Date: 201511
Local time of day: 1801-2400
Location: SAT.TRACON, TX
Flight conditions: IMC
Weather elements / visibility: Thunderstorm; Turbulence; 10
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E SAT
ATC / advisory: TRACON SAT
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Other / Unknown; Situational Awareness
Second reporter function: First Officer
Anomaly: Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: General Physical Injury / Incapacitation
Contributing factors: Weather
Primary problem: Weather

Narrative: Enroute to SAT during descent; we encountered turbulence bordering on severe. The only turbulence forecast for route of flight was for the [departure] area. As part of preflight briefing; I instructed the flight attendants that while previous pilots had informed us there was a smooth ride into [departure airport]; they should remain seated until I gave them a call. I also used [weather forecast] to brief the FO on weather along our route of flight. [Weather forecast] displayed the briefed turbulence over [departure airport]; some significant weather well east of our route of flight and a possible (very thin line) of rain showers around Abilene.We let the flight attendants up at FL 330. Enroute to SAT north of Abilene; I switched the radar on (we could see the storms off to the east (75 miles). During the descent passing FL 290; I observed ground obscuration of indeterminate height and we asked ATC about the rides in the descent. We were told there were no adverse reports. Believing the obscuration to be associated with the low ceiling I told the flight attendants we were concerned about the lower clouds and that we were at FL270 and 109 miles from the airport and that they should clean the cabin and sit down and we would ding them again at 10;000 feet for the 10;000 feet announcement. Passing 250 we began to encounter clouds and light turbulence; so I called the flight attendants again; apologized told them they better take their seats and we would try to find time to clean the cabin on the other side of the clouds. The FA A announced 'flight attendants take your seats'.We leveled at 240; for a short period the ride smoothed out then we were cleared to STONEWALL ONE at 10;000 feet. At this time descent speed was set for 280 and I was maintaining approximately 270 knots. We were also still using the radar adjusting angle for elevation with radar now set to the 80 mile scale. Passing FL190 we observed more clouds along our route of flight and now small cells started to pop up on our radar with several 10 miles left and one cell four miles right of our route of flight. We asked ATC for a deviation left of course of five degrees; radar scale was now reduced to 20-40 miles with angle between minus .5 to plus1; passing 17;000 feet a very small cell (1/4 mile in diameter) popped up on radar directly in front of our route of flight and 1/2 mile ahead. Entering the clouds we encountered a couple of bumps of light turbulence followed a few seconds later by moderate and occasional turbulence bordering on severe lasting five to eight seconds.We exited the cloud and I called to ask the flight attendants if everything was okay. The B and C informed me that they were not okay and that the C had hit her head and they were assessing the situation. We informed ATC of the turbulence waited two minutes then asked the flight attendants about their condition. They informed us they were okay (with the head bump) we asked if there were any issues/injuries in the cabin and were again informed no. We asked if they wanted to have the paramedics meet them (the flight attendants) and were informed no. We spoke with the flight attendants one more time during the descent prior to 10;000 feet. Subsequently; the flight attendants notified us that they would like the paramedics to meet them at the aircraft. The paramedics evaluated the B and C flight attendants and determined that an immediate hospital visit was not required. The C reported that she had hit her head and the B stated she had injured her back when she fell out of her seat. At the hotel; I provided both flight attendants with my contact information and asked them to let me know if they required additional medical assistance.


Second narrative: [Report narrative contained no additional information.]


Synopsis: While descending into SAT; the B737 crew reported occasional turbulence bordering on severe which resulted in two flight attendants with undetermined injuries. The flight attendants had been told to take their seats; and apparently were seated but were not completely strapped in.