Surface Help Page
Dewpoint is a measure of air moisture content. By contouring them, a forecaster can see regions of moist or dry air. You can see moisture ridges (higher values of moisture extending northward, surrounded by lower values to it's east and west), drylines, fronts, and many other features.
Forecasting temperature is also very dependent upon dewpoints. The more moist the air is, the less the temperature fluctuation. In winter, a 5 degree dewpoint could lead to a very cold night as the air is very dry. A forecast for fog must involve a decision on how close the low temperature will be to the dewpoint. The amount of moisture advection must also be taken into account.
Current weather symbols such as fog, rain, snow, showers, etc... are plotted on this map as well. Every forecaster should start by looking at weather observations. You cannot forecast if you do not know what is currently happening. By locating fronts and seeing the weather associated with it, a forecaster may have a better idea of what to expect in the future. For example, thunderstorms along a front in the morning may mean that the cap is weak and thunderstorms may not be as strong beacuse they are happening so early. (Wx symbols image provided by the University of Illinois.)
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| Surface Plots | Weather Symbols and Dewpoints | 3 Hour Pressure Falls |