Weather Maps and Symbols. On any given day, there's plenty of activity on a weather map. Frontal boundaries and the "Highs" and "Lows" are the prominent features on an average weather map you might see on the TV news. Let's take a closer look at what they mean.

Cold Front. A blue line with points indicating the direction of movement. Generally cold fronts move west to east across the USA. Cold fronts represent the boundary between cold and warm air masses, with the colder air behind the front. Quite often an advancing cold front triggers rain or severe weather, especially across the Midwest.
Warm Front. A red line with bumps indicating the direction of movement. Warm fronts represent a boundary between warm and cold air masses, with the warmer air behind the front. They generally move from west to east and sometimes move in advance of low pressure areas. They usually bring a change from cold to mild temperatures.
Stationary Front. A red and blue line with alternating points and bumps indicates a frontal boundary that is not moving, or moving very slowly. The winds on either side of a stationary front blow in opposite directions, but in a parallel fashion. The differing air masses have very little interaction.
Occluded Front. A purple line with points and bumps indicates a situation where a cold front has overtaken a warm front, or vice versa. Occluded fronts are complex weather systems and can often occur near the centers of low pressure areas. Weather near an occluded front is mixed and changeable. If a cold air mass overtakes a warm one, it's called a "cold occlusion". If a warmer air mass overtakes a colder one, it's called a "warm occlusion".

This is a typical surface station model report from a National Weather Service station. There is a large amount of information displayed including temperature, dew point, barometric pressure (in millibars) and trend. Also shown is sky cover (%) wind speed and direction (from). Each station is represented on the daily weather map in this fashion.

This is a legend of commonly-used weather symbols. You will find these symbols on maps featuring "surface plots". You usually won't find TV weather maps showing these types of symbols, because they are not very well known to the general public.

Centers of "high" and "low" pressure are indicated by either an H for "High" or an L for "Low". You will often see several fronts trailing low pressure centers. Air flows clockwise around and outward from centers of high pressure, and counterclockwise and inward the centers of low pressure.

Here is a typical weather map with satellite and radar overlays.

There are High Pressure centers over Colorado, Washington and Alabama. A Stationary Front extends across the Mid-Atlantic States and into the Midwest. There's a Low Pressure center over Minnesota and another moving onto the California coast. Cold Fronts are moving across Texas, Kansas and Missouri. Look closely and you'll see a small Occluded Front near the Minnesota Low.

Green shading indicates areas where precipitation is falling. The white areas are clouds. The thin blue lines connect points of equal barometric pressure. They are called Isobars, and help meteorologists identify air masses.

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