Where to find official turbulence forecasts

The official source: the Aviation Weather Center

In the US, aviation forecasts come from the National Weather Service's Aviation Weather Center at aviationweather.gov. Its Graphical Forecasts for Aviation (GFA) aim to give "a complete picture of the weather that may impact flight in the United States".^1,2

What the products mean

G-AIRMET (Graphical AIRMET)

Graphical advisories of weather that may be hazardous to aircraft but is less severe than in a SIGMET. The turbulence version ("Tango") covers moderate turbulence, sustained strong surface winds and low-level wind shear. AIRMETs cover a six-hour period with a twelve-hour outlook, and over the continental US the graphical versions have replaced text AIRMETs. You can view them in the GFA under Products → G-AIRMET.²

SIGMET

Significant Meteorological Advisory: an advisory for weather that may be hazardous to aircraft, more serious than a G-AIRMET.²

GTG (Graphical Turbulence Guidance)

"Numerical model driven multi-diagnostic turbulence guidance": computer-model forecasts of where turbulence is likely, at different altitudes. It appears in the GFA turbulence tab.²

EDR (Eddy Dissipation Rate)

The scale GTG uses: "an objective measure of turbulence intensity without regard to aircraft characteristics". In other words, it describes the air itself, not how a particular aircraft will feel it.²

PIREPs (pilot reports)

"Reports of actual weather conditions encountered by aircraft", including turbulence. They're also shown on the GFA map.²

Reading the map without worrying

• Forecast areas show where turbulence may occur, and GTG forecasts vary by altitude. A colored area on the map doesn't mean every flight through it will be bumpy.
• The seat belt sign is often turned on as a precaution before expected bumps. Keep your belt fastened whenever you're seated.³