textproduct: Chicago

KEY MESSAGES

- Scattered thunderstorms will move through the area overnight and may produce strong to locally damaging winds and a few instances of hail.

- Rain is likely late Tuesday into Wednesday, and there is also a chance for thunderstorms during this time period.

DISCUSSION

Issued at 136 AM CST Sat Mar 7 2026

Through Today:

Warm air advection and broad upper-level diffluence beneath the right entrance region of an anticyclonically-arcing jet over the Upper Midwest has fostered the development of a broad swath of convection that is beginning to enter our western counties at press time. The overall intensity of this convection has been held in check thus far by a stabilized planetary boundary layer and fairly muted instability, with a special 04Z RAOB from DVN depicting a thermodynamic profile that isn't particularly favorable for widespread severe thunderstorms.

However, both this RAOB and regional VWPs have sampled some fairly strong flow above the somewhat shallow near-surface stable layer, and evidently, some of this flow that is coincident with the ongoing convection has been able to penetrate its way to ground level -- presumably with the assistance of evaporational processes induced by a fair amount of dry air in the low- and mid-levels. Recently, several 50+ mph peak wind gusts were observed in the Quad Cities metro beneath an area of fairly innocuous radar reflectivity, and would suspect that similar gusts may be observed over the next few hours as this area of steady rainfall with embedded lightning continues to progress northeastward. Have issued a Special Weather Statement for our western counties to highlight this possibility, and it's possible that additional products may need to be issued farther to the east if this stronger flow aloft continues to find a way to get transported to ground level.

Otherwise, the more robust-looking (though still somewhat disorganized) multicell thunderstorms farther to the south don't appear to have much of a clear pathway to organize and intensify appreciably given the less-than-favorable thermodynamic environment. That said, there are some hints of a potential MCV developing, and these storms may still nevertheless have the capability to produce strong to locally damaging winds given the strong ambient flow aloft, so we'll continue to monitor radar trends and surface observations closely. A few instances of small hail may also occur with these cells as they pulse up periodically.

It appears that most of the thunderstorm activity should clear our CWA (save for maybe our far eastern counties) by around or shortly after sunrise. As we dry out behind the back edge of the associated rain shield, there could be a few hours-long period later this morning and early afternoon when some stronger southwesterly gusts -- perhaps approaching 40 mph at times -- are observed before a well-defined cold front sweeps through the area from west to east. The timing of this cold frontal passage will result in many locations observing their high temperatures for today during the morning hours, with temperatures expected to fall quickly into the 40s behind the front. A thin line of strongly-forced showers may also accompany the front. Don't think that we'll be able to destabilize enough for this to cause any sort of funny business amidst the enhanced low- and mid-level kinematics, but if surface temperatures end up being a few degrees warmer than currently anticipated, then this might be something that we'll need to keep a closer eye on.

Tonight through Friday:

After today's cold front clears the area, drier conditions are expected for the remainder of the weekend and into Monday as two northern stream waves zip eastward to the north of our area. Breezy southwesterly winds will help yield unseasonably mild temperatures on Sunday that look to moderate to potentially near-record levels on Monday. The second of the aforementioned disturbances will then send a cold front into the area sometime Monday night into Tuesday which will likely stall out somewhere in or near our forecast area as it encounters reinvigorated south-southwesterly breezes during the daytime on Tuesday. Thus, there is a fair likelihood that there will be a sharp (potentially 15-20+ degree) temperature gradient laid out across our CWA on Tuesday, with unseasonably warm/near-record temperatures persisting south of the front and more seasonable temperatures being observed north of the front.

Tuesday into Wednesday, an initially cut-off upper-level low meandering over the southwestern CONUS and northwestern Mexico will begin to make more meaningful eastward/northeastward progress and attempt to phase with an amplifying northern stream wave somewhere over the central CONUS. As these two disturbances arrive, anomalously high Gulf moisture (characterized by potentially record high precipitable water values, per SPC sounding climatology for ILX) is expected to surge northward into the Lower Midwest and southern Great Lakes. Widespread precipitation is thus likely to be observed in the region Tuesday into Wednesday. Rain should be the predominant precipitation type observed in our area, but ensemble guidance depicts several potential scenarios where thermal profiles in at least our northern counties end up becoming cold enough to support the occurrence of some type(s) of wintry precipitation before the precipitation comes to an end on Wednesday.

Existing ensemble spread in the timing and degree of any potential phasing between the two incoming disturbances, in addition to persisting uncertainties regarding the placement of the aforementioned low-level frontal zone, preclude having much confidence in more specific forecast details for Tuesday into Wednesday at this time. However, the modeled influx of unseasonably high moisture content, the ensemble signal (particularly from the EPS and CMCE) for instability to build into our area, the presence of a sharp baroclinic zone in the region, and probabilistic output from multiple machine learning/AI models all suggest that the late Tuesday into early Wednesday time frame will be one that will need to be monitored for potential severe thunderstorms and flash flooding in the region.

Ogorek

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 528 AM CST Sat Mar 7 2026

Forecast concerns include...

Low mvfr cigs through this afternoon. Possible ifr cigs this morning. Showers through early afternoon. Gusty westerly winds through this afternoon.

Showers will continue to slowly move east through mid morning with additional showers possible late morning into the early afternoon, which would be along and ahead of a cold front which will move across the area this afternoon.

Vfr cigs currently are expected to lower through mvfr over the next few hours and then prevailing low mvfr cigs are expected into this afternoon, likely scattering out this evening. There is also the potential for ifr cigs this morning and possibly along the cold front. There is still uncertainty for ifr cigs, but have included tempo mention with this forecast.

Southwest winds will turn more west/southwest over the next few hours and then shift west/northwest with the cold front. Gusts will increase into the 25-30kt range this morning and continue into the afternoon, steadily diminishing with sunset this evening. Southwest winds will then increase Sunday morning with gusts into the lower 20kt range by late morning Sunday.

There is a low chance for patchy fog late tonight into early Sunday morning. Confidence is too low to include any mention with this forecast by trends will need to be monitored. cms

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until noon CST today for the IL and IN nearshore waters.