America's critical infrastructure is facing a troubling double disruption.

The National Weather Service (NWS) has acknowledged a national radar outage affecting its radar website, following an extraordinary decision by the Federal Aviation Administration (FAA) to ground departing flights across the United States because of widespread air traffic control communications problems.

The two developments, occurring in close succession Friday afternoon, have raised serious questions about the reliability of the nation's essential transportation and weather-monitoring systems.

The NWS posted the following message on an official webpage:

"We are aware of a National Radar Outage on radar.weather.gov. We appreciate your patience as we investigate this matter. Thank you."

According to Newsforce: "Local offices have posted notices confirming the problems and saying technicians are investigating. Forecast offices continue issuing watches, warnings, and forecasts, which remain available through some external sites and official social media accounts."

The development comes as America's aviation system faces its own extraordinary emergency.

On Friday, the FAA issued a rare nationwide ground stop, ordering departing flights to remain on the ground amid serious communications problems involving air traffic control facilities across the country.

The agency cited "extraordinary circumstances" and safety concerns in ordering the unprecedented disruption to normal flight operations.