Narrative:

The preflight was normal; weather at destination was not forecast to be below 5SM +/- 1 hour of our arrival. The ceilings were not forecast to be below 2000 ft either. Thus; no alternate fuel was required/loaded. Pushback/takeoff/enroute all normal. We began descent/arrival planning approximately 50 NM prior to top of descent. Current ATIS had the field VFR. Planned for arrival utilizing visual callouts; backed up by ILS guidance. Passing through 10;000 ft; we were handed off to approach. Approach then informed us of weather below minimums for all available runways. Approach also informed us that there had been 3 aircraft go-arounds recently. This was the first notification we had received that the field was IMC. We leveled off at 8000 ft and began to weigh our options. With only 6;100 pounds of fuel onboard; we quickly determined that diverting as soon as possible was our wisest option. We informed ATC of the need to divert immediately. We ran the diversion planning feature of the computer and determined the fuel required. Estimated landing fuel was now approximately 4;000 pounds. Upon receiving ATIS we learned that the airfield was landing south. Realizing that the other aircraft had declared an emergency; we then adjusted our fuel planning assuming a terminal delay. This new fuel plan had us landing with emergency fuel also. The captain and I decided that we had to declare an emergency due to low fuel. ATC decided to turn the airport to a north flow for us and the other emergency aircraft. We landed uneventfully and blocked into the gate with 3;700 pounds of fuel. Unfortunately; this situation is very hard to avoid in the future due to weather forecasting limitations. At our time of departure; the weather was not expected to be anywhere near minimums and thus we did not bring any extra fuel. We arrived in the area prior to any ATIS updates and thus were completely taken off guard when we were informed the field was not only IFR; but that it was also below minimums. A quicker update of ATIS would have made our diversion happen sooner. Also; if center would have known that the weather was below minimums and then informed us; we would have been able to divert sooner. Another solution would have been for dispatch to inform us once the first aircraft had to go-around that the weather was worse than forecast. I believe that the weather changed too rapidly and unexpectedly for the normal weather reporting tools to be effective for inbound aircraft. I am very pleased with the crew coordination that my captain and I exercised to rapidly decide to divert. This event reaffirms my belief that any delay in deciding to divert will only exacerbate an already deteriorating situation.

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Original NASA ASRS Text

Title: A B737 flight crew encountered unexpected below-minimum weather at destination; and declared a fuel emergency to assure a successful diversion.

Narrative: The preflight was normal; weather at destination was not forecast to be below 5SM +/- 1 hour of our arrival. The ceilings were not forecast to be below 2000 FT either. Thus; no alternate fuel was required/loaded. Pushback/takeoff/enroute all normal. We began descent/arrival planning approximately 50 NM prior to top of descent. Current ATIS had the field VFR. Planned for arrival utilizing visual callouts; backed up by ILS guidance. Passing through 10;000 FT; we were handed off to Approach. Approach then informed us of weather below minimums for all available runways. Approach also informed us that there had been 3 aircraft go-arounds recently. This was the first notification we had received that the field was IMC. We leveled off at 8000 FT and began to weigh our options. With only 6;100 LBS of fuel onboard; we quickly determined that diverting as soon as possible was our wisest option. We informed ATC of the need to divert immediately. We ran the diversion planning feature of the computer and determined the fuel required. Estimated landing fuel was now approximately 4;000 LBS. Upon receiving ATIS we learned that the airfield was landing south. Realizing that the other aircraft had declared an emergency; we then adjusted our fuel planning assuming a terminal delay. This new fuel plan had us landing with emergency fuel also. The Captain and I decided that we had to declare an emergency due to low fuel. ATC decided to turn the airport to a north flow for us and the other emergency aircraft. We landed uneventfully and blocked into the gate with 3;700 LBS of fuel. Unfortunately; this situation is very hard to avoid in the future due to weather forecasting limitations. At our time of departure; the weather was not expected to be anywhere near minimums and thus we did not bring any extra fuel. We arrived in the area prior to any ATIS updates and thus were completely taken off guard when we were informed the field was not only IFR; but that it was also below minimums. A quicker update of ATIS would have made our diversion happen sooner. Also; if Center would have known that the weather was below minimums and then informed us; we would have been able to divert sooner. Another solution would have been for Dispatch to inform us once the first aircraft had to go-around that the weather was worse than forecast. I believe that the weather changed too rapidly and unexpectedly for the normal weather reporting tools to be effective for inbound aircraft. I am very pleased with the Crew coordination that my Captain and I exercised to rapidly decide to divert. This event reaffirms my belief that any delay in deciding to divert will only exacerbate an already deteriorating situation.

Data retrieved from NASA's ASRS site as of April 2012 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.