DURING VECTORS FOR A RIVER VISUAL APCH TO DCA RWY 18; WX WAS ENCOUNTERED ON THE FINAL APCH COURSE; SO APCH CTL WAS AIDING THE FLC IN VECTORS AROUND THE WX CELL. BECAUSE OF STRONG WINDS FROM THE SW; BOTH THE FLC AND CTLR HAD TO COORDINATE MANEUVERING TO REMAIN CLR OF P56; THE WHITE HOUSE.

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WE WERE APCHING THE DCA ARPT FROM THE E AND TOLD TO EXPECT RADAR VECTORS TO THE RIVER VISUAL TO RWY 18. TWO RAINSHOWERS WERE ALONG THE FINAL AT APPROX 8-10 MI FROM THE ARPT. WE ASKED FOR AND WERE TOLD TO EXPECT VECTORS INSIDE THE 8 MI DISTANCE TO AVOID THE SHOWERS. INITIALLY THE CTLR GAVE US A 250 DEG HDG. AS WE GOT CLOSER TO FINAL IT BECAME NECESSARY TO TURN FURTHER TO THE SW TO AVOID THE GROWING SHOWER. WE ASKED FOR AND RECEIVED SUCCESSIVE TURNS TOWARD THE S UNTIL WE WERE FINALLY ASSIGNED A HDG OF 190 DEGS. SHORTLY THEREAFTER; THE APCH CTLR TOLD US TO 'TURN L TO 150 DEG HDG TO INTERCEPT THE RIVER -- CLRED FOR THE RIVER VISUAL RWY 18 APCH.' IMMEDIATELY AFTER TURNING TO 150 DEGS WE PICKED UP THE WASHINGTON MONUMENT AND REALIZED WE NEED TO TURN BACK TO THE W-SW TO AVOID PROHIBITED AREA P56 AND INTERCEPT THE RIVER FINAL. WE STARTED TO TURN BACK TO THE W AND WERE ON ABOUT A 210 DEG HDG WHEN THE CTLR TOLD US TO TURN TO 210 DEGS. WE SAID WE ALREADY HAD TURNED TO 210 DEGS SO HE SAID TO TURN FURTHER R TO 240 DEG HDG AND TO KEEP IT TIGHT TO AVOID P56. WE COMPLIED -- PICKED UP THE RIVER FINAL AND LANDED WITH NO FURTHER PROBS; I DON'T BELIEVE WE VIOLATED ANY OF THE PROHIBITED AREAS; BUT MAY HAVE GOTTEN CLOSER THAN WE REALLY CARED TO. THERE WERE STRONG WINDS FROM ABOUT 240 DEGS AT 35-40 KTS THAT I THINK THE CTLR WAS HAVING A HARD TIME COMPENSATING FOR WITH THE VECTORS HE WAS GIVING US. ON OUR PART; WE PROBABLY WOULD HAVE BEEN BETTER OFF IN RETROSPECT TO WAIT FOR THE SHOWERS TO PASS OVER THE FINAL OR ASK FOR A LDA APCH. VECTORS TO A FINAL INSIDE OF 5 MI ON THE RIVER VISUAL TO RWY 18 IS POSSIBLE; BUT THERE IS LITTLE ROOM FOR DEV BECAUSE OF THE PROHIBITED AREAS.