Chilly Air on the Way - More than a Taste of Fall

Cooler air is spreading south out of Canada into the Northern Plains to the Great Lakes today. A cold front has stalled from northern Kansas to Missouri and Illinois while the front continues to spread east to the lower Great Lakes and New England. The map below shows “streamlines” - a snap shop of the air flow at 6:00 p.m. CDT. Notice the streamlines converging along the boundaries in the middle of the nation. Overrunning of warm moist air from the south over the cool air arriving from the north will spread a large area of rain over the central part of the nation. The cooler air will back up against the Front Range of the Rockies with rain and snow likely. (Check local forecasts for details in your area.) Check the WxBlog to see how clouds were changing over northeast Iowa.

A large surface low is located over the James Bay area of northeastern Canada. See the post from this morning to see the temperature differences in the converging air masses. Also the photos below show the change in clouds over northeastern Iowa during the day as lift and arriving moisture thicken clouds leading to a broad area of rain.

This chart was generated by Digital Atmosphere. The software may be purchased at www.weathergraphics.com. The fronts and high and low pressure areas are shown. The streamlines are also shown. Streamlines show the direction of air flow as a snapshot in time.