Per #1644, add a few sentences to Point-Stat, Practical Information c…

…hapter about debugging 0 matched pairs.

met/docs/Users_Guide/point-stat.rst

@@ -252,6 +252,8 @@ _____________________
 
 The Point-Stat tool is used to perform verification of a gridded model field using point observations. The gridded model field to be verified must be in one of the supported file formats. The point observations must be formatted as the NetCDF output of the point reformatting tools described in :numref:`reformat_point`. The Point-Stat tool provides the capability of interpolating the gridded forecast data to the observation points using a variety of methods as described in :numref:`matching-methods`. The Point-Stat tool computes a number of continuous statistics on the matched pair data as well as discrete statistics once the matched pair data have been thresholded.
 
+If no matched pairs are found for a particular verification task, a report listing counts for reasons why the observations were not used is written to the log output at the default verbosity level of 2. If matched pairs are found, this report is written at verbosity level 3. Inspecting these rejection reason counts is the first step in determining why Point-Stat found no matched pairs. The order of the log messages matches the order in which the processing logic is applied. Start from the last log message and work your way up, considering each of the non-zero rejection reason counts.
+
 point_stat usage
 ~~~~~~~~~~~~~~~~