Narrative:

Our fuel load was good; dispatch operations re-filed a better weather route just before block-out. Enroute; dispatch issued a second alternate. The captain concurred. We held at a fix for 15 minutes; then were rerouted to begin an RNAV STAR. A line of storms grew quickly and solidified. We were told to expect holding but it was never issued (ATC became overwhelmed). We advised ATC we needed to deviate and it was approved. The thunderstorm line closed and a strong cell popped-up in front of us. We told ATC we needed to reverse course. We did; and held at a fix. ATC advised our destination was closed indefinitely. A second line of storms formed behind us so we were between a squall line and a frontal line. The captain and I discussed options. ATC advised us our alternated was not accepting any more diversions. A second line prevented us from determining an accurate plan and fuel for our second alternate. Another airport was available; but a second line was approaching at 50 knots so time became a serious factor. It wasn't one of our listed alternates; but was clearly the safest option. It was plan C and we couldn't accurately form plan D. Both pilots were familiar from previous operations. The captain advised operations of our diversion via ACARS. The thunderstorms became more intense than expected. A satellite phone would have allowed us to communicate with operations quickly. In this instance; we didn't have time to type into ACARS and wait for response.

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Original NASA ASRS Text

Title: B767-300 flight crew was forced to divert to an airport not filed as an alternate due to unforeseen thunderstorm buildups.

Narrative: Our fuel load was good; Dispatch Operations re-filed a better weather route just before block-out. Enroute; Dispatch issued a second alternate. The Captain concurred. We held at a fix for 15 minutes; then were rerouted to begin an RNAV STAR. A line of storms grew quickly and solidified. We were told to expect holding but it was never issued (ATC became overwhelmed). We advised ATC we needed to deviate and it was approved. The thunderstorm line closed and a strong cell popped-up in front of us. We told ATC we needed to reverse course. We did; and held at a fix. ATC advised our destination was closed indefinitely. A second line of storms formed behind us so we were between a squall line and a frontal line. The Captain and I discussed options. ATC advised us our alternated was not accepting any more diversions. A second line prevented us from determining an accurate plan and fuel for our second alternate. Another airport was available; but a second line was approaching at 50 knots so time became a serious factor. It wasn't one of our listed alternates; but was clearly the safest option. It was plan C and we couldn't accurately form plan D. Both pilots were familiar from previous operations. The Captain advised Operations of our diversion via ACARS. The thunderstorms became more intense than expected. A satellite phone would have allowed us to communicate with Operations quickly. In this instance; we didn't have time to type into ACARS and wait for response.

Data retrieved from NASA's ASRS site 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.