Marine Weather and Tide Forecast for Wilmette, IL

DISCUSSION
Issued at 233 PM CDT Sun Jun 7 2026

SPC mesoanalysis depicts a stout theta-e gradient along a surface stationary front from northwest Illinois through Gary, Indiana. Luckily for the Chicago Metro, most of the activity this afternoon and evening should be along and southwest of this boundary. Storm motions are incredibly slow (to the north- northeast at 10 to 15 mph). While wet microbursts producing locally gusty winds are possible, the main hazard this afternoon is becoming a hydro concern. Instantaneous rain rates on MRMS for storms closer to the Mississippi River (where the better forcing is located) have had isolated storms producing over 2 inch per hour rates! For now, the higher rain totals have remained west of the area, but the threat for localized torrential downpours this afternoon and evening keeps the threat for flash flooding prevalent.

An upper level trough over the central Plains is expected to slowly move east through the overnight and over northern Illinois on Monday. This should eventually kick the aforementioned stationary front northeastward and produce widespread showers and storms across the forecast area tomorrow.
With the wave being more progressive in nature, the threat for flooding concerns is somewhat lower than this afternoon. But given the amount of moisture available and how efficient the rain should be produced, flooding concerns remain elevated tomorrow. Additionally, there will remain a threat for wet microbursts producing localized gusty winds. With high CAPE, weak shear, and ample ambient vorticity, a funnel cloud or two cannot be completely ruled out, particularly in the afternoon when the trough axis is overhead.

Weak ridging will grow on Tuesday from the west. Lingering showers and some isolated storms are possible in the morning, mainly east of I-55. While some afternoon summertime pop-up showers are possible, with weak forcing, the forecast for Tuesday and Wednesday is trending drier. More impactfully, this ridge will drive flow back to southwesterly and advect in a much warmer, and muggy, airmass. 850 mb temperatures are expected to increase to and potentially in excess of 20C.
Surface temperatures are expected to climb above normal into the mid to upper 80s and even the low 90s. With forecasted dew points in the 70s, heat indices are expected to climb into the mid to upper 90s each day.

That ridge axis is expected to slide eastward over the area on Wendesday as the next long wave trough sets up over the northern Plains. An upper level low is expected to deepen Wednesday night over Manitoba with a strengthening 100 knot upper level jet embedded in the trough. A reflected surface low over southern Canada is expected to develop with a cold front draped southward down the Plains. There is a lot of model uncertainty on storm development along the front on Wednesday. There is a non-zero chance that a MCS develops and arrives in northwest Illinois overnight, it would arrive in a less than favorable time of day. Models are showing a little better consistency with showers and storms developing with the better forcing with the front on Thursday. With strong low level flow, a stout upper level jet for synoptic forcing, and MUCAPE values 2000-3000 J/kg, an eastward propagating squall line may develop with strong to possibly even severe storms Thursday. Lastly, there is also a little uncertainty on temperatures for Thursday due to the front. It could set up as another hot and humid day at first, but the timing of the front may impact max temps.

Quasi-zonal flow aloft is expected to develop behind the frontal passage on Thursday. Temperatures should become slightly more muted at the end of the week. Another upper level wave may pass over on Saturday providing another chance for showers and storms over the weekend, but low confidence in timing and strength at this distance.

DK

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/
Issued at 127 PM CDT Sun Jun 7 2026

Key Messages:

- Periodic shower and thunderstorm chances exist through most of the TAF period.

- MVFR ceilings are possible tonight into tomorrow morning.

A warm and humid air mass will promote shower and storm chances through much of the current TAF period as an upper-level disturbance pivots through the region.

For this afternoon, thunderstorms are likely in the 19Z to 21Z or so time window at RFD, where torrential rainfall will also likely reduce visibilities to IFR levels or lower for a brief period of time. Confidence in thunderstorms occurring at or in close proximity to the Chicago metro terminals through this evening is lower compared to RFD, but did introduce some targeted PROB30 groups for SHRA (TSRA for DPA) during the time frame when at least isolated shower activity is most likely to percolate close by. Broad isentropic ascent within this moist and unstable air mass may then permit some nuisance shower activity to persist in the area through much of tonight. There may be a period of time tonight where shower coverage could grow large enough to warrant something more than just a VCSH mention in the TAFs, but confidence in whether this will occur and where/when is low.

The early-mid morning tomorrow appears to be the most likely time frame for little to no shower/storm coverage across northern Illinois and northwest Indiana during the current TAF period. By the late morning or early afternoon, another wave of scattered showers and storms will develop, and the expectation is for this convection to persist through the afternoon. Gusty outflow winds associated with the most robust thunderstorms tomorrow (and really, today as well) may lead to erratic wind shifts, while torrential rainfall will also cause sharp visibility reductions.

Otherwise, easterly winds today will trend more southeasterly tonight into tomorrow morning, then more southerly tomorrow afternoon. At least patchy MVFR ceilings may also move into the area late tonight or early tomorrow morning. RFD stands the highest chance of seeing prevailing MVFR (or lower) ceilings, though some chance for them exists at the Chicago metro terminals as well.

Ogorek

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