Air Masses, Fronts, and Frontal Weather
Core knowledge
Know the air mass source regions and classifications (cP, mP, cT, mT, and their continental/maritime variants) and the weather each brings to Canada. Understand front types: cold, warm, stationary, and occluded (cold and warm occlusion). A cold front is steep, fast-moving, with narrow bands of showers, thunderstorms, and a sharp wind veer and temperature drop. A warm front is shallow-sloped, with extensive stratiform cloud, steady precipitation, and a gradual temperature rise. An occluded front forms where a cold front catches a warm front, lifting the warm air aloft.
Know the classic warm-front cloud sequence: cirrus, cirrostratus, altostratus, nimbostratus, stratus, and the associated precipitation belt ahead of the surface front. Cold fronts typically show a narrow cumuliform band at or just behind the front, with rapid clearing behind.
Traps
Questions often reverse the slope and speed characteristics of warm versus cold fronts, or misplace precipitation relative to the front. Another trap: assuming all occlusions produce the same weather. Watch for confusion between the frontal position and the pressure trough.
Rule of thumb
Warm-front precipitation usually precedes the surface front by hundreds of kilometres; cold-front showers are concentrated within tens of kilometres of the front. If a question asks where to expect the steadiest rain, choose ahead of the warm front.