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We have discovered a candidate young magnified supernova (SN) in a galaxy at redshift z=1.76 that is strongly lensed by the foreground RX J1347-1145 (z=0.451) galaxy cluster. Two lens models predict magnifications of 4--4.5 for the observed image of the transient. An ongoing SNAP program acquired imaging of the field on May 18th comma and do not detect the SN candidate. From imaging acquired on the program.s last visit to the field on May 30th comma we detect a source with F110W = 25.8+-0.3 mag comma with no detection in F606W. Consequently comma the first detection is when the SN is younger than 4 days in the rest frame at z=1.76. If the SN is a Type Ia SN comma it can be used to provide a novel test of galaxy cluster models. prediction at high magnification. If a core-collapse SN comma its addition would improve constraints on the core-collapse SN rate at z=1--2 from cluster-magnified supernovae (SNe) comma which are in tension with that inferred from blank fields. Finally comma the SN may reappear in virgul9.5 years in an arc of the same galaxy at much greater magnification comma where it would be detected by LSST comma and would provide an extremely precise time delay comma constraints on the value of H0 comma and test of lens models. We propose to measure the light curve of the magnified SN comma which should reach a peak in very early July if it is a Type Ia SN comma and acquire a near-infrared G102 grism spectrum to determine its spectroscopic type.