Narrative:

We were enroute. We had flown earlier that day and knew there was some turbulence in the area. Looking at the weather packet; we only noted an area of moderate along our route from FL340 to FL390. The captain asked the flight attendants to remain seated until he called them enroute. During the climb out; we did experience some light turbulence; and asked ATC about the rides. They said that fl 390 and above had been reported as 'good ride.'we leveled off at FL390 and did have a 'good ride' (only small areas of light chop.) the captain told the flight attendants they could start their service. The flight continued to be mostly smooth so the captain turned the seatbelt sign off. From that point on; we did not received any adverse ride reports. We had the radar on for most of the flight and were showing no weather ahead. We were given an initial decent to FL350 with a crossing restriction of 11;000 feet at kayla. The captain turned the seatbelt sign on for the descent. We never leveled off at FL350 because we were already high for a crossing restriction. We were asked to keep the speed up. With the huge tailwind; I transitioned 310 knots to maintain the flight path. The descent was not turbulent and we had not heard any other aircraft reporting adverse rides. At approximately FL210; we encountered moderate turbulence and the airspeed quickly jumped up 20 knots and showing trend into vmo. I pulled back on the yolk to stop the descent; the autothrottles were already at idle. The captain asked flight attendants to take their seats over the PA. The airspeed responded just under 340 knots. It seemed we were in the clear and it had been small sheer zone. We then encountered severe turbulence at approximately fl 200. The airspeed instantly increased from around 310 to 340-350. I immediately pulled back on yolk to slow plane down and thrust lever were still at idle. The airspeed was slow to respond. I eventually got it slowed to 280 and we continued descent. The plane was continuously jolted and banked abruptly. The whole encounter lasted about three to four minutes. At approximately fl 180 we were clear of the severe turbulence. The flight attendant called the captain and told him the aft flight attendant injured her ankle trying to get to her seat. The captain reported the severe turbulence to ATC and dispatch. We were given relief on the crossing restriction. The rest of the flight was uneventful. The paramedics met us at gate and attended to the injured flight attendant. There were no other injuries report to us.

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Original NASA ASRS Text

Title: An Air Carrier crew descending into a Mid Continent airport encountered un-forecast severe turbulence which resulted in a Flight Attendant injury before the attendants had an opportunity to be seated.

Narrative: We were enroute. We had flown earlier that day and knew there was some turbulence in the area. Looking at the weather packet; we only noted an area of Moderate along our route from FL340 to FL390. The Captain asked the Flight Attendants to remain seated until he called them enroute. During the climb out; we did experience some Light Turbulence; and asked ATC about the rides. They said that FL 390 and above had been reported as 'good ride.'We leveled off at FL390 and did have a 'good ride' (only small areas of light chop.) The Captain told the Flight Attendants they could start their service. The flight continued to be mostly smooth so the Captain turned the seatbelt sign off. From that point on; we did not received any adverse ride reports. We had the radar on for most of the flight and were showing no weather ahead. We were given an initial decent to FL350 with a crossing restriction of 11;000 feet at KAYLA. The Captain turned the seatbelt sign ON for the descent. We never leveled off at FL350 because we were already high for a crossing restriction. We were asked to keep the speed up. With the huge tailwind; I transitioned 310 knots to maintain the flight path. The descent was not turbulent and we had not heard any other aircraft reporting adverse rides. At approximately FL210; we encountered Moderate Turbulence and the airspeed quickly jumped up 20 knots and showing trend into Vmo. I pulled back on the yolk to stop the descent; the autothrottles were already at idle. The Captain asked Flight Attendants to take their seats over the PA. The airspeed responded just under 340 knots. It seemed we were in the clear and it had been small sheer zone. We then encountered Severe Turbulence at approximately FL 200. The airspeed instantly increased from around 310 to 340-350. I immediately pulled back on yolk to slow plane down and thrust lever were still at idle. The airspeed was slow to respond. I eventually got it slowed to 280 and we continued descent. The plane was continuously jolted and banked abruptly. The whole encounter lasted about three to four minutes. At approximately FL 180 we were clear of the severe turbulence. The Flight Attendant called the Captain and told him the aft Flight Attendant injured her ankle trying to get to her seat. The Captain reported the Severe Turbulence to ATC and Dispatch. We were given relief on the crossing restriction. The rest of the flight was uneventful. The paramedics met us at gate and attended to the injured Flight Attendant. There were no other injuries report to us.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.