Snow ensemble "analysis" and recentering

[CoryMartin-NOAA]

What new functionality do you need?

Need to initialize the ensemble forecast members based on the deterministic snow analysis and the background ensemble spread.

What are the requirements for the new functionality?

Regridding, recentering, and analysis increment applied to states

Acceptance Criteria

updated test that passes that includes snow DA with the ensemble

Suggest a solution (optional)

I'll take care of it :-)