Date: 201210
Local time of day: 0601-1200
Location: SLVR.Airport, FO
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
ATC / advisory: TRACON SLVR
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction; Situational Awareness; Human-Machine Interface
Second reporter function: Captain; Pilot Flying
Anomaly: ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Airport; Procedure
Primary problem: Procedure

Narrative: While approaching SLVR from the southwest; deviating for weather; we maneuvered to the 240 degree radial off the VIR VOR. The Controller queried our position and then cleared us to descend to 7;000 MSL. As we began our descent we were both monitoring terrain and weather while the Relief Pilot was reviewing the SLVR area charts for MSA altitudes. The Captain verbalized the MSA of 8;000 FT as depicted on the approach chart. We advised the Controller we would continue deviating south of the 240 degree radial so as to remain clear of weather. Before 35 DME the Controller recleared us to 6;000 (below the adjacent airway safe altitude) and then approaching 30 DME the Controller re-cleared us to 5;000 (below the adjacent airway safe altitude). The Captain noted his terrain display showing 5;100 and green and verbalized he was only descending to 6;000 to ensure we remained clear of terrain. I advised Controller who only responded 'continue descent to 5;000 FT;' which we assumed was for crossing traffic. The Captain had partial speedbrakes deployed while descending and maneuvering to remain clear of weather; in VMC and maintaining visual contact with the terrain while complying with the Controller's clearance. At this point we got an EGPWS 'Terrain' alert. We remained VMC and clear of all terrain and had situational awareness. Upon receiving the alert the Captain instinctively retracted the speed brakes while decreasing his descent rate. We maintained 6;000 FT until crossing the last of the terrain southwest of SLVR and the proceeded direct to the VIR VOR for the approach. We assumed that the alert was generated due to the predictive nature of the system combined with the local area terrain; descent rate and speed brakes being deployed. This report was submitted to highlight the Controller's inappropriate clearances to descend to an unsafe altitude given the proximity of the surrounding terrain. This sequence is fatiguing under the best of conditions while this particular day was extraordinarily so due to our late departure.


Second narrative: [No substantive additional information was provided by the secondary narrative.]


Synopsis: An air carrier flight crew diverting around weather while descending over high terrain into SLVR from the southwest grew concerned that ATC was clearing them to altitudes inappropriate for the area terrain.