Marine Weather and Tide Forecast for Joliet, IL

DISCUSSION
Issued at 311 PM CDT Thu May 22 2025

Through Friday Night:

A pronounced shortwave trough continues to dive across the western Great Lakes which will allow isolated to widely scattered showers to persist through early evening. The bulk of these showers should remain along and south of a Peru, IL to Rensselaer, IN line with those north of this line likely staying dry. Otherwise, partly to mostly cloudy skies to gradually clear out overnight with temperatures cooling into the lower to mid-40s. Additionally, winds and waves at area beaches will also gradually subside this evening but in the meantime continue to use caution if along the lake.

A surface high will build into the area on Friday resulting in dry conditions. However, continued northwest flow aloft will keep below normal temperatures around with highs in the lower to mid-60s and lows Friday night in the lower to mid-40s. The exception will be along the lakeshore where a lake breeze will keep highs more into the mid to upper 50s.

Saturday through Thursday...

The aforementioned surface high is forecast to remain over the Great Lakes through our Memorial Day weekend resulting in mostly dry and below average conditions. Though, a stalled baroclinic zone across the mid-Mississippi and Tennessee Valleys may allow an isolated shower to brush our far southern CWA (south of US-24) on Sunday and/or Monday. Regardless, highs will remain in the 60s (50s near the lake) and lows in the 40s through the weekend.

For Tuesday onward, the forecast become much more uncertain as guidance shows an inverted upper trough developing over the Great Lakes and getting blocked in place by a ridge to our west.
Depending on where exactly this trough sets up, our area could see a warming trend with highs back towards the 70s and increasing chances for showers and/or thunderstorms or another period of below average temperatures with highs in the 50s to 60s. Given how global guidance tends to struggle with blocking patterns, saw no reason to deviate from the NBM forecast which is favoring the warmer and possibly wetter solution. That said, this part of the forecast will likely change as we get closer to be sure to check back for more details.

Yack

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/
Issued at 1229 PM CDT Thu May 22 2025

Aviation concerns for the 18Z:

- Brief MVFR ceilings for ORD/MDW early this afternoon.

- Generally northerly winds this afternoon and Friday, though lake breeze has already shifted ORD/MDW northeast and expect another early afternoon northeast shift for those sites Friday.

Forecast area remains within a region of cyclonic northerly low-level flow, to the west of a slowly-departing low pressure system over the eastern Great Lakes. Lake-enhanced surface trough has just moved through both ORD and MDW shifting winds to the northeast, and these will persist this afternoon before diminishing this evening and becoming light/variable overnight.
Winds should become light north-northwest after sunrise Friday (though model guidance shows some spread with exact directions), before another relatively early lake breeze shifts winds northeast for ORD/MDW/GYY midday/early afternoon.

Extensive area of diurnally-enhanced cloud cover has resulted in redevelopment of MVFR cloud bases this morning, but these should lift quickly to VFR early this afternoon as drier low- level air spreads in from the north. VFR conditions are then expected for the remainder of the forecast period. A few spotty showers are possible this afternoon mainly south/southwest of the terminals.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES
IL...Beach Hazards Statement until 10 PM CDT this evening for ILZ103-ILZ104.

IN...Beach Hazards Statement until 1 AM CDT Friday for INZ001- INZ002.

LM...Small Craft Advisory until 10 PM CDT this evening for Wilmette Harbor to Calumet Harbor IL.

Small Craft Advisory until 1 AM CDT Friday for the IN nearshore waters.