Describe the bug

When snow model is enabled in pvwattsv8, DC snow loss = 0 for time steps with snow loss:

And, DC snow loss = 1 for time steps with gen > 0, regardless of whether the snow model is enabled:

To Reproduce

1. Create a PVWatts / No Financial case.
2. Change the weather file to Fargo, ND (legacy TMY2 file with snow data).
3. Click Simulate.
4. Note DC power loss due to snow (%) value of 1 for time steps with System power generated (kW) > 0 (and some sunup or sundown time steps).
5. On System Design page, expand Advanced Inputs panel and check Estimate snow losses.
6. Click Simulate.
7. Note gen = 0 for first few days, but DC snow loss = 0, also true for Feb 1 when next snow event occurs.

Expected behavior

Expect DC power loss due to snow to be a percentage of the array DC output, such as 100% when snow completely covers the module at the beginning of a snow event.

Operating System and Version

• OS: Windows 10
• Version: SAM 2021.12.02 r2