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6/17/21 

AIM 

information. The FAA has determined that operators 
and pilots may utilize the following approved sources 
of aviation weather information: 

1.  Federal Government.

 The FAA and NWS 

collect raw weather data, analyze the observations, 
and produce forecasts. The FAA and NWS 
disseminate meteorological observations, analyses, 
and forecasts through a variety of systems. In 
addition, the Federal Government is the only 
approval authority for sources of weather observa-
tions; for example, contract towers and airport 
operators may be approved by the Feder

al 

Government to provide weather observations. 

2.  Enhanced Weather Information System 

(EWINS).

 An EWINS is an FAA authorized, 

proprietary system for tracking, evaluating, report-
ing, and forecasting the presence or lack of adverse 
weather phenomena. The FAA authorizes a certifi-
cate holder to use an EWINS to produce flight 
movement forecasts, adverse weather phenomena 
forecasts, and other meteorological advisories. For 
more detailed information regarding EWINS, see the 
Aviation Weather Services Advisory Circular 00

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and the Flight Standards Information Management 
System 8900.1. 

3. Commercial Weather Information 

Providers.

 In general, commercial providers pro-

duce proprietary weather products based on 
NWS/FAA products with formatting and layout 
modifications but no material changes to the weather 
information itself. This is also referred to as 
“repackaging.” In addition, commercial providers 
may produce analyses, forecasts, and other propri-
etary weather products that substantially alter the 
information contained in government

produced 

products. However, those proprietary weather 
products that substantially alter government

pro-

duced weather products or information, may only be 
approved for use by 14 CFR Part 121 and Part 135 
certificate holders if the commercial provider is 
EWINS qualified. 

NOTE

 

Commercial weather information providers contracted by 
FAA to provide weather observations, analyses, and 
forecasts (e.g., contract towers) are included in the Federal 
Government category of approved sources by virtue of 
maintaining required technical and quality assurance 
standards under Federal Government oversight. 

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4.  Graphical Forecasts for Aviation 

(GFA) 

a. 

The GFA website is intended to provide the 

necessary aviation weather information to give users 
a complete picture of the weather that may affect 
flight in the continental United States (CONUS). The 
website includes observational data, forecasts, and 
warnings that can be viewed from 14 hours in the past 
to 15 hours in the future, including thunderstorms, 
clouds, flight category, precipitation, icing, turbu-
lence, and wind. Hourly model data and forecasts, 
including information on clouds, flight category, 
precipitation, icing, turbulence, wind, and graphical 
output from the National Weather Service’s (NWS) 
National Digital Forecast Data (NDFD) are available. 
Wind, icing, and turbulence forecasts are available in 
3,000 ft increments from the surface up to 30,000 ft 
MSL, and in 6,000 ft increments from 30,000 ft MSL 
to 48,000 ft MSL. Turbulence forecasts are also 
broken into low (below 18,000 ft MSL) and high (at 
or above 18,000 ft MSL) graphics. A maximum icing 
graphic and maximum wind velocity graphic 
(regardless of altitude) are also available. Built with 
modern geospatial information tools, users can pan 
and zoom to focus on areas of greatest interest. Target 
users are commercial and general aviation pilots, 
operators, briefers, and dispatchers. 

b.  Weather Products. 

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The Aviation Forecasts include gridded 

displays of various weather parameters as well as 
NWS textual weather observations, forecasts, and 
warnings. Icing, turbulence, and wind gridded 
products are three

dimensional. Other gridded 

products are two

dimensional and may represent a 

“composite” of a three

dimensional weather phe-

nomenon or a surface weather variable, such as 
horizontal visibility. The following are examples of 
aviation forecasts depicted on the GFA: 

(a) 

Terminal Aerodrome Forecast (TAF) 

(b) 

Ceiling & Visibility (CIG/VIS) 

(c) 

Clouds 

(d) 

Precipitation / Weather (PCPN/WX) 

(e) 

Thunderstorm (TS) 

(f) 

Winds 

(g) 

Turbulence 

(h) 

Ice 

Meteorology 

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