How can a small manufacturer model cash flow with seasonality and capex?

[Donald66]

I run a small manufacturing business, and while I have a basic handle on my monthly cash flow forecasting, I'm constantly caught off guard by seasonal dips in receivables and unexpected capital expenditures for equipment repairs, which creates stressful cash crunches that threaten our ability to meet payroll. My current forecast is essentially a static spreadsheet based on last year's numbers, and it fails to account for the variability in client payment terms or the impact of taking on larger, slower-paying projects. For other small business owners, what tools or methodologies have you adopted to create a more dynamic and accurate cash flow forecast? How do you model different scenarios, like a major client delaying payment or a sudden opportunity requiring upfront inventory investment, and what key performance indicators do you monitor weekly to give you an early warning of potential shortfalls?