Marine Weather and Tide Forecast for Highland Park, IL

DISCUSSION
Issued at 146 PM CDT Wed Jun 24 2026

Shortwave trough over the western Great Lakes along with associated weak sfc front from northwest Wisconsin south into eastern Iowa should encourage scattered thunderstorm development this afternoon. These storms should move southeastward across our CWA late this afternoon into this evening. Jet streak is evident on water vapor imagery nosing into SE MN/SW WI early this afternoon. Guidance depicts a 40-50kt 500mb speed max spreading across southern WI and northern IL this afternoon and evening. This will result in a increase in deep layer shear into the 40kt range.

Rain associated with lead shortwave should continue to exit the area early this afternoon with at least partial clear already spreading into our far western CWA This should allow for moderate instability to develop across the area with MLCAPES of 1000-1500 J/kg. The moderate instability coupled with fairly strong deep layer shear should support supercells with a potential for large hail and perhaps damaging winds. Weak mid level lapse rates may limit the magnitude of the hail/wind threat, but the long straight hodographs would support splitting supercells and a hail threat.

This front should clear the CWA late this evening bringing an end to the showers/storms by late evening. In the wake of the front, looks for dry weather Thursday and most of Thursday night. There is a signal in most guidance for another low amplitude shortwave to potentially becoming convectively enhanced before moving toward the mid Mississippi Valley Friday.
Instability should be pushed well south of our CWA, so if this MCV takes a more northerly track it would likely be in a weakening state as it encounters more stable and drier low level air mass over our area Friday. Conversely, it is possible that the MCV may tend to propagate more southward toward the instability gradient. In collaboration with neighboring offices, lowered NBM pops for Friday some and kept slight thunder chances confined to areas south of the Kankakee/Illinois Rivers.
Cloud cover should keep temps cooler Friday, but if it does rain then highs would need to be lowered even more, especially southern CWA where better rain chances should be.

Over the weekend, an upper level ridge is progged to begin developing over the middle and lower Mississippi Valley region.
A warm front is progged to lift northward Saturday night into Sunday. Some threat of showers and thunderstorms will exist ahead of this front and ahead of the EML advecting eastward with the developing upper ridge. Medium range guidance is in good agreement in developing a fairly strong (595-596dm) 500mb ridge over the Mississippi Valley early next week.

Sunday, there's likely a small chance of showers/storms in the morning, then probably dry in the afternoon. With the warm front moving through the area, a weak lake breeze is possible along the IL shore perhaps offering a bit cooler conditions right along the lake. Elsewhere, highs should climb into the upper 80s to around 90 with higher dewpoints likely pushing afternoon heat indices well into the 90s to near 100.

Monday through Wednesday, current forecast has highs in the low to mid 90s with dewpoints in the 70s resulting in heat indices solidly over 100 degrees. Based on the current model guidance, these values are reasonable, but with the heart of the upper ridge progged to be centered south toward the lower Ohio and mid-lower Mississippi Valley it is possible that ring of fire convection currently progged to be mostly to our north could sneak farther south or send outflow south into parts of our area offering some reprieve from the heat. Harder to forecast that this far out, but something to watch as a possible spoiler to what otherwise looks like the first formidable heat wave of the summer.

- Izzi

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
Issued at 1249 PM CDT Wed Jun 24 2026

Forecast concerns include...

Scattered thunderstorms this afternoon into this evening.
Wind directions through this evening.
Northeast wind shift/lake breeze Thursday evening.

An area of showers will move across the Chicago terminals over the next few hours with brief mvfr vis/cigs and possibly begin to dissipate. Scattered thunderstorms are developing across southwest WI and this activity is expected to increase in coverage as it moves southeast across the terminals during the mid to late afternoon. There may be a second round of showers and scattered thunderstorms during the mid/late evening and while confidence is low, opted to include prob thunder mention for this potential, which may be dependent on how the first round of storms evolves. Isolated showers may linger into the overnight hours.

There are various boundaries from the current showers and earlier showers this morning that make prevailing wind directions challenging. A general west/northwest direction is expected for the next few hours and then a turn back to the southwest is expected later this afternoon. Winds may turn to the southeast or easterly behind the first round of storms, then possibly become light and variable during the mid evening.
Prevailing light westerly winds are expected overnight, turning more west/northwest Thursday with speeds to 10kt. A lake breeze is expected to develop Thursday afternoon and move inland with winds turning northeast at the Chicago terminals early Thursday evening. There is also a low chance for a few showers to develop along the lake breeze Thursday afternoon. cms

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...None.