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FIRST ALERT: Dangerous heat and humidity, strong to severe storms all possible Wednesday

Heat Advisories already posted for portions of the Stateline
Published: Jul. 27, 2021 at 7:19 PM CDT
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ROCKFORD, Ill. (WIFR) - Thanks to an abundance of clouds taking up residence over the Stateline for a chunk of the day, heat took a brief, but welcomed break Tuesday. That said, the clouds weren’t effective in reducing the amount of humidity present in the atmosphere, and it’s appearing that humidity will only climb further on Wednesday.

With temperatures expected to reach the lower and middle 90s and dew points primed to rise well into the 70s, heat index values Wednesday are likely to flirt with or even reach triple digits during the afternoon, particularly across the westernmost sections of the area. Heat Advisories have already been hoisted for Jo Daviess, Stephenson, Carroll, and Whiteside Counties beginning around midday Wednesday, and it wouldn’t come as much of a surprise to see these advisories expanded eastward.

Heat Advisories have been posted for some ahead of another hot and humid Wednesday.
Heat Advisories have been posted for some ahead of another hot and humid Wednesday.(Mark Henderson, WIFR)
Heat indices in spots will likely be near 100 degrees in many locales Wednesday.
Heat indices in spots will likely be near 100 degrees in many locales Wednesday.(Mark Henderson, WIFR)

Skies will feature quite a bit of sunshine Wednesday, though there will be occasional cloudiness at various points throughout the day. There’s also a small chance that a few storms may ignite, due simply to the fact there’s to be so much moisture available in the atmosphere. The best chances for storms during the day will be to the west of Rockford.

A line of showers is possible late Wednesday morning into Wednesday afternoon.
A line of showers is possible late Wednesday morning into Wednesday afternoon.(Mark Henderson, WIFR)

Our greatest concerns for thunderstorms arrive well after dark Wednesday night, and especially after midnight. A line of thunderstorms will develop over eastern Minnesota and western Wisconsin during the evening, and will race southward through the Badger state. Initial projections place storms on our doorstep almost immediately after midnight and lasting into the predawn hours of Thursday.

A quick-moving line of potentially severe storms will move through the Stateline late Wednesday...
A quick-moving line of potentially severe storms will move through the Stateline late Wednesday and overnight into Thursday.(Mark Henderson, WIFR)
A quick-moving line of storms will move through the Stateline late Wednesday night into...
A quick-moving line of storms will move through the Stateline late Wednesday night into overnight Thursday.(Mark Henderson, WIFR)

There are concerning signs that this activity may evolve into a derecho, which could bring fairly widespread wind damage to the areas to the areas over which the storms travel. As such, the Storm Prediction Center highlights much of Wisconsin as being under a Level 3, Enhanced Risk for severe thunderstorms Wednesday evening and overnight. Farther south, the northeastern half of our immediate viewing area sits under a Level 2, Slight Risk for severe thunderstorms. Meanwhile, the southwestern half of the area presently is under a Level 1, Marginal Risk. By far, gusty winds will be our main threat, though a few hailstones aren’t out of the question.

It’s important to note, this risk assessment is NOT set in stone. A shift in the track of the storm by a mere 25 to 50 miles could have massive ramifications on our risk here, for better or for worse. Close attention to this developing situation is certainly warranted, and we’ll keep every set of eyes on the situation moving forward!

A higher severe risk exists into Wisconsin. Most of the Stateline is under a Slight Risk for...
A higher severe risk exists into Wisconsin. Most of the Stateline is under a Slight Risk for severe weather Wednesday night.(Mark Henderson, WIFR)
The biggest threat, by far, for Wednesday will be gusty winds.
The biggest threat, by far, for Wednesday will be gusty winds.(Mark Henderson, WIFR)

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