NEXRAD stations

I am cheerfully watching the NEXRAD data flow in here, it is great to see!

However, I am seeing some products from stations that are not in my WXP
rad.cty list of stations:

FFG
GID
LMK
TOP
UNR

TOP is easy to guess, it is TWX (Topeka). Can anyone shed light on the
rest of these?


Also, in clear air mode, how can you have a negative reflectivity? Is a
negative return ever really due to precipitation?

Thanks,
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