Corn and soybean futures look to start Tuesday's trading session higher, while wheat still has some weakness to deal with, sources say.

Early calls for the grains for Tuesday's session are corn 2-4 higher, soybeans 3-5 higher and wheat 1-3 lower, according to private sources.

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The grains closed out last week on a higher note, and many think that this week could see that rally continue, largely because of continued concerns about the crop weather in South America.

• Read more: 'Wild' post-holiday trade expected

So, if the trade is 'wild,' how high could it go? It's likely to continue to be a slower, light trading week (as is typical of the week between the Christmas and New Year's holidays), so that could mean that it may not take much for a major move.

"Since we have been rallying up for the last week are we going to take out $12 barrier for January soybeans due to weather in South America? Or are we just going to trade between $11.70 to $11.50?" says Agriculture.com Marketing Talk frequent contributor giolucas. "There are a lot of people on vacation but the thin trade can make things move in either direction."

• Talk: Could soybeans take out $12 this week?