Narrative:

There were numerous scattered thunderstorms and twring cumulus in all quadrants of my airspace. The ASR-9, 6 channel WX was operating. However, pilots were requesting to deviate from their issued headings in areas that did not show any possible precipitation on the ATC radar. The controller workload can increase rapidly with only a moderate number of aircraft in this situation. When the pilot of the arriving B738 requested a course deviation to avoid severe WX, I assumed that he would not turn toward an area of level 5 WX that was displayed on my radar scope. I issued a clearance to maintain 3000 ft based upon that assumption. Coordination for other aircraft deviating within my airspace prevented me from noticing that the B738 was entering a restr area and came in close proximity to a VFR aircraft in that area. Since the ASR-9 can only display 2 of the 6 levels of precipitation at one time and only shows actual precipitation, it is impossible to determine which twring cumulus clouds will cause a pilot to deviate from course. I learned that controllers should establish altitude separation from restr areas and other aircraft and maintain that separation while allowing pilots to deviate around visually observed WX phenomena.

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Original NASA ASRS Text

Title: BUF CTLR ALLOWS B738 TO ENTER RESTR AIRSPACE WITH COORD INCURRING A CONFLICT WITH ANOTHER ACFT OPERATING IN THE RESTR AIRSPACE.

Narrative: THERE WERE NUMEROUS SCATTERED TSTMS AND TWRING CUMULUS IN ALL QUADRANTS OF MY AIRSPACE. THE ASR-9, 6 CHANNEL WX WAS OPERATING. HOWEVER, PLTS WERE REQUESTING TO DEVIATE FROM THEIR ISSUED HDGS IN AREAS THAT DID NOT SHOW ANY POSSIBLE PRECIP ON THE ATC RADAR. THE CTLR WORKLOAD CAN INCREASE RAPIDLY WITH ONLY A MODERATE NUMBER OF ACFT IN THIS SIT. WHEN THE PLT OF THE ARRIVING B738 REQUESTED A COURSE DEV TO AVOID SEVERE WX, I ASSUMED THAT HE WOULD NOT TURN TOWARD AN AREA OF LEVEL 5 WX THAT WAS DISPLAYED ON MY RADAR SCOPE. I ISSUED A CLRNC TO MAINTAIN 3000 FT BASED UPON THAT ASSUMPTION. COORD FOR OTHER ACFT DEVIATING WITHIN MY AIRSPACE PREVENTED ME FROM NOTICING THAT THE B738 WAS ENTERING A RESTR AREA AND CAME IN CLOSE PROX TO A VFR ACFT IN THAT AREA. SINCE THE ASR-9 CAN ONLY DISPLAY 2 OF THE 6 LEVELS OF PRECIP AT ONE TIME AND ONLY SHOWS ACTUAL PRECIP, IT IS IMPOSSIBLE TO DETERMINE WHICH TWRING CUMULUS CLOUDS WILL CAUSE A PLT TO DEVIATE FROM COURSE. I LEARNED THAT CTLRS SHOULD ESTABLISH ALT SEPARATION FROM RESTR AREAS AND OTHER ACFT AND MAINTAIN THAT SEPARATION WHILE ALLOWING PLTS TO DEVIATE AROUND VISUALLY OBSERVED WX PHENOMENA.

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.