WHAT A DIFFERENCE A DAY MAKES!

Chicagoans experienced a jarring 24-hour temperature pullback of more than 30-degrees Monday afternoon—and this after the warmest weekend of 2023, including Sunday’s recording of a record-typing 87-degree high

Temps down more than 30-degrees from Sunday’s levels Monday, largely the product of winds off the 48-degree lake waters—warming returns over coming week with temps surging from 69 Tuesday to 77 Wednesday, 81 Thursday and 79 Friday but expect easterly lake breezes to cool immediate lakeshore areas each day this week. Weather dries and mixed sun appears Tuesday with lots of sun Wednesday, but wet weather returns with gulf moisture late week and this weekend.

• The southbound pneumonia front which induced Sunday afternoon and evening’s sharp pullback ignited explosive t-storm development mainly south of Chicago late Sunday into Sunday night. These storm’s lightning displays and hail production were impressive with some stunning rainfalls—like the 3.66” which fell at Grant Park in Kankakee County and the 3.23” in Will county’s Wilmington. Other impressive totals include 3.20” at Mendota, 2.80” at Carbon Hill and 2.43” at Channahon. But, while those rains were impressive, only 0.17” were reported at O’Hare and 0.12” at Midway Sunday into Monday.
• It’s worth noting that while drenching rains punctuated by strobe-like lightning displays south of Chicago both Saturday and Sunday nights, the city itself—now 8 days into May—ranks among the driest 21% of Mays on record over the past 151 years with just 0.30” of rain on the books versus the normal of more than 1” by now.

MAJOR WARMING AHEAD THIS WEEK

But, subdued on the immediate lakeshore by easterly lake winds much of the week. Thursday appears likely to be the warmest day of the week.

• Lake Michigan’s average water temp has only risen one degree in the past week (despite the weekend warmth) and now sits at 48-degree. It takes only a windshift off those chilly waters to send temperatures plummeting this time of year—witness what’s happened in the past 24 hours.
• Even as temps surge to within striking distance of 70-degrees with the return of some sunshine Tuesday (there’s been NONE today), the northeast winds predicted Tuesday will hold immediate lakeshore high temps to the low or mid 50s—and Wednesday’s lakeshore temps only in the mid 60s as inland temps soar to the mid to upper 70s.
• Thursday’s the day when temps are to surge above 80—but may hold to the 60s on the lakeshore—much as happened here Saturday.

TEMPS ABOVE NORMAL THIS WEEK, BUT MODESTLY BELOW NORMAL NEXT WEEK

A jet-stream shift out of Canada is predicted to bring a cooler weather regime into the area from Sunday into next week. While this week’s O’Hare temps are to average 8-degrees above normal. Next week may come in a degree below normal.

WET WEATHER’S BACK LATER THIS WEEK INTO THE WEEKEND

Resurgent Gulf moisture sweeps into the area Thursday night into Saturday and that will add a warmer feel to the air

• It will also ignite showers and t-storms in clusters. They won’t be continuous—they’ll come and go. But, averaging across modeled rainfalls yields totals which may exceed an inch in many areas.
• What will be interesting to monitor is another surge of cool air Sunday which could split the coming weekend between Saturday warmth inland and a chilly NE wind Sunday. Also, with winds pushing into 60-degree dew point air Saturday, this could raise the potential for lakeshore fog and haze. That’s a way off—so that’s a prediction we’ll refine as the week goes along.