These 3 charts offer clues to what might happen next in Mass. coronavirus pandemic

A person was tested for the coronavirus. The state has been reporting fewer positive cases. What's next?John Tlumacki/Globe Staff

The pandemic appears to be on the decline in Massachusetts. So what’s next? Three charts offer clues.

An ensemble model developed by the University of Massachusetts Amherst foresees declining cases in the next four weeks.

The latest version of the model, issued Tuesday, predicts that by March 20 the number of confirmed and probable cases per week will drop to 6,488 (though researchers note the numbers could range higher or lower).

That’s sharply down from 42,954 per week at the peak of the state’s second surge around the beginning of the year.

The model from the lab of Nicholas Reich combines multiple models and projects cases and deaths for four weeks.

A UMass model predicts COVID cases will continue to decline for the next four weeks.Reich Lab/UMass

Meanwhile, tests for the coronavirus in the wastewater at the Massachusetts Water Resources Authority plant at Deer Island show a sharp decline from peak levels. But the levels haven’t returned yet to the levels of the summer, and they’re wavering, with slight upticks and downticks in recent days.

The pilot program looks for SARS-CoV-2 RNA copies per milliliter of wastewater. Officials are hoping that the tests can serve as an early warning system for virus surges. Cambridge-based Biobot Analytics, which conducts the testing, says it has found that the amount of virus in the wastewater is correlated with newly diagnosed coronavirus cases four to 10 days later. The company also says its tests can detect both the current version of the virus and variants.

Results are shown for both the northern and southern sections of the MWRA system. Boston, the state’s largest city, is included in the northern section.

A third chart offers less of a forecast and more a reminder about the wild card in the equation. Experts have warned about the possibility of a new surge fueled by the arrival of fast-spreading coronavirus variants in the United States from other countries. The looming threat, they say, underlines the importance of the coronavirus vaccination campaign underway.

This third chart shows how Massachusetts and other states are doing in terms of the number of coronavirus variant cases detected here so far. Experts say the numbers are likely undercounts due to insufficient testing capability.