Rainbands that form near and ahead of cold fronts can be squall lines which can produce tornadoes. The shape of rainbands linked with cold fronts can be changed by mountains. The mountains block the winds which can then form a low-level barrier jet. Bands of thunderstorms can form when sea breeze and land breezes meet, if enough moisture is present. Sometimes sea breeze rainbands which are ahead of a cold front, can hide the location of the cold front itself. Rainbands in an extratropical cyclone can cause large amounts of rain or snow. Behind extratropical cyclones, rainbands can form downwind of large, warmer bodies of water such as the Great Lakes. If the air is cold enough, these rainbands can cause heavy snowfalls.