Narrative:

Weather was deteriorating at [destination with] lightning; thunderstorms; and hail. [We] held short time [and were given] multiple vectors. Decided not to begin approach as weather was becoming significantly worse. Notified ATC of intention to divert to [alternate]. Dispatch concurred [alternate] weather suitable. [Alternate was] not on flight release as an alternate and my fuel estimate for arrival at alternate was very near my comfort level for landing. Declared emergency for minimum fuel as I was not certain of number of other flights diverting to [alternate] and possible delays there from. Approach and landing were uneventful.

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Original NASA ASRS Text

Title: B737-800 Captain elected to declare a fuel emergency and divert to an alternate when weather deteriorated at his original destination.

Narrative: Weather was deteriorating at [destination with] lightning; thunderstorms; and hail. [We] held short time [and were given] multiple vectors. Decided not to begin approach as weather was becoming significantly worse. Notified ATC of intention to divert to [alternate]. Dispatch concurred [alternate] weather suitable. [Alternate was] not on flight release as an alternate and my fuel estimate for arrival at alternate was very near my comfort level for landing. Declared emergency for minimum fuel as I was not certain of number of other flights diverting to [alternate] and possible delays there from. Approach and landing were uneventful.

Data retrieved from NASA's ASRS site as of July 2013 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.