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Prog chart basics

Updated: Feb 23, 2022

If you use the EZWxBrief progressive web app EZImagery, you likely have run across the Prog Charts collection. There are some high level details in the EZWxBrief Pilots Guide, but it's important to expand a bit more on this widely used weather guidance.

First, there is a similar set of prog charts that you may find on the Aviation Weather Center (AWC) website available here. However, the source of the prog charts used in EZWxBrief are those created by the Weather Prediction Center (WPC). Although the AWC site prog charts have a similar look and feel, the discussion to follow is strictly directed toward the forecasts found on the WPC website and should NOT be carried over to the AWC progs.

These prog charts come in a short and extended range variety. This discussion will focus on the short range progs which are those with a forecast lead time of 6 to 60 hours. These short range forecasts are issued twice a day and include the expected surface pressure patterns (isobars), circulation centers (highs and lows) and fronts. You may also see surface troughs, drylines and squall lines depicted as well. This forecast extends over most of North America and is produced by highly trained meteorologists at the Weather Prediction Center in College Park, Maryland.

A color mosaic depicting the type, coverage (extent) and likelihood of precipitation are extracted from the National Digital Forecast Database (NDFD) that is prepared by forecasters at the NWS local Weather Forecast Offices (WFOs) in collaboration with the WPC. The county warning areas (CWAs) for the WFOs are shown below. Consequently, the precipitation forecast depicted on these prog charts is strictly limited to the conterminous U.S. and coastal waters and does not extend into Canada or Mexico.