Sunday forecast: Cool and cloudy around Chicagoland, but warmer temps ahead

Sunday is May 4, but warm and sunny weather won’t be with us, at least around Chicagoland.

Sit tight, though: The return of the sunshine isn’t far off.

As for Sunday, we’re looking at cool and cloudy conditions, with high temperatures only in the mid-50s inland and the lower 50s along the lake. That’s about 10 degrees cooler than normal for this time of year.

There’s also a band of morning showers in far southern Chicagoland and Northwest Indiana that will actually follow an uncommon east-to-west path, creating the chance for showers in other parts of Chicagoland later Sunday afternoon.

If you’re looking for any peeks of sun around the area, your best bet is in far northern areas.

Conditions begin to clear on Monday, however, and temps look to be more seasonably warm throughout the week, leading up to highs in the 70s in the early Mother’s Day weekend forecast (see more below).

Here’s more behind what’s going on this weekend and what we’re expecting this week:

Why so cool this weekend?

The culprit behind the current weather pattern of extensive cloudiness, cool weekend temperatures, and occasional showers?

Two cut-off lows: One will spin across the Ohio River Valley and the other will be across the Southwest over the next several days. They sit beneath a ridge due to “Rossby wave breaking,” typical in spring as the jet stream slows down and is more inclined to buckle or retrograde. 

“Rossby wave breaking” refers to the phenomenon where large-scale atmospheric waves tend to break and distort their shape, leading to significant impacts on the overall weather pattern and climate, particularly in the mid-latitudes. This breaking process can cause air mass mixing between high and low latitudes, influence precipitation patterns, and even contribute to extreme weather events like heat waves and floods.

This results in a cool pattern, with added clouds. Also, the Canadian air is advected southward around the mid-level trough circulations. 

Rainfall forecast

Despite the cool, cloudy conditions, rainfall totals are expected to remain light around Chicagoland through the weekend.

The heaviest rainfall totals cumulatively will fall across the Ohio Valley and into portions of the Eastern U.S.

Believe it or not, we could actually use some more rain in Chicagoland right now, especially in northern counties, where drought conditions are starting to creep up.

Temperature anomaly through mid-week

A cooler than normal pattern across the nation’s midsection is tied to the “cut-off” low pressure system.  

Temperature outlook

Temperatures will gradually warm, however, for almost everyone by the end of this forecast period. By late in the coming week, almost 300 million U.S residents will see at least 70-degree temperatures, with 70s nearly coast to coast.

Forecast temperature anomaly: May 9-15

The blocking pattern breaks down, and as a result warmer temperatures take hold across the Midwest and Eastern U.S.

Eta Aquarid meteor shower

The Eta Aquarid meteor shower, remnants of Halley’s comet, peaks this weekend and into next week.

8 p.m. sunset approaching

Daylight continues to lengthen, with the first 8 p.m. or later sunset only days away in Chicagoland!

May’s warming trend

Normal highs rise from 65 degrees on May 1 to 76 degrees by the end of the month, as we continue to move closer to summer.

We’ll see some of that warming trend this week, with the early forecast for the coming Mother’s Day weekend looking quite pleasant, as of now.