September weather at its best

Chicago’s September weather doesn’t get better than this: sunshine, pleasant temperatures and low humidity. That’s the story through much of the week as a huge area of high pressure sprawls across the Great Lakes Region and dominates the weather. The air mass will moderate slowly, carrying Chicago’s afternoon temperatures to 80 degrees by Friday and Saturday.

The national scene … Heavy rain

Nationally, the focus for rain falls across the Gulf Coast and, in particular, Florida. A frontal boundary that has stalled in the vicinity of the coast from Texas to northern Florida is forecast to trigger repeated bouts of rain and thunderstorms through Friday. Six to eight inches of rain swamped north and central Florida on Monday, prompting flood warnings, but several days of heavy rain lie ahead. Additional rain totals across those same areas from Tuesday through Friday are likely to bring another five to ten inches of rain.

The national scene … Heavy snow

In the West, it’s snow, and plenty of it. The higher elevations of the Teton Mountains and adjoining mountain ranges of Idaho, Wyoming and Montana can expect a 15-25 inch blanket by Wednesday.

The national scene … Frost and freezing temperatures

It’s getting to be the time of the year when Canadian air masses that drop into the Midwest and northeast portion of the country are chilly enough to bring the threat of frosts and freezes. That’s the case now. Canadian high pressure centered just northeast of Lake Huron has spread cool, dry air across the Lakes Region and New England, and nighttime temperatures are forecast to drop low enough to prompt the issuance of frost advisories and/or freeze warnings for portions of Michigan, Ohio, Pennsylvania, New York and interior New England.