A nice pretty line

An interesting satellite picture that has a very strong delineation between cold air and the warm air across the Upper Midwest and High Plains. These green IR returns are actually showing cloud cover from the soutern edge of the cold air and the clouds extend north into the cold layer. This line of demarcation bisects SD, Iowa, Illinois, and Indiana (SE to NW) and you can compare this satellite with the temperature difference on either side of the line:
Rapid City, SD is 9 and Bismark, ND is -10
Omaha, NE is 15 and Chicago, IL is -3
St Louis is 16 and Indianapolis, IN is -3


I like how clean the southern edge of the line is - it is not normally so pronounced in these sorts of scenarios - which are fairly common in the Midwest in mid-winter. The clouds are associated with the return flow of an artic high pressure over Minnesota/ND from SE to NW across the Midwest and High Plains (the clockwise rotation through the southern states and back up into the Midwest warms the air). The return flow is also interacting with a prevailing westerly flow from the Pacific which is being shunted south - see the clouds coming across B.C. and spilling down into the Rockies.