textproduct: Chicago

KEY MESSAGES

- Widely scattered showers and isolated thunderstorms this afternoon, some may produce very localized wind gusts over 50 mph.

- While most of the time will be dry, there will be additional shower chances through the weekend.

- Other than one warm day Saturday, near to below average temperatures are expected through the middle of next week.

DISCUSSION

Issued at 251 AM CDT Thu May 7 2026

Vigorous shortwave noted on water vapor imagery over the Dakotas early this morning. Blossoming ACCAS noted on nighttime microphysics GOES RGB imagery in advance this feature, an indication of both ascent and as well as some mid-level moisture. This feature will zip east-southeastward across the mid-Mississippi Valley today and impact our weather this afternoon.

Low level air mass in advance of this wave is very dry with sfc dewpoints mostly in the 20s across northwest IN, the northern half of IL, and points north and west. Forecast soundings this afternoon show a very deeply mixed boundary layer and pretty classic High Plains looking inverted V soundings. Despite the deeply mixed and dry boundary layer, some mid level moisture and ascent associated with a developing 60-70 kt H5 jet streak should trigger scattered high based convection across northern/central IL into northwest IN this afternoon. Very cold air aloft will augment the dry boundary layer to allow for a few hundred J/kg of surface based CAPE this afternoon. Equilibrium levels well above -20C could support a few lightning strikes with this activity this afternoon and have introduced a slight chance of thunder today. With or without lightning, any high based convection developing today will be capable of producing isolated dry microbursts capable of producing very localized gusty winds over 50 mph. The best chances of more robust high based convection looks to be near/south of I-80.

A few showers may linger into Thursday night across our southern CWA before the next northwest flow shortwave races into the area Friday. Still some latitudinal difference in guidance with respect to the track of Friday's shortwave trough with the EC/GFS farther south and the NAM farther north. The GFS/EC would keep the best rain chances south of I-80 while the NAM would support rain up to almost the WI border. The global models often handle these type of low amplitude waves better and have continued to carry highest pops across our southern CWA Friday, though do maintain some 20-30% chances north of I-80 in deference to the NAM's more northerly solution.

Still looks like gusty southwest winds and strong warm air advection in advance of the next clipper should result in a breezy and warm day Saturday. The farther north track of this shortwave Saturday may keep the stronger, deeper synoptic lift north of our CWA, leaving just weaker, more shallow ascent associated with low level frontal convergence. Given the fairly dry air mass in place and potential that low level moisture may tend to mix out some Saturday, our rain chances with this weekend system are looking a bit iffier. NBM pops have come down considerably in recent runs and there really didn't seem to be a compelling case to make any upward adjustments at this time. The better rain chances with the front may tend to be again south of I-80 as it encounters ever so slightly better moisture.

Another reinforcing shot of seasonably cool air will follow the front Saturday night and result in a swift return to somewhat below average temperatures Sunday into the beginning of next week.

- Izzi

AVIATION /06Z TAFS THROUGH 12Z FRIDAY/

Issued at 104 AM CDT Thu May 7 2026

Key Messages:

- Scattered showers will pass through the area this afternoon, and there is about a 30% chance that they will pass directly over the terminals.

- Breezy westerly to west-southwesterly winds are expected this afternoon.

An upper-level disturbance will drop through the area this afternoon and will be accompanied by scattered showers. High- resolution model guidance generally favors the bulk of this shower activity remaining south of the terminals, but enough spread/uncertainty remains to warrant maintaining the inherited PROB30 groups for -SHRA. The most robust showers could spit out 30+ kt wind gusts and possibly even produce isolated lightning strikes, but this activity is also favored to stay south of the terminals (there is roughly a ~15-20% chance of a lightning strike occurring near any particular airport).

Otherwise, breezy westerly to west-southwesterly winds with gusts mainly in the 20-25 kt range are expected to begin during the mid to late morning and continue through the afternoon. Occasional gusts to around 30 kts may also occur at times. Outside of any temporary visibility reductions caused by showers, dry air in the lowest levels of the troposphere will help maintain prevailing VFR conditions through the TAF period.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES

IL...Frost Advisory until 8 AM CDT this morning for ILZ003-ILZ004- ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019- ILZ020-ILZ021-ILZ103-ILZ105-ILZ106-ILZ107-ILZ108.

IN...None. LM...None.