CALGARY, Alberta, Dec 3 (Reuters) - Canadian light synthetic oil strengthened in the cash market on Monday despite tight pipeline capacity to key refining markets, with cash sources unable to say why the market improved.

Light synthetic for January delivery was last quoted at 50 cents a barrel under West Texas Intermediate, compared with $2 a barrel under WTI on Friday, according to Shorcan Energy Brokers.

Earlier in the session, synthetic fetched a 50-cent premium. It was last priced at more than WTI at the end of October, but Canadian crude has been pressured over the past month by tight pipeline capacity and outages at some big refineries.

Enbridge Inc said last week that its pipelines between Canada and the U.S. Midwest would be 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.

Prices for heavy oil weakened. January Western Canada Select heavy blend was quoted at $29.25 a barrel under WTI, down $1.50 a barrel from Friday's settlement.

(Reporting by Jeffrey Jones; Editing by Bob Burgdorfer) Keywords: MARKETS CANCRUDE/

(jeff.jones@thomsonreuters.com)(Twitter @jeffmjatreuters)(+1 403-531-1624)(Reuters Messaging: jeff.jones.thomsonreuters.com@thomsonreuters.net)

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