DURING FINAL APCH; ACFT ENCOUNTERS HVY RAIN AND HAIL. WINDSHEAR WARNING SOUNDED BY ACFT GPWS SYS. FLC INITIATES GAR.

Narrative

THE ACFT EXPERIENCED AN UNANTICIPATED HAIL ENCOUNTER ON APCH TO RWY 19R AT IAD. WHILE IN THE DSCNT TO IAD; SEVERAL SMALL CELLS WERE OBSERVED ON RADAR IN THE WASHINGTON AREA. ONE CELL; DISPLAYED IN RED; ABOUT 2 BY 3 MI ACROSS WAS OBSERVED NEAR THE RINKS LOM. BOTH PLTS ESTIMATED THE TOPS OF THE CELLS TO BE ABOUT 10000 FT OR LESS. ABOUT 10 MI FROM RINKS THE CAPT; WHO WAS THE PNF; ASKED APCH ABOUT CONDITIONS ON FINAL APCH. THE CTLR RESPONDED THAT THERE WERE 'NO COMPLAINTS.' BASED ON THIS REPORT AND BY OBSERVING THAT OTHER CELLS IN THE AREA HAD BASES GENERALLY ABOVE 2000 FT; BOTH PLTS AGREED THAT IT WAS LIKELY THAT VMC WOULD BE MAINTAINED FOR MOST OF THE APCH. AT 5 MI FROM THE LOM; THE CAPT AGAIN INQUIRED ABOUT CONDITIONS ON FINAL. THE RESPONSE AGAIN WAS 'NO COMPLAINTS.' DURING THIS TIME; THE CREW OBSERVED 3-4 ACFT ON TCASII TRANSIT FINAL APCH TO LNDG. APPROACHING RINKS; IT WAS NOTED ON RADAR THAT THE CELL HAD MOVED E AND WAS MOSTLY CLR OF THE FINAL APCH COURSE. AT ABOUT THIS TIME; APCH ASKED THE ACFT AHEAD OF US ABOUT CONDITIONS ON FINAL. HE RESPONDED THAT ACFT 'WOULD LOSE SIGHT OF THE RWY.' WE COULD SEE NOW THAT WE WOULD ENTER IMC ON THE APCH. SHORTLY AFTER PASSING RINKS; THE ACFT ENTERED RAIN; FOLLOWED VERY SHORTLY BY WHAT SEEMED TO BE SMALL HAIL. THE HAIL LASTED FOR 5-10 SECONDS. IT WAS FOLLOWED BY HVY RAIN. AT THIS TIME; THE AUTOPLT DISCONNECTED AND THE FLT DIRECTOR DISAPPEARED FROM VIEW. DUE TO THE RAPIDLY DETERIORATING CONDITIONS; THE CAPT INSTRUCTED THE FO TO INITIATE A GAR. AS THE GAR WAS INITIATED; A SINGLE WINDSHEAR WARNING SOUNDED. THE ACFT QUICKLY RETURNED TO VMC AND STABLE FLT CONDITIONS. AN UNEVENTFUL APCH AND LNDG WAS MADE. AT THE GATE; AN ENTRY REGARDING HAIL ENCOUNTER WAS MADE IN THE LOGBOOK. THE CREW OBSERVED NO NOTICEABLE DAMAGE.