Garmin aera 795/796 Pilot’s Guide190-01194-00 Rev. A 81Hazard Avoidance Overview GPS Navigation Flight Planning Hazard Avoidance Additional Features Appendices IndexNEXRAD data is not real-time. The lapsed time between collection, processing, anddissemination of NEXRAD images can be significant and may not reflect the currentradar synopsis. Due to the inherent delays and the relative age of the data, it shouldbe used for long-range planning purposes only. Never use NEXRAD data or any radardata to penetrate hazardous weather. Rather, use it in an early-warning capacity ofpre-departure and enroute evaluation.Composite data from all the NEXRAD radar sites in the United States is shown. Thisdata is composed of the maximum reflectivity from the individual radar sweeps. Thedisplay of the information is color-coded to indicate the weather severity level.The display of radar coverage is always active when NEXRAD is selected. Areaswhere NEXRAD radar coverage is not currently available or is not being collected areindicated in grayish-purple. Radar capability exists in these areas, but it is not activeor is off-line.neXrAD AbnorMAlItIeSThere are possible abnormalities regarding displayed NEXRAD images. Some, butnot all, of those include:• Ground clutter• Strobes and 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 radarscans• Interference from buildings or mountains, which may cause shadowsneXrAD lIMItAtIonSCertain limitations exist regarding the NEXRAD radar displays. Some, but not all, arelisted for the user’s awareness:• NEXRAD base reflectivity does not provide sufficient information to determinecloud layers or precipitation characteristics (hail vs. rain). For example, it is notpossible to distinguish between wet snow, wet hail, and rain.
