FIS-B weather is useful. It is not live radar.

Know what is arriving

FIS-B sends selected weather and aeronautical products over the UAT link. Receiving ADS-B traffic does not, by itself, establish that weather products are arriving. Product availability also depends on the receiver and display. See the FAA ADS-B In application guide for the service and its limitations.

Read the product, not just the connection light

Use a short ground check before the flight:

• Identify the actual weather source: downloaded internet data, receiver broadcast data, or another source.
• Open the desired product and inspect its timestamp and coverage. A connected receiver may not yet have supplied that product.
• Understand which age the display is reporting. A receiving time and an observation or radar-generation time are different things.
• Check what the screen shows when data is absent. Do not interpret a blank radar area as proof of clear weather.

Why weather can lag the screen

The FAA warns that cockpit broadcast weather is intended for planning decisions, not tactical maneuvering around localized weather. Radar processing and distribution introduce delay; the apparent age on a display need not represent the full age of the underlying weather. The AIM surveillance section also explains that reception depends on line of sight and service volume. Low-level or ground reception can therefore differ from reception aloft.

Write a fallback before you need it

In your own briefing notes, answer: “If this product stops updating, what will I stop assuming?” and “Where will I obtain an appropriate update?” Discuss that plan with your instructor as needed. This keeps receiver troubleshooting from becoming the main task during a busy phase of flight.

FLAL and completeness

FLAL can display supported receiver products, but no connection label guarantees complete weather coverage. Its available TFR and advisory material is not a complete NOTAM briefing. Complete the official preflight briefing separately, then review dates and data age throughout the trip. More colored layers do not necessarily mean a more current picture.