* Light synthetic quoted at $1.40/bbl over WTI
* WCS quoted at $29.50/bbl under WTI
* Sources say Syncrude cuts Dec output by 400,000 bbls
CALGARY, Alberta, Dec 5 (Reuters) - Canadian light synthetic oil strengthened on Wednesday on word that Syncrude Canada Ltd reduced forecast production in December due to the impact of cold weather on equipment at the northern Alberta operation.
Light synthetic for January delivery was last quoted at $1.40 a barrel over benchmark West Texas Intermediate crude, compared with a settlement of $1 barrel over WTI on Tuesday, according to Shorcan Energy Brokers.
Synthetic, derived from the Alberta oil sands, has strengthened all week after selling at a discount over WTI over the previous seven weeks due to refinery outages and tight export pipeline capacity.
Syncrude told customers that output this month would be down from forecast volumes by 400,000 barrels as cold weather affected operations, trade sources said.
Other oil sands operators, including Canadian Natural Resources Ltd, Suncor Energy Inc and Husky Energy Inc all said they their operations were running normally. Royal Dutch Shell was not immediately available for comment.
Heavy crude prices weakened, meanwhile. Western Canada Select heavy blend for January fetched $29.50 a barrel under WTI, a 25 cent wider spread than Tuesday's settlement.
Heavies have been under heavy pressure in recent weeks.
Enbridge Inc's pipelines are apportioned by 5 percent to 14 percent for December. Space on Kinder Morgan Energy Partners' Trans Mountain pipeline to Vancouver from the Edmonton area is also heavily rationed.
The weakness has occurred despite the restart of units at the Borger, Texas, refinery, which has been undergoing maintenance since September. The plant, co-owned by Phillips 66 and Cenovus Energy Inc, can run 35,000 barrels a day of heavy crude.