Jesus on big signs

John 4:48 Then Jesus said to him, “Unless you see signs and wonders you (plural) will not believe.”

Mk 8:11-12 The pharisees came and began to argue with him, asking him for a sign from heaven, to test him. And he sighed deeply in his spirit and said, “Why does this generation ask for sign? Truly I tell you, no sign will be given to this generation.”
Mark has this happening immediately after Jesus has fed the 4000.
The sigh deeply in his spirit is interesting- a sadness there at the patheticness of the generation? a sigh that people won't read the signs that are there? That they won't seek out what is most important in life? That they wont follow clues like hope, life and love and see where they go? That they have a history unlike any other peoples- this interaction with the God of the Universe- the covenants- the substantial revelation of his character- yet they do not hear or see, they do not understand and they do not turn and seek forgiveness- from the Father- which is the very thing he wants to do- that is his nature- Is there anyone among you who, if your child, asks for bread, will give a stone? Or if the child asks for a fish, will give a snake? If you then, who are evil, know how to give good gifts to your children how much more will your Father in heaven give good things to those who ask him!

The pharisees and Sadducees came, and to test Jesus they asked him to show them a sign from heaven. He answered them, “When it is evening, you say, 'It will be fair weather, for the sky is red.' And in the morning, 'It will be stormy today, for the sky is red and threatening.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times. An evil and adulterous generation asks for a sign, but no signs will be given to it except the sign of Jonah.”
(Mt 16: 1-4)