We present high-resolution echelle observations of SN 2011dh , which exploded in the nearby , nearly face-on spiral galaxy M51 .
Our data , acquired on three nights when the supernova was near maximum brightness , reveal multiple absorption components in Na i D and Ca ii H and K , which we identify with gaseous material in the Galactic disk or low halo and in the disk and halo of M51 .
The M51 components span a velocity range of over 140 km s ^ { -1 } , extending well beyond the range exhibited by H i 21 cm emission at the position of the supernova .
Since none of the prominent Na i or Ca ii components appear to coincide with the peak in H i emission , the supernova may lie just in front of the bulk of the H i disk .
The Na i /Ca ii ratios for the components with the most extreme positive and negative velocities relative to the disk are \sim 1.0 , similar to those for more quiescent components , suggesting that the absorption originates in relatively cool gas .
Production scenarios involving a galactic fountain and/or tidal interactions between M51 and its companion would be consistent with these results .
The overall weakness of Na i D absorption in the direction of SN 2011dh confirms a low foreground and host galaxy extinction for the supernova .