TWR LCL CTLR FORGOT THAT HE HAD AN MD80 HOLDING IN POS WHEN A B737 WAS ON FINAL FOR THE SAME RWY UNTIL THE FLC OF THE B737 INQUIRED ABOUT THE INTENTIONS OF THE HOLDING MD80.

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SIT BEGAN WHILE HOLDING SHORT OF RWY 14 AT ANC. ACR B757 LANDED AND THEN WE WERE GIVEN 'POS AND HOLD ON RWY 14' TFC; AN ACR B737; 5 MI IN TRAIL OF THE B757 AND IN SIGHT FOR US. WE EXPECTED TKOF CLRNC TO BE GIVEN AS SOON AS THE B757 CLRED THE RWY. THIS DIDN'T HAPPEN. WHEN THE B737 REACHED APPROX 2 MI OUT FOR LNDG; THE B737 ACFT APPEARED IN THE 6 O'CLOCK POS OF OUR TCASII INDICATOR. AS I REACHED FOR THE MIKE SWITCH; THE B737 CREW ASKED THE TWR ABOUT OUR STATUS; 'IS HE GOING TO TAKE OFF OR WHAT?' AFTER A FEW SECONDS OF SILENCE; THE TWR OPERATOR REQUESTED US TO HURRIEDLY CLR THE RWY. WE DID SO QUICKLY AND WHILE MANEUVERING THE ACFT INTO THE HOLD SHORT POS AGAIN; WE OBSERVED THE B737 PASS OVER THE NUMBERS FOR HIS LNDG. IN RESPONDING TO BOTH THE MD80 AND THE B737 CREW'S QUESTION ABOUT 'WHAT WAS GOING ON;' THE TWR OPERATOR STATED THAT THE 'SPACING DIDN'T WORK OUT AND THAT THE SUN'S POS IN THE SKY DIDN'T ALLOW THE TWR OPERATOR TO SEE THE MD80 WHILE ON THE RWY.' IT SEEMED LIKE THE TWR OPERATOR LOST TRACK OF US AFTER GIVING US THE 'POS AND HOLD' CLRNC. SITUATIONAL AWARENESS ON BOTH THE MD80 AND B737 CREW'S PART HELPED PREVENT EITHER A GAR OR WORSE.