![]() (Blowing dust and rising temperatures also may follow, especially if the dry line passes during the daytime.) These changes occur in reverse order when the dry line retreats westward. However, a strong storm system can sweep the dry line eastward into the Mississippi Valley, or even further east, regardless of the time of day.Ī typical dry line passage results in a sharp drop in humidity, a rise in temperatures, clearing skies, and a wind shift from south or southeasterly to west or southwesterly. The dry line typically advances eastward during the afternoon and retreats westward at night. It typically lies north-south across the central and southern high Plains states during the spring and early summer, where it separates moist air from the Gulf of Mexico (to the east) and dry desert air from the southwestern states (to the west). Occluded Frontĭry air, being more dense, undercuts the light moist air forcing it up.Ī dry line marks the boundary between a moist air mass and dry air mass. The difference in temperature and wind direction from one side of a stationary front to the other is generally not large but there can be times where the difference is stark. A stationary front is depicted by an alternating red and blue line with a triangle on the blue portion and half-moon on the opposite side of the red portion of the line.Ī cold front (or warm front) that stops moving becomes a stationary front. the two air masses on either side are not moving perpendicular to the front) it is called a stationary front. If the front is essentially not moving (i.e. After the rain ends and the front passes, winds shift to the northwest and temperatures fall into the 40s and skies clear. A few hours later, a line of thunderstorms sweeps across the area just ahead of the cold front. Temperatures are in the 50s with winds from the east.Īs the warm front passes, the rain ends, skies become partly cloudy and temperatures warm into the mid 70s. Here is an example of a location that experiences typical warm frontal passage followed by a cold frontal passage: Clouds lower and thicken as the warm front approaches with several hours of light to moderate rain. Like cold front, warm fronts also extend from the center of low-pressure areas but on nearly always on the east side of the low. A warm front is depicted by a red line with half-moons located on the side of the direction of its motion. Warm FrontĪ warm front is the leading edge of a relatively warmer air mass replacing a colder air mass. So, it is still called a cold front even in summer if the temperature only lowers from, for example, 95☏ (35☌) ahead of the front to near 90☏ (32☌) behind the front.Ĭold fronts nearly always extend anywhere from a south direction to a west direction from the center of low-pressure areas and never from the center of high-pressure systems. So being "ahead of the cold front" is being in the "warm" air mass and "behind of the cold front" is in the cold air mass.Īlso remember however, the terms "cold" and "warm" are relative. Phrases like "ahead of the front" and "behind of the front" refer to its motion. Cold fronts demarcate the leading edge of a cold air mass displacing a warmer air mass. Fronts Cold FrontĬold fronts are depicted by blue line with triangles pointing in the direction of motion. Finally, the pressure on either side of a front can vary significantly. Also, temperature differences can be quite noticeable from one side of a front to the other side. Winds often "converge" or come together at the fronts. But how are the boundaries between air masses depicted? We draw lines, called "fronts".įronts are usually detectable at the surface in a number of ways. In the section about the origin of Wind we have already seen the source of the "highs" and "lows". However, there are some common features typically found of these images. ![]() Weather maps come in myriads of styles with each providing different levels of information.
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