SIGWX chart levels, issuance and mid-level additions
Significant Weather (SIGWX) chart: prognostic chart of hazards, thunderstorms, turbulence, mountain waves, for a flight-level band.
- Issued 12 hr before valid time.
- Valid at 0000Z, 0600Z, 1200Z, 1800Z.
(TC AIM MET 3.1 Table 3.1)
| Version | Levels | Issued by |
|---|---|---|
| Mid-level | FL100 to FL240 (700 to 400 hPa) | Canada's CMACs |
| High-level | FL250 to FL630 | WAFC through US National Weather Service |
Mid-level adds:
- Icing: moderate-to-severe only. Light NOT shown.
- Cloud layers of significance.
- Marked mountain waves.
- Freezing level (0 degrees C) line: every 5 000 ft, labelled in hundreds of feet.
- Surface highs/lows/fronts with direction of motion in knots.
Trap: expecting light icing on mid-level chart. Only moderate-to-severe shown.
References
- TC AIM MET 3.1 Table 3.1
- TC AIM MET 12.2