Switch APCP_surface to sum

[mattw-nws]

Use weighted_sum instead of weighted_mean for APCP_surface

Additions

• Also added venv and .venv to .gitignore

Removals

-

Changes

• Use weighted_sum instead of weighted_mean for APCP_surface

Testing

1.

Screenshots

Notes

-

Todos

-

Checklist

• [X] PR has an informative and human-readable title
• [X] Changes are limited to a single goal (no scope creep)
• [X] Code can be automatically merged (no conflicts)
• [X] Code follows project standards (link if applicable)
• [X] Passes all existing automated tests
• [X] Any change in functionality is tested
• [X] New functions are documented (with a description, list of inputs, and expected output)
• [X] Placeholder code is flagged / future todos are captured in comments
• [X] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• [X] Reviewers requested with the Reviewers tool :arrow_right:

Testing checklist

Target Environment support

• [X] Linux

[mattw-nws]

Actually uncertain if we don't want mean and sum for the stat instead of the weighted version. Also this didn't make me get non-zero values where I thought it might.