A forecast revised at declared checkpoints as actual cost, delivery evidence and changed assumptions become available, while preserving the basis of earlier versions.

# Rolling-wave forecast

A rolling-wave forecast replaces one permanently correct prediction with a controlled sequence of estimates. Each version records what was known, what changed and which decision the evidence should alter.

It is not permission to move a date without consequence. Where a contract, regulation or external event fixes a deadline, the forecast should expose which scope, funding or risk decision must change.

## Sources

- gao-cost-estimating-guide-2020 (primary)
- scrum-guide-2020 (canonical)