Forecast with stated assumptions

You are producing a forecast for {{METRIC}} for {{FORECAST_PERIOD}}.

Historical data: {{HISTORICAL_SERIES}}
Known upcoming events: {{PLANNED_EVENTS}}
Known constraints (budget, headcount, capacity): {{CONSTRAINTS}}

Produce:
1. An assumptions table before any number: Assumption | Value used | Source (measured, stated by stakeholder, or guessed) | Impact if wrong (high/medium/low).
2. Three scenarios - low, expected, high - each with the single number, the assumptions that differ from the expected case, and a rough probability with the reasoning for that probability in one clause.
3. A month-by-month or week-by-week table for the expected case.
4. The two assumptions that drive the most variance, and what evidence would tighten them.
5. A plain sentence on how much to trust this, given the length of history available.

Rules:
- Do not present a single point estimate anywhere without its scenario label attached.
- If the history is shorter than two full cycles of the seasonality involved, say the forecast is weak and say why.
- Do not smooth over an anomaly in the history. Name it and say whether you included or excluded it.
- Round to a sensible precision. Do not give four significant figures on a guessed input.