Marine Weather and Tide Forecast for Evanston, IL

DISCUSSION
Issued at 208 AM CDT Tue Oct 13 2026

Though Tonight:

A recent hand surface analysis revealed a 1003mb surface low pressure system centered over southern Wisconsin. A sharp cold front extends southwestward through central Iowa and into the central Plains toward a secondary surface low centered near the Colorado and Kansas border. In the warm sector of the Great Lakes cyclone, it is an unseasonably warm night with current temperatures at press time in the mid 70s (some 10 degrees warmer than typical high temperatures this time of year). A strong low-level jet (50-55kt at about 3000 feet AGL per the KLOT VWP) is maintaining a few southwesterly surface gusts of 15 to 20 mph early this morning, as well (the Chicago Crib is gusting to nearly 40 mph). Taking a step back, the large-scale pattern is being driven by a strong Pacific trough digging toward the four Corners Region, leading to quasi-zonal flow across the central and eastern United States. Over the next 72 hours, the local weather will be influenced by the trough as it evolves eastward with time.

Based on the current location and speed of the cold front, it should move across our local area just after daybreak. Low-level cold air advection doesn't look particularly noteworthy in our area behind the front, a consequence of a low-level pressure col developing between the departing low pressure system toward the northeastern US and the surface pressure falls in the Plains.
In fact, the front may very well stall somewhere near US-24 by early afternoon, transitioning into more of a stationary front ahead of the trough moving through the southwestern United States. Nevertheless, today is still shaping up to be another unseasonably warm day with highs in the upper 70s near the Wisconsin state line, around 80 near the I-88 and I-80 corridors, and mid to locally upper 80s in closer proximity to the frontal boundary near US-24. Will have to watch for a sprinkle or two from mid-morning to early afternoon near the front as a plume of modestly steep mid-level lapse rates (around 7 K/km per the 00Z OAX RAOB) coincident with a pocket of mid- level moisture (area of ACCAS currently over eastern Nebraska and western Iowa) slides through northern Illinois. Given a residual pocket of dry low-level air across the area (notably below 700 mb, see the 00Z DVN RAOB), will keep the chance of measurable precipitation in the 5 to 10% range, again largely south of I-80.

This evening and tonight, the dominant Pacific upper-level trough will propagate toward the Four Corners region establishing southwesterly low- to mid-level flow from the southern Plains toward the Lower Great Lakes. The tightening low-level baroclinic zone across the middle Mississippi River Valley (partially forced by a building surface high in the northern Plains) beneath a parade of upper-level shortwaves will support the development of several clusters of showers and thunderstorms. The current expectation is for the most robust activity to remain tied to the highest-quality low-level moisture near and south of the front generally from central Kansas to central Illinois, through still do expect a healthy coverage of showers and storms as far north as the I-88 corridor from the evening through the overnight hours. Relatively high freezing levels (near 14,500 ft AGL) and modest/skinny CAPE profiles to limit updraft intensity (weak lapse-rates) should otherwise offset a favorable kinematic/shear profile for hail.
And while the upper-level flow does look extremely unbalanced, any synoptic-scale gravity wave formation should tend to be offset well north of the instability axis likely mitigating a GWAC/damaging wind threat. As a result, current expectations are for the thunderstorms tonight to be fairly generic with the common threats of downpours, occasional lightning strikes, and pea to dime size hail. Coverage of activity should wane markedly by daybreak Wednesday.

Wednesday into Wednesday night:

On Wednesday, the northern Plains high pressure system will slide eastward beneath rising mid-level heights as the Pacific trough moves toward the central Rocky Mountains. An increase in east-northeasterly flow on the southern side of the surface high pressure system will shunt the low-level baroclinic zone southward. Trapped low-level moisture beneath a persistent inversion as well as a steady stream of high clouds from convection to our south will maintain cloudy skies throughout the day. In fact, would not be surprised to see some areas of drizzle particularly in the morning before dry air advection allows for the low-level moisture depth to shrink through the afternoon hours. Taken altogether, opted to undercut NBM temperatures for Wednesday and instead advertise highs in the low to mid 60s to perhaps around 70 near the US-24 corridor.

