Reading GFAs for the INRAT Exam

GFA interpretation is one of the areas where candidates lose the most marks on the meteorology section — not because the charts are hard to read, but because most people try to learn them from text descriptions instead of actual charts. By the time exam day arrives, they've never worked through a real GFA. That's fixable.

What a GFA is

A Graphical Area Forecast is a weather forecast product issued by NAV CANADA. It covers clouds and weather conditions across large geographic areas of Canada and is one of the primary forecast tools for IFR flight planning. The INRAT tests your ability to read and interpret GFAs — not just know what they are.

GFAs are issued four times daily and cover a 12-hour valid period with a 6-hour outlook. They come in two panels:

• Clouds and Weather (CLD&WX): Cloud layers, ceilings, visibility, precipitation, and significant weather
• Icing, Turbulence, and Freezing Level (ICG/TURB/FZLVL): Icing conditions, turbulence, and the freezing level contours

Reading the clouds and weather panel

The CLD&WX panel uses scalloped lines to outline areas of similar weather. Inside each area, you'll find encoded information about cloud layers, tops, bases, and any significant weather like rain, snow, or fog.

Cloud encoding

Clouds are described with coverage (FEW, SCT, BKN, OVC), height in hundreds of feet AGL, and tops where relevant. A line like BKN 030 TOP 080 means broken clouds with a base at 3,000 feet AGL and tops at 8,000 feet.

Visibility and weather

Visibility is given in statute miles. Weather abbreviations follow standard METAR/TAF conventions — RA for rain, SN for snow, BR for mist, FG for fog. When visibility drops below 6 SM, it's noted explicitly.

Reading the icing and turbulence panel

The ICG/TURB/FZLVL panel shows freezing level contours as dashed lines labeled in hundreds of feet MSL. Where the freezing level is at the surface, it's labeled SFC. Above the surface, contours indicate where 0°C occurs.

Icing areas are outlined and described by intensity (trace, light, moderate, severe) and type (rime, clear, mixed). Turbulence is noted similarly, with intensity and altitude range.

Where candidates go wrong

The most common mistake is confusing AGL and MSL heights. Cloud bases on the CLD&WX panel are in feet AGL. Freezing levels on the ICG panel are in feet MSL. This matters in mountainous terrain — a freezing level at 4,000 MSL over terrain at 3,500 feet means the freezing level is only 500 feet above ground, not 4,000.

The second mistake is misreading the valid time. A GFA has a valid period and a separate outlook period. Questions will specify which period to reference. Reading the wrong time means interpreting the wrong weather picture.

How GFA questions are structured on the exam

Questions typically give you a GFA excerpt or description and ask what conditions a pilot would encounter along a specific route or at a specific altitude. Some questions ask about a single panel; others require combining information from both panels — for example, identifying whether icing is likely at a given altitude by cross-referencing cloud tops with the freezing level.

This is one of the 13 INRAT categories where the TP 691E alone won't prepare you. The guide explains the format well. Interpreting charts under time pressure is a separate skill that only comes from practice.