Scaffolded notes
Build the idea
Stationary boundaries can prolong weather
A stationary front forms when neither air mass advances enough to replace the other. Winds often flow roughly parallel to the boundary. Clouds and precipitation can persist or repeat near a stalled front, increasing flood risk if moisture continues arriving.
Occlusion develops in a mature low
An occluded front forms when a faster cold front catches a warm front and lifts much of the warm air away from the surface. It commonly appears near a mature low-pressure system and can produce widespread clouds, wind, and precipitation.
Symbols show type and motion
Blue triangles mark a cold front and point toward its motion. Red semicircles mark a warm front. Alternating symbols on opposite sides show a stationary front; alternating symbols on the same side, usually purple, show an occluded front.
Stop and explain
Check your thinking
1. How are stationary and occluded symbols different?
Possible response: Stationary symbols alternate on opposite sides; occluded symbols alternate on the same side.
2. Why can a stationary front increase flood risk?
Possible response: Lifting and precipitation can persist or repeat over the same area.
Interactive challenge
Try the science
A boundary has red semicircles and blue triangles on opposite sides. What is it?
Before you leave
Exit ticket
Which front would you suspect if rain repeats near the same boundary for two days?