A similar phenomenon to a weather front is the dry line, which is the boundary between air masses with significant moisture differences. When the westerlies increase on the north side of surface highs, areas of lowered pressure will form downwind of north–south oriented mountain chains, leading to the formation of a lee trough. Near the surface during daylight hours, warm moist air is denser than dry air of greater temperature, and thus the warm moist air wedges under the drier air like a cold front. At higher altitudes, the warm moist air is less dense than the dry air and the boundary slope reverses. In the vicinity of the reversal aloft, severe weather is possible, especially when a triple point is formed with a cold front. A weaker form of the dry line seen more commonly is the lee trough, which displays weaker differences in moisture. When moisture pools along the boundary during the warm season, it can be the focus of diurnal thunderstorms.
The dry line may occur anywhere on earth in regions intermediate between desert areas and warm seas. The southern plains west of the Mississippi River in the United States are a particularly favored location. The dry line normally moves eastward during the day and westward at night. A dry line is depicted on National Weather Service (NWS) surface analyses as an orange line with scallops facing into the moist sector. Dry lines are one of the few surface fronts where the pips indicated do not necessarily reflect the direction of motion.
... In the dry sector west of the dry line, clear skies are the rule due to the dryness of the air mass sweeping off the Rocky mountains in North America, and the ... Cumulus clouds are common east of the dry line in the moist sector, though they are taller with greater development along the dry line itself ...
... were always faced with the possibility of it going dry, especially in the summer months ... the mill was later transferred to the Davault Bollinger line ... It connected the old Cape Girardeau and State Line properties with the Iron Mountain Line at Delta ...
... AND 100 STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH NORTHWEST OF BROKEN BOW NEBRASKA TO 55 MILES SOUTHWEST OF RUSSELL KANSAS ... WITH LITTLE INHIBITION REMAINING ALONG E OF DRY LINE...STORMS WILL RAPIDLY BECOME SEVERE BY EARLY THIS AFTERNOON WRN KS INTO SWRN NEB ... AS DRY LINE REMAINS WRN KS THRU THE AFTERNOON...ADDITIONAL DEVELOPMENT OF TORNADIC SUPERCELLS ARE LIKELY OFF THE DRY LINE THRU THE EVENING HOURS ...
... air across Texas and into western Oklahoma and dry line formed across the Texas panhandle ... Later that day, the low clouds broke as predicted by forecasters as the dry line moved east into western Oklahoma ... However, the clearing was limited to a relatively narrow zone ahead of the dry line ...
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