TRACON controller assigned an altitude below the MVA when vectoring to clear weather; the aircraft n...

Narrative:

I told aircraft X to expect ILS runway 28R and descended the aircraft to FL50. I was expecting the aircraft to join the arrival and continue to the downwind. To his north/northwest; was a large moderate area of precipitation. It appeared that it would be better to turn the aircraft towards the north and take him on the east side of the weather which would provide less exposure to the growing weather in the area and provide an easy entry towards the final approach course. In doing so; I failed to amend the aircraft's assigned altitude that would be compatible with the MVA's that the aircraft would traverse on his new route. I noticed that the aircraft was descending below the MVA and issued an altitude compatible with the terrain and MVA; but not before the aircraft descended below the MVA. Honestly; I really don't know why I assigned him FL50; and even in the playback you can see I thought he was descending to 70. If I were to have kept the aircraft on the original route; there wouldn't have been any issue with the MVA. This happened in the last hour of my workweek to which I was fatigued. In the future; I would take extra steps to check altitude assigned and any clearances especially when I'm feeling fatigued.

Original NASA ASRS Text

Title: TRACON Controller assigned an altitude below the MVA when vectoring to clear weather; the aircraft never actually descending below authorized altitudes.

Narrative: I told Aircraft X to expect ILS Runway 28R and descended the aircraft to FL50. I was expecting the aircraft to join the arrival and continue to the downwind. To his north/northwest; was a large moderate area of precipitation. It appeared that it would be better to turn the aircraft towards the north and take him on the east side of the weather which would provide less exposure to the growing weather in the area and provide an easy entry towards the final approach course. In doing so; I failed to amend the aircraft's assigned altitude that would be compatible with the MVA's that the aircraft would traverse on his new route. I noticed that the aircraft was descending below the MVA and issued an altitude compatible with the terrain and MVA; but not before the aircraft descended below the MVA. Honestly; I really don't know why I assigned him FL50; and even in the playback you can see I thought he was descending to 70. If I were to have kept the aircraft on the original route; there wouldn't have been any issue with the MVA. This happened in the last hour of my workweek to which I was fatigued. In the future; I would take extra steps to check altitude assigned and any clearances especially when I'm feeling fatigued.

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.

Attributes
ACN	1088052
Time
Date	201305
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

TRACON controller assigned an altitude below the MVA when vectoring to clear weather; the aircraft never actually descending below authorized altitudes.