LINES:

For this class of graphics, thin grey lines represent isobars which are defined as lines of constant pressure. In this case the pressure is at sea level. The isobars are labeled in four millibar (mb) increments and are drawn every two mb. The largest and smallest isobar values are also labeled.

COLORS:

Background color represents the amount of forecasted precipitation in 1/100 inches over the chosen time period. For example, a value of 50 (blue) would be 50/100 inches or equivalent to .5 inches of rain.

The forecast time period, forecast hour and time valid are located at the top left and center of the graphic. The color-bar located at the bottom identifies the amount of precipitation for each shading of color. Total precipitation graphics are available for 1, 3, and 24 hour periods and different regions depending on the resolution selected (36, 12 and 4 km resolutions). See below.

WHY IS THIS IMPORTANT?

Precipitation has the ability to impact a wide variety of events (daily commute, air travel, forest fires) and industries (agriculture, travel, recreation). It is important to know what type of precipitation will fall, how much precipitation will fall over a period of time and for how long. These fields help forecasters with the latter two. Combining this field with the 1000-500 mb thickness or the freezing level maps help forecasters determine the former.

UNDERSTANDING THE PLOT

Shown here is the precipitation in the past 24 hours (see top left of plot) forecasted 36 hours in the future. It is valid at 12 UTC Sat 23 July 05 (aka 05 PDT Sat 23 July 05). In other words, from July 22 2005 at 5am to July 23 2005 at 5am you can expect this much precipitation.

Along with 24-hour precipitation totals the Dept. of Atmospheric Sciences at the University of Washington also produces 3-hr and 1-hr precipitation totals. See below.