Why is it that overcast days will delay a flight? Can't they use the same technology they use at night?

Question

to see the incoming air traffic? Morning overcast are notorius for the domino effect delays at SFO

Answer 1

Overcast by itself will not cause a delay.  At SFO, the problem is fog.  Fog, which is essentially a cloud resting on the ground, can reduce visibility to almost zero, and there is NO technology that will allow a landing in such conditions for most flights.

Fog is a frequent problem at many airports in addition to SFO, and can occur at almost any airport.

Cloudy conditions are often associated with other kinds of bad weather:  thunderstorms, wind shear, ice, tornadoes, and other things that will require flights to be delayed or diverted.

Night flight is often in the best of conditions.  There is nothing more beautiful than flying across inhabited lands, forests, deserts, lakes, and seas at night in good visibility.

Answer 2

Because the rules for ATC seperation change when the visibility changes. A greater spacing is required so it takes longer to get the same amount of departures out.

Answer 3

if you mean the fog at SFO...visibility on the ground is way, way better at night

even with state of the art radar, you still want someone watching what's happening on the ground.