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| Base Ref 124nm Elev=0.5 deg 1 km²/pixel BOI: Boise ID 43.49N 116.2W 04/25/00 05:12 UTC Clear Mode VCP 32 Max: 62 dBZ |
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Mountain blockage
When a solid obstruction such as a mountain intercepts a radar beam, it blocks further travel of the beam beyond that point and casts a shadow within the scan. Weather or birds may be present beyond this obstruction, but they are not detected. The following reflectivity image from BOI Boise, ID shows nighttime bird migration in progress with developing storms to the far north and southeast. However, notice that no targets appear in the southwest and northeast of the station. The Owyhee Mountains to the southwest and the Boise Mountains to the northeast are blocking the radar beam from scanning the atmosphere beyond them. This pattern is typical of mountain blockage, and it appears consistently at this NEXRAD station.
| Mountain shadow around Boise ID during migration | |||||||||||||||||||||||||||||
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Because of mountain blockage, NEXRAD does not cover all of its theoretical range...
| NEXRAD coverage ranges with mountain blockage |
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