textproduct: Chicago

KEY MESSAGES

- Isolated to scattered showers and thunderstorms will continue through this evening, with the highest thunderstorm coverage remaining south of I-80. The strongest storms south of I-80 may produce strong to damaging winds and hail up to quarter size on a localized basis.

- While there will be daily shower and thunderstorm chances through the upcoming week, expect plenty of dry hours. Outside of the convective chances, it will be very warm and humid (focused away from the lake until Tuesday).

DISCUSSION

Issued at 307 PM CDT Sat Jun 6 2026

Through Sunday Night:

GOES visible satellite imagery this afternoon shows several regions of agitated cumulus in and near our forecast area. The most congested cumulus has generally been focused near the lake breeze and along a somewhat diffuse remnant outflow boundary from last night's convection that has been laid out across our far southern counties and into central Indiana, but deeper cumulus growth has also been noted within a couple of low-level confluence/convergence zones across the northern half of our forecast area. Synoptic-scale forcing remains fairly nebulous and pretty much limited to very modest isentropic upglide, but within moist and unstable summertime air masses like the one in place today, it typically does not take much for convection to get going, and that has been the case today. That said, the relative lack of large-scale ascent has kept convective coverage isolated to widely scattered thus far, and that should largely continue to remain the case through this evening.

Across our southern counties, RAP objective mesoanalysis depicts 2000-2500 J/kg of MLCAPE amidst 15-25 kts or so of deep- layer shear. This environment was just favorable enough to yield severe downburst winds and small hail in Benton County, IN with a tall storm that briefly pulsed up there a little while ago, and would not be surprised to see another instance or two of localized damaging winds and hail up to quarter size with any convective updraft cores that manage to pulse up towards the ~13 km AGL equilibrium levels south of I-80. Farther north, a more pronounced warm nose at around 600 mb may inhibit convective growth to a greater degree in the absence of stronger forcing for ascent, making it less likely for cells to grow tall enough to produce severe winds and hail there, in addition to reducing the overall likelihood of lightning. Lastly, could not entirely rule out a funnel cloud or even a landspout occurring somewhere as slow-moving cells develop along surface boundaries in this moist and unstable air mass. The latest RAP mesoanalysis depicts non-zero non-supercell tornado parameter values in a few spots, which supports this thinking.

A slight enhancement to the low-level jet this evening may allow for disorganized convection to fester across our southern counties for at least a few hours after sunset, and possibly well into the night. This convection should eventually diminish in coverage, though, as the attendant instability reservoir becomes increasingly depleted with time tonight. The resulting lull in convective activity should persist through at least mid-morning tomorrow before large-scale forcing increases toward midday as a closed-off upper-level low presently located over the southern Plains lifts northward toward our latitude and becomes sheared-out as it does so. Despite the weakening nature of the forcing associated with this disturbance, the persisting rich low-level moisture (surface dew points up to around 70F) and diurnal destabilization as surface air temperatures warm into the 80s will support another episode of convection in our forecast area into the afternoon hours. This time around, convective coverage looks to be greatest across the southwestern half or so of our CWA. Minimal deep-layer shear will also encourage tomorrow's convection to have a pulse-like character. Enough instability will be present to support a gusty wind and small hail threat with the strongest updrafts that pulse up, but subpar lapse rates and DCAPE should keep storms sub-severe.

Ogorek

Monday through Friday:

The aforementioned weakening mid-upper low/short-wave will continue to shear out Sunday night into Monday as it encounters robust ridging centered over the eastern Lakes by then. Nonetheless, weakly capped tropics- like airmass should support fairly widespread showers and at least scattered storms developing as early as midday Monday (unless debris cloudiness proves too detrimental to sufficient destabilization). Southeasterly synoptic flow and lake breeze reinforcement will keep IL shoreline locations in the 70s on Monday, while the rest of the area reaches the low- mid 80s.

Looking ahead at the rest of next workweek, there have been some guidance members with sufficiently strong mid-level ridging and low-level thermal ridging poking into the Great Lakes region for a few days of very warm (locally hot) and humid conditions. With that said, the more likely scenario is our area being on the precarious northwestern periphery of ridging centered near the East Coast. This should entail less capping and a continuation of shower and thunderstorm chances. By later in the week (Thursday or thereabouts), seasonably strong troughing from the north central US to central Canada could plausibly yield a pattern supportive of organized strong to severe convection into the region.

Note that the NBM depicted temperatures centered Tuesday through Friday (most notably on Wednesday and Thursday) are well outside of the ensemble spectrum due to likely spurious upward bias correction. Thus we will withhold from any heat messaging locally. It looks to be very warm and humid, but not hazardously so, per the current global ensemble guidance consensus.

Castro

AVIATION /18Z TAFS THROUGH 00Z MONDAY/

Issued at 1231 PM CDT Sat Jun 6 2026

Key Aviation Messages for the current TAF period:

- A lake breeze arrival this afternoon will shift winds to the east-northeast

- Isolated thunderstorms near the lake breeze this afternoon, but better chances for thunder to the south of the Chicago Metro

Currently, conditions are VFR with light southerly winds. However, A lake breeze has already started to move inland away from the lake. Winds will switch to the northeast behind it with winds 5 to 10 knots.

Isolated showers and storms are expected this afternoon. However, the better coverage of thunderstorms is expected south of a KSQI to KVPZ line. That being said, the previously mentioned lake breeze could be enough forcing to trigger convection that could develop into at least a shower if not a thunderstorm near the terminals. While confidence is lower in any one cell directly passing over a terminal, the PROB30 was converted the -SHRA mention to the -TSRA given the amount of instability present on an already warm June afternoon. Chances for showers and thunder diminish after 23Z. Light northeast winds will slowly become more easterly tomorrow morning.

DK

LOT WATCHES/WARNINGS/ADVISORIES

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