Narrative:

DH8 inbound to bfl on ILS approach. There was a solid overcast layer 1000-3400 ft MSL (no breaks). When the DH8 was 14 mi final descending out of about 4000 ft, I advised the DH8 'traffic 12 O'clock position, mode C' indicates 800 ft use caution because I just had an aircraft depart L45 and climb through the clouds and come close to a previous E120 brasilia on the ILS. The DH8 said he would watch for the traffic on his TCASII. I called the traffic again when the DH8 said he was descending into IMC. Just about then the DH8 reported traffic in sight climbing through the tops of the overcast right near his right wing. The DH8 said he was turning to the left to avoid traffic. After the traffic had cleared, I reclred the DH8 to continue on the ILS. I assume the traffic had departed L45 and climb through the overcast layer. Because I had a similar situation in the same spot 20 mins prior. I knew what the base and tops were and previously asked the E120 if there were any breaks in the overcast, which he said 'no.' during this event I had a BE35 holding on the ground awaiting release for an on top clearance at L45.

Related reports:

Google
 

Original NASA ASRS Text

Title: BFL CTLR ISSUES TFC ALERT TO DSNDING DHC8 WHEN OBSERVING AN UNIDENTED ACFT CLBING IN POTENTIAL CONFLICT WITH DHC8.

Narrative: DH8 INBOUND TO BFL ON ILS APCH. THERE WAS A SOLID OVCST LAYER 1000-3400 FT MSL (NO BREAKS). WHEN THE DH8 WAS 14 MI FINAL DSNDING OUT OF ABOUT 4000 FT, I ADVISED THE DH8 'TFC 12 O'CLOCK POS, MODE C' INDICATES 800 FT USE CAUTION BECAUSE I JUST HAD AN ACFT DEPART L45 AND CLB THROUGH THE CLOUDS AND COME CLOSE TO A PREVIOUS E120 BRASILIA ON THE ILS. THE DH8 SAID HE WOULD WATCH FOR THE TFC ON HIS TCASII. I CALLED THE TFC AGAIN WHEN THE DH8 SAID HE WAS DSNDING INTO IMC. JUST ABOUT THEN THE DH8 RPTED TFC IN SIGHT CLBING THROUGH THE TOPS OF THE OVCST RIGHT NEAR HIS R WING. THE DH8 SAID HE WAS TURNING TO THE L TO AVOID TFC. AFTER THE TFC HAD CLRED, I RECLRED THE DH8 TO CONTINUE ON THE ILS. I ASSUME THE TFC HAD DEPARTED L45 AND CLB THROUGH THE OVCST LAYER. BECAUSE I HAD A SIMILAR SIT IN THE SAME SPOT 20 MINS PRIOR. I KNEW WHAT THE BASE AND TOPS WERE AND PREVIOUSLY ASKED THE E120 IF THERE WERE ANY BREAKS IN THE OVCST, WHICH HE SAID 'NO.' DURING THIS EVENT I HAD A BE35 HOLDING ON THE GND AWAITING RELEASE FOR AN ON TOP CLRNC AT L45.

Data retrieved from NASA's ASRS site as of July 2007 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.