Wednesday night into Thursday night:

Wednesday night into Thursday, ensemble model guidance is in fair agreement that the trough in the central Plains will phase with a northern-stream trough diving southeastward out of Canada. Even with the usual variance in exactly how the systems phase, there remains a persistent signal for disorganized pressure falls in the Plains to merge into a coherent surface low which would be poised to rapidly deepen while lifting northeastward close to or directly over our area on a path toward southeastern Canada. Taken together, do expect periods of showers and a few thunderstorms focused on Thursday as the surface low moves through the area, which is reflected in NBM PoPs of 80 to 90% areawide. Did opt to again undercut NBM highs particularly with northward extent to be closer aligned to ensemble means, though will note there could be a fairly tight gradient locally as the warm sector attempts to lift along the I-57 corridor. Nevertheless, will advertise highs in the upper 50s near the Wisconsin state line to the mid 60s south of I-80.
Finally, am not seeing any obvious warning signs for severe thunderstorms locally with the cyclone, but it's still a bit to early to say for sure given the aforementioned variance in phasing within the ensemble envelope.

Friday Onward:

As the surface low pulls away (and deepens toward 990 mb in southern Ontario), the arrival of a strong (nearly 1040 mb)
surface high pressure system into the central Plains will set the stage for an impressive pressure gradient across the Great Lakes. Accordingly, do expect a windy day on Friday with early BUFKIT mixing profiles supporting frequent gusts of 30 to 40 mph. Such strong winds will facilitate aggressive low-level cold air advection in the wake of the cyclone with mean 850mb temperatures plummeting 10 to 15 degrees C in 24 hours (to near or below 0C). Taken together, Friday will feel every bit like October with highs in the 50s, blustery northwest winds, and showers of leaves (not water) flying through the air. With that said, a notable temperature difference between Lake Michigan water and the fall airmass will support lake effect rain showers mainly east of Gary.

There remains ensemble agreement that the surface high will slide directly over the Great Lakes Friday night into Saturday morning setting the stage for ideal radiational cooling and the coldest night of the autumn season so far. Assuming no major changes in forecast guidance, would expect areas of frost and even locally freezing temperatures across the region right in line with climatology (the first freezing temperatures away from Lake Michigan typically occur in the October 11 to 20 timeframe).

Thereafter, ensemble guidance advertises the surface high stalling over the Atlantic Seaboard and the northward-shift of the dominant upper-level jet into Canada supporting gradually rising temperatures into next week.

Borchardt

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
Issued at 135 PM CDT Tue Oct 13 2026

Key Messages:

- Showers and scattered thunderstorms are likely to affect the terminals tonight.

- A period of MVFR ceilings is likely tomorrow.

Strengthening warm air advection/isentropic ascent will lead to an increase in shower and thunderstorm coverage across the area this evening. Uncertainty remains regarding the exact onset time of the shower and thunderstorm activity and how long it will persist near any one TAF site. In general, the chances for lightning are greater at the Chicago metro terminals than they are at RFD, where the 18Z TAF was reconfigured to contain two PROB30 groups with TSRA for two potential discrete waves of showers and storms. At the Chicago metro terminals, it's possible that this activity may also end up breaking down into one or two distinct waves, but it also remains possible that there could just be one longer, drawn-out period with showers and storms in the vicinity of the terminals instead. Opted to maintain an extended period of TSRA/VCTS in the TAFs there for that reason, and will let this timing be refined as model and observational trends become clearer. There is also some chance for scattered showers to persist well into the morning at/near the Chicago metro terminals tomorrow if tonight's convective footprint ends up being smaller than expected. However, this is presently not the most likely outcome, so the TAFs do not contain any formal precipitation mentions beyond 11Z at this time.

MVFR stratus is expected to develop over the area sometime late tonight or tomorrow morning. Persistent northeasterly onshore flow will likely maintain this stratus deck through the remainder of this TAF period, though there is some chance that cloud bases could lift above 3000 ft AGL prior to the end of the TAF period, especially at RFD. If this stratus deck grows thick enough, then couldn't rule out patchy drizzle or a fine mist developing somewhere, but the odds of this occurring at any particular TAF site remain fairly low (10-15% chance) at this time.

Ogorek

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