Narrative:

During cruise flight en route to ZZZ; we were advised to plan a reroute or a hold at zzzzz intersection. We asked dispatch to run numbers and I began working on fuel planning numbers on our end. The reroute was fairly significant; adding about 200 miles to our route. The FMS was unable to calculate the reroute in the 'what if' functionality. I added up the mileage and my gut said it was going to be really close and that time was definitely of the essence if we were going to be able to accept it. We of course waited for dispatch's response; which came back after some delay. We had already entered the hold and calculated bingo from zzzzz. As I suspected; the minimum fuel required was only about 300 pounds less than our current fob. I advised ATC that we could accept the reroute only if we were given an immediate and direct turn. ATC complied with my request and we continued to ZZZ via an arrival. We immediately declared minimum fuel. With the modification to the flight plan; I was better able to use the FMS to further aid in fuel monitoring. We were now projecting to land with about 2600 pounds. I then modified our performance initialization (switched to lrc and steeper descent) to conserve as much fuel as possible for the remainder of cruise. We also received a couple shortcuts; which helped us out a little as well.unfortunately; when we arrived with ZZZ approach; there were storms approaching over the river. The winds at the field were shifting significantly and we were given two runway changes before they ultimately closed the field and attempted to put us into a hold over ZZZZZ1 intersection. With already being at minimum fuel; it was not possible to wait for ZZZ to open back up. We then changed our destination to ZZZ1 and initiated the diversion. ATC then began vectoring us northeast into the edges of the storms. We attempted to negotiate and tell them we were unable to comply with vectors through the weather; but [we] were told by approach that they had only three options: opposite direction with inbound heavy; skirting the edge of the weather; or turning around into the weather to go back the way we came. Skirting the weather seemed the safest choice given the combination of factors. We experienced moderate turbulence due to the weather and speed and altitude variations greater than 100 feet and 10 knots; but aircraft control was well maintained by the first officer. I then attempted to ascertain ATC's plan for our approach in order to determine if we were going to be in a fuel emergency situation. Their plan was for extended 15 NM+ vectors out to land on the [runway] xxs in ZZZ1. We exited the weather; obtained performance; notified dispatch; and performed all checklists and then transferred controls to me prior to landing successfully on runway xxl in ZZZ1. The fuel on landing was about 1800 pounds.to the best of my knowledge; no procedures or regulations were violated. However; altitude and speed deviations occurred and were managed to the best of our ability during the forced vectors through storms. I wish I had more information during the decision to reroute. The forecast didn't call for an alternate and we didn't have fuel to add one in-flight. Though I suspected the reroute was due to severe weather avoidance plan in the area; when I queried ATC they were too busy to acknowledge and explain the holding and reroute. Live ground based radar and weather available in-flight would have been a real asset and would have likely resulted in an earlier and safer diversion decision.

Related reports:

Google
 

Original NASA ASRS Text

Title: EMB-175 flight crew reported that due to weather; they landed at an alternate airport with less that minimum fuel on board.

Narrative: During cruise flight en route to ZZZ; we were advised to plan a reroute or a hold at ZZZZZ intersection. We asked Dispatch to run numbers and I began working on fuel planning numbers on our end. The reroute was fairly significant; adding about 200 miles to our route. The FMS was unable to calculate the reroute in the 'What If' functionality. I added up the mileage and my gut said it was going to be really close and that time was definitely of the essence if we were going to be able to accept it. We of course waited for Dispatch's response; which came back after some delay. We had already entered the hold and calculated Bingo from ZZZZZ. As I suspected; the minimum fuel required was only about 300 pounds less than our current FOB. I advised ATC that we could accept the reroute only if we were given an immediate and direct turn. ATC complied with my request and we continued to ZZZ via an arrival. We immediately declared minimum fuel. With the modification to the flight plan; I was better able to use the FMS to further aid in fuel monitoring. We were now projecting to land with about 2600 pounds. I then modified our performance initialization (switched to LRC and steeper descent) to conserve as much fuel as possible for the remainder of cruise. We also received a couple shortcuts; which helped us out a little as well.Unfortunately; when we arrived with ZZZ Approach; there were storms approaching over the river. The winds at the field were shifting significantly and we were given two runway changes before they ultimately closed the field and attempted to put us into a hold over ZZZZZ1 intersection. With already being at minimum fuel; it was not possible to wait for ZZZ to open back up. We then changed our destination to ZZZ1 and initiated the diversion. ATC then began vectoring us northeast into the edges of the storms. We attempted to negotiate and tell them we were unable to comply with vectors through the weather; but [we] were told by Approach that they had only three options: opposite direction with inbound heavy; skirting the edge of the weather; or turning around into the weather to go back the way we came. Skirting the weather seemed the safest choice given the combination of factors. We experienced moderate turbulence due to the weather and speed and altitude variations greater than 100 feet and 10 knots; but aircraft control was well maintained by the First Officer. I then attempted to ascertain ATC's plan for our approach in order to determine if we were going to be in a fuel emergency situation. Their plan was for extended 15 NM+ vectors out to land on the [Runway] XXs in ZZZ1. We exited the weather; obtained performance; notified Dispatch; and performed all checklists and then transferred controls to me prior to landing successfully on Runway XXL in ZZZ1. The fuel on landing was about 1800 pounds.To the best of my knowledge; no procedures or regulations were violated. However; altitude and speed deviations occurred and were managed to the best of our ability during the forced vectors through storms. I wish I had more information during the decision to reroute. The forecast didn't call for an alternate and we didn't have fuel to add one in-flight. Though I suspected the reroute was due to severe weather avoidance plan in the area; when I queried ATC they were too busy to acknowledge and explain the holding and reroute. Live ground based radar and weather available in-flight would have been a real asset and would have likely resulted in an earlier and safer diversion decision.

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.