Garmin GNC 420(A) Pilot's Manual & Reference page 209

Weather Products
The following weather products are available for
display on the GNC 420 unit via the Weather Data Link
interface:
• NEXRAD Data
• Graphical METAR Data
• Text-based METAR Data
• Graphical Temperature/Dewpoint Data
• Graphical Wind Data
NEXRAD Description
WSR-88D weather surveillance radar or NEXRAD
(NEXt generation RADar) is a Doppler radar system that
has greatly improved the detection of meteorological
events such as thunderstorms, tornadoes, and hurricanes.
An extensive network of NEXRAD stations provides
almost complete radar coverage of the continental United
States, Alaska, and Hawaii. The range of each NEXRAD
station is 124 nautical miles.
NEXRAD Abnormalities
There are possible abnormalities regarding displayed
NEXRAD images. Some, but not all, of those include:
• Ground clutter
• Spurious radar data
• Sun strobes, when the radar antenna points
directly at the sun
• Military aircraft deploy metallic dust (chaff) which
can cause alterations in radar scans
• Interference from buildings or mountains, which
may cause shadows
190-00140-20 Rev. K
NEXRAD Limitations
Certain limitations exist regarding the NEXRAD
radar displays. Some, but not all, are listed for the user' s
awareness:
• NEXRAD base reflectivity does not provide
• NEXRAD base reflectivity is sampled at the
• NEXRAD resolution varies, depending on the
GNC 420(A) Pilot's Guide and Reference
ADDITIONAL FEATURES
CaUTiON: NeXraD weather data is to be used
for long-range planning purposes only. Due to
inherent delays and relative age of the data
that can be experienced, NeXraD weather data
cannot be used for short-range avoidance of
weather.
sufficient information to determine cloud layers or
precipitation characteristics (hail vs. rain, etc.).
minimum antenna elevation angle. An individual
NEXRAD site cannot depict high altitude storms
at close ranges, and has no information about
storms directly over the site.
amount and complexity of the weather data being
received. The displayed NEXRAD data will reflect
the highest intensity level sampled within a 4 sq
km area (depending on available system memory).
SECTION 11
11-19