National Precipitation, Dew Point & Fronts

National Dew Point
        About this map:
Dew point is the temperature to which air must be cooled for saturation to occur. The dew point is an important measurement used to predict the formation of dew, frost, and fog. Dew point is also a good indicator of the air's actual water vapor content, unlike relative humidity, which takes the air's temperature into account.
High dew point indicates high vapor content; low dew 
point indicates low vapor content. In addition a high dew point indicates a better chance of rain and severe thunderstorms.
Use this map to determine trends in the dew point across the nation.
National Precipitation for the Last 24 Hours

        About this map:
Precipitation comes in a variety of forms and can be both beneficial and hazardous.
Use this map to view national precipitation amounts for the last 24 hour period. 
National Current Fronts

        About this map:
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity. Cold fronts may feature narrow bands of thunderstorms and severe weather, and may on occasion be preceded by squall lines or dry lines. 
Warm fronts are usually 
preceded by stratiform precipitation and fog. The weather usually clears 
quickly after a front's passage. Some fronts produce no
precipitation and little cloudiness, 
although there is invariably a wind shift. 
Cold fronts and occluded fronts generally move from west to east, while warm fronts move poleward. 
Because of the greater density of air in their wake, cold fronts and cold occlusions move faster than warm fronts and warm occlusions. Mountains and warm bodies of water can slow the movement of fronts. When a front becomes stationary, and the density contrast across the frontal boundary vanishes, the front can degenerate into a line which separates regions of differing wind velocity, known as a shearline. This is most common over the open ocean.
          Weather map symbols:
          1. cold front
          2. warm front
          3. stationary front
          4. occluded front
          5. surface trough
          6. squall/shear line
          7. dry line
          8. tropical wave         

A surface weather analysis is a special type of weather map which provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations.
Weather maps are created by plotting or tracing the values of relevant quantities such as sea-level pressure, temperature, and cloud cover onto a geographical map to help find synoptic scale features such as weather fronts.
Surface weather analyses have special symbols which show frontal systems, cloud cover, precipitation, or other important information. For example, an  H  may represent high pressure, implying fair weather. 
An   L  on the other hand may represent low pressure, which frequently accompanies precipitation. 
Various symbols are used
not  just for frontal zones and other surface boundaries on weather maps, but also to depict the present weather at various locations on the weather map.
In addition, areas of precipitation help determine the frontal type and location.
Use this map to determine the movement of current fronts across the nation.

Weather Fast Fact
Flash Flood Warning:
A flood warning issued for life/property threatening flooding that will occur within 6 hours.
It could be issued for rural or urban areas as well as for areas along the major rivers.
Very heavy rain in a short period of time can lead to flash flooding, depending on local terrain, ground cover, degree of urbanization, amount of man-made changes to the natural river banks, and initial ground or river conditions.
Dam breaks or ice jams can also create flash flooding.