24 Hour Forecasted Pressure and Front Positions in the US
|Current | 12 Hr Forecast | 24 Hr Forecast | 36 Hr Forecast | 48 Hr Forecast|
Understanding the Map Symbols
The symbols to the right are used to represent different types of weather conditions that affect the United States.
A cold front represents a boundary between cold air and warm air. The blue arrows denote the direction the cold front is moving, typically from west to east. Most cold fronts will have a noticiable change in temperature following the front's passage, although not always. Dewpoints will typically drop as well following the front's passage.
The opposite of a cold front. In this case, warmer, more humid air is overtaking colder air. The red circles face in the direction of the front's movement, which is typically from southwest to northeast.
A stationary front is a boundary between cold air and warm air that is not moving. The blue triangles point in the direction of the warmer air, while the red semicircles point in the direction of the colder air. Once the front begins to move, it will become a warm front or a cold front. There is typically heavy precipitation along the line representing a stationary front.
When a cold front overtakes a warm front, the point where the two meet becomes an occluded front. This typically occurs near a low pressure system, Normally, a low, or cyclone, has a warm front stretching east and moving north, and a cold front stretching south and moving northeast. An occluded front is represented with purple alternating semicircles and triangles pointing in the direction of movement of the front.
A trough (sometimes called a trof) is a line of low pressure in the atmosphere. While troughs can exist in both the upper atmosphere and the lower atmosphere, the troughs on this map, which are represented by dotted black lines, are in the lower atmosphere. Troughs are often associated with short waves, which can cause thunderstorms, depending on atmospheric conditions.