When does a warm front occur?

<p style=";text-align:left;direction:ltr">Arab Weather - A warm air front occurs when a warm air mass moves towards a cold air mass. As the warm front advances, the warm mass rises above the cold mass because the warm air is less dense. This leads to cloud formation and precipitation, and the precipitation is often light to moderate and lasts longer than a cold air front.</p><p style=";text-align:left;direction:ltr"> The sky is mostly cloudy, and as the front passes, temperatures gradually rise and the weather improves after the front passes.</p>