A quick look at a National Weather Service map showing the nation's percent of average precipitation since the beginning of this year reveals a trend that is beginning to stoke concerns of crop stress from the western and southwestern Plains to the eastern Corn Belt.

The good news is much of the Plains, from North Dakota all the way to south Texas, has had more moisture than normal. That sent this year's Plains winter wheat crop out of the chute on a high note. But, recent dryness has farmers worried that Mother Nature may trim the crop's yield potential.

"We could see a 10% or more reduction in that 403.9 million bushel estimate, just because we haven’t received any precipitation to speak of during the crucial flowering/grain-fill period -- the time when the crop really needs it," says Bill Spiegel, communications director for Kansas Wheat and Jewell, Kansas, wheat farmer.

"According to the U.S. Drought Monitor, as of May 1, 38.2% of the contiguous United States was experiencing drought conditions, an increase from the 31.9% at the beginning of 2012," according to a NWS report. In few places is that expanded dryness more apparent than in Missouri, where state climatologist Pat Guinan says the severe dryness is creeping north, especially in the last few days when there has been less than half an inch of rain. Now, the dryness that was focused on the Bootheel region has made it as far north as Interstate 70.