What does a clear radar display mean regarding weather?

7-1-11. Weather Radar Services
a. The National Weather Service operates a network of radar sites for detecting coverage, intensity, and
movement of precipitation. The network is supplemented by FAA and DoD radar sites in the western sections
of the country. Local warning radar sites augment the network by operating on an as needed basis to support
warning and forecast programs.
b. Scheduled radar observations are taken hourly and transmitted in alpha-numeric format on weather
telecommunications circuits for flight planning purposes. Under certain conditions, special radar reports are
issued in addition to the hourly transmittals. Data contained in the reports are also collected by the National
Center for Environmental Prediction and used to prepare national radar summary charts for dissemination on
facsimile circuits.
c. A clear radar display (no echoes) does not mean that there is no significant weather within the coverage of
the radar site. Clouds and fog are not detected by the radar. However, when echoes are present, turbulence can
be implied by the intensity of the precipitation, and icing is implied by the presence of the precipitation at
temperatures at or below zero degrees Celsius. Used in conjunction with other weather products, radar provides
invaluable information for weather avoidance and flight planning.
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FIG 7-1-10
NEXRAD Coverage
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FIG 7-1-11
NEXRAD Coverage
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FIG 7-1-12
NEXRAD Coverage
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d. All En Route Flight Advisory Service facilities and FSSs have equipment to directly access the radar
displays from the individual weather radar sites. Specialists at these locations are trained to interpret the display
for pilot briefing and inflight advisory services. The Center Weather Service Units located in ARTCCs also have
access to weather radar displays and provide support to all air traffic facilities within their center's area.
e. For more detailed information on PIREPS, users can refer to the current version of the Aviation Weather
Handbook, FAA-H-8083-28.
REFERENCE-
Pilot/Controller Glossary Term- Precipitation Radar Weather Descriptions.
AIM, Para 7-1-26, Thunderstorms.
Chart Supplement, Charts, NWS Upper Air Observing Stations and Weather Network for the location of specific radar sites.