Marine Weather and Tide Forecast for Niles, IL

DISCUSSION
Issued at 130 PM CDT Mon Aug 3 2026

High pressure currently centered over Illinois is progged to slowly move east to New England by Tuesday afternoon. The ridge axis may be close enough to the area still tonight to allow for some patchy ground fog to develop, especially across rural areas of northwest Indiana in closer proximity to the surface ridge. Fog and low cloudiness isn't expected to be nearly as widespread as it was this morning, but opted to include some patchy fog in the grids over far southern and southeastern portions of the CWA Tuesday's weather will be similar to today's; partly cloudy and warm with rather comfortable humidity levels. While there may be a lake breeze again Tuesday afternoon, a bit more of a southwesterly gradient should limit the inland extent and likely confine it to the IL shore.

Attention will turn to the trough currently over the northern Rockies. This trough is expected to translate eastward across the northern Plains and into the upper Mississippi Valley by mid week.
At the surface, a cold front currently across the central into the northern Plains will gradually move eastward in concert with the upper trough and into the Midwest. While high pressure to our south across the Gulf Coast states should limit access to Gulf moisture, there is a reservoir of moisture pooled ahead of this front with widespread dewpoints in the 70s and PWATs 1.75" to nearly 2". As the front settles southeastward toward our region, so too should this axis of richer atmospheric moisture.

Unfortunately, there will likely be several smaller scale vorticity maxima embedded within the broader trough, which could complicate prediction of the timing and placement of better convective and heavy rainfall chances, especially as these small embedded shortwaves potentially become convectively enhanced. There is a signal in guidance that one such wave will support convection developing over the Cornbelt region Tuesday afternoon, with most guidance suggesting this activity could persist through the night and arrive in our northwestern CWA late Tuesday night/early Wednesday morning in a weakening state. Extensive cloud cover and potentially rain with this feature is expected to overspread especially the northern half of our area Wednesday morning with cloud cover and potentially showers lingering into the afternoon, limiting potential heating/destabilization.

Global models are in pretty good agreement in depicting another embedded shortwave trough supporting more widespread convective development Wednesday afternoon across the southern Cornbelt/lower Missouri River valley. This, potentially convectively enhanced vort, is then expected to track eastward into Illinois Wednesday evening leading to an increase in coverage and intensity of rainfall. Given the high PWATs pooled ahead of this boundary; heavy rainfall would certainly be a threat, but there are a lot of moving pieces to this atmospheric puzzle, so forecast confidence is still on the lower end of the spectrum regarding where and ultimately if a heavy rainfall/flooding threat will materialize in our area. If a sizable MCS does roll across the area Wednesday night, that would likely push the effective surface boundary south, potentially out of our CWA This could result in better rain chances Thursday ending up south of I-80 or potentially farther south into central Illinois.
For now, given the lower confidence, I didn't stray from the aggressively high precip chances in the NBM for Thursday, but if confidence increases in a formidable MCS moving across the area Wednesday night, then the focus for redevelopment Thursday could end up much farther south.

Mainly dry and seasonably warm weather is expected late in the week through much of the upcoming weekend. There are indications in the medium range guidance that we could get into a potentially more active northwest flow regime heading into next week with thunderstorm chances returning.

- Izzi

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
Issued at 1207 PM CDT Mon Aug 3 2026

A large surface high pressure system will continue to meander through the region today leading to generally light and variable winds. The weak surface pressure gradient is allowing for a lake breeze to push inland, which will lead to a northeasterly wind shift at ORD/MDW within the next hour or two and DPA later this afternoon. Otherwise, winds will return to a light and variable regime overnight. After daybreak, winds will trend southwesterly and increase in magnitude toward 10kt by late morning.

Scattered MVFR cigs based near 2500ft will rise to 3500ft this afternoon and scatter behind the aforementioned lake breeze.
Pockets of fog may develop near RFD/DPA/GYY overnight, but will keep mention out of the TAF for now given low confidence in timing/placement.

Borchardt

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