textproduct: Chicago

KEY MESSAGES

- Dangerous swimming conditions at Indiana Lake Michigan beaches through this evening, then possibly again Thursday.

- Severe thunderstorms are possible Tuesday afternoon and again Wednesday. However, Wednesday is currently the day of most concern for severe weather in, or very near, our area. Heavy rain and flash flooding is also possible with the storms on Wednesday.

DISCUSSION

Issued at 250 PM CDT Sun Jun 14 2026

Broad mid and upper-level troughing (anchored by a Hudson bay area low) will foster an unseasonably strong belt of west- northwesterly mid and upper-level flow oriented from the northern Plains, east- southeastward into the the lower Great Lakes region through much of the week. This pattern will essentially steer two notable weather impulses across our region through midweek, with associated shower and thunderstorm chances, particularly on Tuesday and again on Wednesday. Both days will carry a threat of heavy rain, along with the potential for some strong to severe thunderstorm threat, though Wednesday continues to be the day of most concern for severe weather and potential heavy rain and flooding.

Prior to our potential periods of active weather, Monday is expected to be another quiet and pleasant weather day across the area. Dry weather can be expected with temperatures topping out in the mid 70s under partly cloudy afternoon skies. Thereafter, our chances for showers and thunderstorms will increase, particularly during the day on Tuesday as the first impulse shifts over the region. As it does, an associated weak surface cold frontal boundary is expected to shift eastward across eastern IL into northwestern IN late in the day. Low-level moisture return is expected to remain somewhat muted ahead of this frontal boundary, owing to remnant surface ridging across the deep south blocking Gulf moisture trajectories. Accordingly, prefrontal surface dewpoints and associated instability are expected to remain modest (upper 50s to low 60s). Nevertheless, the presence of ~50 kt mid-level westerly flow overhead Tuesday afternoon should support some storm organization, and thus the potential for a few strong to severe storms. Currently, it appears the primary threat with any storms would be strong damaging wind gusts, and possibly some hail. This threat looks to be favored mainly across eastern IL into IN, similar to the region highlighted in a level 1 of 5 severe threat in the SPC Day 2 outlook.

The shower and thunderstorm threat should diminish quickly Tuesday evening as the main impulse and surface boundary sweep east of the area. However, our next weather maker will be quickly taking shape across the northern Plains Tuesday night. Model and ensemble guidance remain in agreement that an unseasonably strong surface low (potentially into the low 990s mb) will track eastward across t he Upper Midwest and into the western Great Lakes region late Wednesday into Wednesday evening. As it does, a strong southerly mass response is likely to result in a northward surge of deeper Gulf moisture into the Midwest as a surface warm front shifts northward across IL. Daytime heating of the airmass south of this warm front is expected to result in moderate to strong instability in the presence of a strongly sheared environment. Accordingly, as severe thunderstorms will be a big concern Wednesday afternoon and evening, particularly across parts of the Midwest into the lower Great Lakes region.

Locally, there remains some question as to how far north this severe threat may extend Wednesday afternoon and evening, particularly considering our area does look to be along the northern periphery of the better severe weather threat expected across the Midwest. Nevertheless, Wednesday afternoon and evening is a period we will be watching closely. In additional to the severe threat, deep Gulf moisture (PWATs near 2") will also support very heavy rainfall with these storms, and with our area likely to reside near the surface warm front where storms could move over the same areas, the threat of flash flooding will also need to be monitored closely.

A period of breezy northwesterly winds and cooler weather looks in store for the area again for a period later in the week following Wednesday's system. These breezy northwest winds on the lake into Thursday may support build waves and the need for another beach hazard statement for northwest IN Lake Michigan beaches.

KJB

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 623 PM CDT Sun Jun 14 2026

Aviation forecast concerns for the 00Z TAFs:

- Very low (5-10%) chance for a north-northeast lake breeze wind shift at ORD/MDW this evening.

Early evening surface analysis depicts high pressure building southeastward from the High Plains, in the wake of last night's cold front. Breezy northwest winds persist across the terminals at issuance time in the tighter surface pressure gradient on the eastern periphery of the high, but will diminish with sunset this evening. Only concern for the terminals (ORD/MDW specifically), that wind directions near/over Lake Michigan are more northerly, and as surface winds diminish this evening there is a low chance that these northerly winds may attempt to push a lake breeze boundary inland. None of the available high-res wind guidance explicitly depicts this, though it will need to be monitored as it could result in a wind shift to the northeast. MDW is likely more susceptible due to its closer proximity to the lake and the shape of the shoreline north of Chicago.

Otherwise, winds will diminish and become westerly overnight (light southwest at RFD), before becoming slightly breezy again on Monday with gusts 15-20 kts. This should prevent any lake breeze impacts for ORD/MDW. VFR conditions are expected to prevail.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...Beach Hazards Statement until 10 PM CDT this evening for INZ001-INZ002.

LM...None.