"Loss of radar contact due to radar clutter (weather)" just at the time when we needed ATC more than ever and options were few if any
In Vietnam War Years....using Army operated GCA sites for "Radar Navigation and Approaches"....during Monsoon Season the dreaded words..."Radar Contact lost...Resume own navigation!" were a certainty upon being in solid cloud...much less Monsoon Rains.
I always wondered what method they thought we would use upon being told that as there might generally was not an operable Nav Receiver aboard any of the Helicopters.....assuming the NDB's might be working....which they usually were not.