Cool temperatures to persist, especially along lake
Under cool Canadian-source high pressure, clear skies and light winds may allow widespread frost across portions of the Chicago area early Sunday morning, and conditions could be repeated early Monday morning as well. As the upper-air blocking pattern responsible for our recent cooling trend weakens briefly, the high pressure will modify slowly in the next few days, with winds shifting more to the east and southeast.
Perhaps the warmest days coming up look to be Tuesday and Wednesday, when a warm front may creep far enough north to bring 70s to our southern sections, but along with that will come cloudiness and an increased chance of showers. The latter half of the week, the upper-level blocking pattern aloft is expected to reassert itself with broadening low-pressure troughs digging in along the West and East coasts, in turn confining the warm air south of the Ohio River while positioning the Chicago area in a prolonged period of cool east-northeasterly winds off Lake Michigan.
For the week, high temperatures at our official O’Hare observing site will average five to 10 degrees below normal, with individuals residing along the lakefront expected to almost daily experience a narrow range of temperatures from the upper 40s to middle 50s.