The kind of front that usually forms long, thin stratus clouds is a warm front.

Here's why:

* Warm fronts are characterized by a warm air mass pushing a cold air mass.

* As the warm air rises over the colder air, it cools and condenses, forming stratus clouds.

* The slow, gradual lifting of the warm air results in the formation of broad, sheet-like stratus clouds, which can stretch for long distances.

While other fronts can produce stratus clouds, warm fronts are most closely associated with the formation of the long, thin stratus clouds you describe.