"North Carolina in Every Respect the Opposite of Pennsylvania: On the
day Pennsylvania Democrats vote in a primary that has seen opinion
polls fluctuate wildly on how big her possible win might be, North
Carolina Democratic Primary voters are steady-steady, and not with
Clinton on top, but Obama. Obama's advantage has fluctuated
imperceptibly, or not at all, in four tracking polls conducted over the
past 90 days. Today, 14 days till NC votes are counted, Obama leads by
9 points. In five previous tracking polls, going back to before the
Michigan Primary, Obama's lead has been 4 points, 10 points, 8 points,
10 points. NC men are stable. NC women are stable. Voters under age 50
are stable. Voters age 50+ are stable. Black voters are stable. White
voters are stable. Charlotte voters are stable. Moderates are stable.
Registered Democrats are stable. Unaffiliated voters are stable." 
http://www.surveyusa.com/client/PollReport.aspx?g=7e1ed059-9ef0-4a2c-a2a6-3cbef8ca9803


In NC the AA vote is expected to be over 40 percent.
In NC the 18-34 vote is expected to be higher then the 65+ vote, very different then PA.   
The amount of voters who have college education in the democratic primary in NC is also much higher in NC.  There has been a large increase in voter registration in the last few months, mainly with AA and the youth vote.   
Many polls are showing Obama running just slightly under Hillary with white voters overall. 

So with High AA and Youth and Educated = Obama wins, it also helps that pretty much everyone has endorsed Obama in NC.