Update the pull request template to include a question about expected…

… impacts to existing METplus Use Cases.

.github/pull_request_template.md

@@ -16,9 +16,12 @@ If **yes**, please describe:</br>
 
 - [ ] Do these changes include sufficient testing updates? **[Yes or No]**
 
-- [ ] Will this PR result in changes to the test suite? **[Yes or No]**</br>
+- [ ] Will this PR result in changes to the MET test suite? **[Yes or No]**</br>
 If **yes**, describe the new output and/or changes to the existing output:</br>
 
+- [ ] Will this PR result in changes to existing METplus Use Cases? **[Yes or No]**</br>
+If **yes**, create a new **Update Truth** [METplus issue](https://github.com/dtcenter/METplus/issues/new/choose) to describe them.
+
 - [ ] Please complete this pull request review by **[Fill in date]**.</br>
 
 ## Pull Request Checklist ##