LTSS BETWEEN SUPP CARGO CARRIER AND CORP SMT. OPERROR.

Narrative

I WAS WORKING THE TUL APCH CTL ARR RADAR W POS COMBINED ON THE LCL CTL E POS IN THE TWR CABIN. ALL FAC CTL POSITIONS WERE BEING OPERATED BY ME FROM THE LCL CTL E (LCE) POS (GND; LCL; ARR/DEP RADAR E AND W) AS POSITIONS WERE COMBINED JUST PRIOR TO THE MID-WATCH. WX IN THE FORM OF A LINE OF SEVERE TSTMS EXTENDED FROM OFF MY SCOPE TO THE NE TO OFF SCOPE SW. TUL APCH AIRSPACE IS SFC--15000' AND UNDERLIES ZKC; ZME AND ZFW AREAS. ZFW HANDED OFF MLG X; CARGO FLT; INBOUND TO TULSA FROM THE S DSNDING TO 10000'; BUT AT FL190. THE ACFT WAS ABOUT TO ENTER THE LINE OF TSTMS WHEN INITIAL CONTACT WAS MADE I INFORMED THE PLT OF X OF THE WX DISPLAYED TO ME ON THE TWR BRITE RADAR AND ISSUED FURTHER DSCNT TO 6000'. (THE WX LINE EXTENDED ALONG THE ZFW-ZKC BOUNDARY IN THAT AREA.) ACFT X'S IMMEDIATE REPLY WAS HIS DESIRE TO CLB OUT OF THE AREA. (IT SHOULD BE NOTED THAT X RPTED SEVERE TURB WHILE I WAS CONSIDERING MY ACTIONS AND IMMEDIATELY AFTER HIS REQUEST TO CLB.) (THE ACFT NOW WAS IN THE WX AND ALMOST ON THE CENTER BOUNDARY; PERHAPS A MI S OF THE BOUNDARY.) I LOOKED ON RADAR IN FRONT OF THE ACFT BASED ON HIS NBOUND TRACK AND SAW NOTHING; SO I ISSUED A CLB AT PLT'S DISCRETION TO FL230. TUL; BY LETTER OF AGREEMENT; CLBS DEPS TO FL230 IF REQUESTING HIGHER TO ZKC'S AIRSPACE; SO I FELT I COULD AT LEAST WORK THAT OUT WITH ZKC IF NEEDED AS I SAW NO TFC FOR X. BASED ON MODE C INDICATIONS; ACFT X HAD; IN FACT; STARTED TO CLB PRIOR TO MY CLEARING HIM TO DO SO. IN ANY CASE; I DID COORDINATE WITH ZKC STILLWATER SECTOR RIGHT AFTER I ISSUED THE CLB; AND WAS TOLD NO TFC FOR X; POINTOUT APPROVED; ETC; BUT ZFW MIGHT HAVE TFC. BY THEN X WAS IN ZKC AIRSPACE CLBING OUT OF THE STORMS AND TURB. ALSO; ZFW CALLED WHILE CLB WAS BEING ISSUED TO X TO ASK WHY HE WAS CLBING; AN INDICATION HE HAD ALREADY STARTED BEFORE BEING CLRED. IT APPEARED ZFW HAD SMT ACFT Y AT FL200; 4.6 MI NE OF ACFT X; SWBND IN ZKC AIRSPACE AND JUST ON THE NORTHERN EDGE OF THE WX. HIS TARGET AND DATA BLOCK WERE NOT VISIBLE TO ME DUE TO THE BRIGHT BLOOMING OF WX RETURN ON TWR BRITE RADAR. ON THE APCH CTL DISPLAY IN THE TRACON; THIS TARGET WOULD HAVE BEEN VISIBLE TO ME. THE 2 ACFT PASSED .9 MI/400' VERT FROM EACH OTHER. MY DECISION WAS A SPLIT SECOND ONE BASED ON WHAT I COULD SEE AND WHAT INFO I HAD; BUT I STILL FEEL THE ODDS WERE GREATER FOR STRUCTURAL FAILURE THAN FOR A MIDAIR COLLISION AND I DID WHAT I FELT WAS RIGHT UNDER THE CIRCUMSTANCES.