make to portions of your grid outside your CWA will not be seen while in ISC mode. Toggle off ISC mode to see your entire forecast grid.
Markers (similar to samples) may appear, which represent one
location
per adjacent grid. The markers may be set up to display the last
grid update time, the WFO identifier, and whether the ISC data was
published
or is the working grid.
While most of the weather elements simply are masked so that you see
your Fcst database within your CWA, and the ISC data outside your CWA,
some ISC elements are calculated on-the-fly. For example, the QFP
weather element for ISC is a virtual, as shown with the VISC label in
the spatial editor legend. There is a QPF ISC element, and a
virtual QPF ISC element. The virtual element is the summation of
all of the "precipitation rates" and is valid the same time period as
the Forecast grid.
Refer to the Intersite Coordination Guide
for
more details.