A321 Captain reported encountering moderate to severe turbulence and hail from an unseen/undetected buildup while diverting to an alternate. Left forward cockpit windshield shattered during the encounter. Aircraft landed with no other damage or injuries.

Narrative

Flight XXXX ZZZ1 to ZZZ delayed because of ground stop into ZZZ. Ground stop lifted and proceeded to ZZZ. The radar was on the entire flight. Enroute ATC advised we were to expect holding and slow to slowest practical airspeed. Holding issued and Estimated Critical Fuel given. Dispatch advised of situation and fuel via ACRS. During hold ATC was extending Estimated Critical Fuel times. I advised ATC that I was diverting to my alternate based on my bingo fuel calculations (fuel was not critical). Dispatch advised; proceeding to alternate ZZZ2. ATC issued a heading. As we proceeded; we were IMC; in and out of the clouds with haze avoiding radar returns as needed. I was pilot monitoring and was getting set up for the new destination. The visibility suddenly improved and there was a build up In front of us that was not on the radar and we could not see before hand. We had no time to react. We experienced moderate to severe turbulence. Things happened VERY VERY quickly. We heard what I thought was hail and I told the FO (First Officer) to bank right. As we banked right I heard a loud bang and the left forward windshield shattered; and I [notified ATC]. I was given a frequency change and [re-notified ATC] stating that I need to descend to 10;000 FT. We were at FL230. I was concerned that I might loose the windshield and depressurize. We were given 9;000. We proceeded to ZZZ2 and landed without incident. I taxied off the runway and safety vehicles inspected the aircraft and runway. I taxied to the gate and the Passenger deplaned. There were no reported injuries to Passengers or Crew. I communicated with Dispatch and Company safety. He stated that the Director in ZZZ3 was going to call me. We spoke briefly and he requested a picture of the windshield and any other damage that may have occurred. No observed damage noted other than the windshield and picture was sent. Crew tracking wanted the FO and I to ride in car back to ZZZ to over night. The Director arranged for us to stay the night in ZZZ2. We proceed to the hotel. The XA:30 limo was a no show. I was on hold for an extended time with the hotel/transportation desk with no response and no vehicle contact information. I hung up and talked with the duty pilot and said I would get a rideshare to ZZZ4 to finish the trip.Cause: Unobserved build up and hail while in IMC conditions. No time to react when we became visual to avoid build up.Suggestions: As a new CA (Captain) flying with a new FO we were both very consultative on the decisions we were making i.e. weather avoidance and determining bingo fuel. We discussed all things as a crew. I am not sure of how this situation could of been avoided being we were IMC. We were using the tools that we had. It was an unfortunate event with windshield damage. Thankfully no one was injured. I will continue to develop my self as a Captain and caulk this up to a learning experience.