Dry line symbol

How to read it

NOAA’s Weather Prediction Center defines a dry line as a boundary separating moist and dry air masses, and says it typically lies north to south across the central and southern High Plains in spring and early summer, with moist air from the Gulf of Mexico to the east and dry desert air to the west. Its Unified Surface Analysis Manual draws it as a brown line with scallops facing into the moist air mass. The University of Illinois’s WW2010 guide also calls it a dew point front, and says dry lines are extremely rare east of the Mississippi River.

Both WPC and NOAA’s JetStream school describe a dry line moving east during the day and back west at night.

Also searched as: brown line on a weather map, brown line with scallops, dew point front, dryline.

Differences between charts

Its look varies between charts. WPC’s manual says brown with scallops, and the scallops on its maps are open, not filled. Iowa State University’s surface map guide describes a brown dashed line in one place and a dashed yellow line in another.

Look-alikes

Filled red half circles make a Warm front symbol. The dry line’s scallops are open and brown. An orange dashed line with no scallops is a Trough symbol.