Definition
An FAA Advisory Circular that explains the aviation weather products available to pilots, including how each product is created, what it shows, how to read it, and how to use it for flight planning and in-flight decisions. It is the FAA's official reference guide to weather reports, forecasts, charts, and observations used in U.S. aviation.
Plain English
AC 00-45 is the FAA's user manual for aviation weather products. If you want to know what a weather chart, report, or forecast means and how to use it, this is the document the FAA points you to.
Context Anchor
Seen in FAA handbooks and training material when the text points pilots to a more detailed source for aviation weather products and hazards.
Derivation
"AC" stands for Advisory Circular, the FAA's series of guidance documents that explain how to apply regulations and procedures. The number "00-45" identifies this specific circular within that series. Numbers in the 00 range cover general subjects, and 45 is the slot assigned to aviation weather services.
Why Pilots Care
It identifies the exact weather products pilots must consult before and during flight to avoid volcanic ash and other hazards.
Intuition Check
AC here does not mean air conditioning or alternating current. In this FAA context, AC means Advisory Circular, a guidance document.
Example Sentence 1
When the student asked what the symbols on the prognostic chart meant, the instructor pulled up AC 00-45 and walked through the legend.
Example Sentence 2
Before the cross-country flight the instructor had the student review AC 00-45 for the latest aviation weather service updates.