textproduct: Chicago

KEY MESSAGES

- Lake effect rain showers will continue into the day Saturday before ending Saturday afternoon. Showers may mix with or briefly change to wet snow this evening in spots, but no accumulations are expected.

- Seasonably cool temperatures are expected through the weekend with a gradual warming trend back to above average by the middle and end of next week.

DISCUSSION

Issued at 123 PM CST Fri Nov 13 2026

Single band of lake effect showers stretches down the full length of Lake Michigan early this afternoon. Showers in our area have been largely confined to northwest Indiana. After some wet snow mixed in with the rain showers this morning over portions of Lake County Indiana, precipitation has transitioned to all rain. No accumulations were reported to our office, though on webcams we did see some brief slushy accumulations appearing to be less than an inch on grassy and elevated surfaces this morning before it quickly melted.

Water vapor imagery early this afternoon depicts one last well defined shortwave trough and associated vort max over eastern WI. This trough axis will move south of the Lake by early this evening which should result in lowering inversion heights tonight and Saturday. Inversion heights this evening should remain favorable for a formidable lake effect band. High resolution guidance does suggest that this band could wobble back west into northeast IL this evening, likely in response to a bit of a mesolow developing over the lake. The weakening boundary layer flow should promote a strong land breeze this evening and give still favorable instability, certainly plausible that a meso-low could form. If a meso-low doesn't form, then lake effect should remain targeted on northwest Indiana this evening and regardless of meso-low development or no meso-low the lake effect should gradually shift eastward overnight into Saturday morning focusing more into Porter County and eventually east of our CWA Saturday.

The lowering inversion heights, less favorable stability profiles over land, and weakening onshore boundary layer flow would all suggest this lake effect band should struggle to penetrate as far inland later this evening and especially overnight into Saturday. Thermodynamic profiles would potentially support some wet snow mixing in this evening, given sufficient inland penetration, but with sfc temps likely just above freezing, even if the band were to penetrate far enough inland where the air mass would be cold enough for snow, accumulations would be unlikely. Overnight the lesser inland penetration should reduce snow chances, as too will the inversion heights which should drop below the -10C level, leaving lake effect convection lacking the ice nuclei needed for snow.

Outside of the lack effect tomorrow, the remainder of the area will become sunny. Mostly sunny skies are then expected through the first half of the upcoming work week. Temperatures this weekend will be near average (though given the unseasonable warmth of late, will likely feel pretty cool). Generally dry weather is expected for the upcoming work week with highs warming back into the 50s and possibly into the 60s by the end of the week. Normal highs are in the 40s this weekend through next week.

- Izzi

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 1127 AM CST Fri Nov 13 2026

Forecast concerns for the terminals...

- Lake effect rain showers to persist at GYY through Saturday morning, and may briefly transition to a rain/snow mix late this evening and overnight.

- 20-40% chance for some lake effect rain showers to graze MDW this afternoon and evening.

- MVFR ceilings to persist near Lake Michigan through tonight with otherwise VFR conditions elsewhere.

A band of lake effect rain showers will continue to move inland across northwest IN through Saturday morning. While recent radar trends do show parts of the band trying to drift westward towards northeast IL, it seems that most of these showers should stay near the IL-IN state line and out of ORD. That said, given the close proximity of the band to MDW have opted to toss in a TEMPO for a few hours this afternoon to cover the shower potential and the MVFR ceilings oozing inland.

Heading into tonight, the band of lake effect rain showers will continue to wobble near the IL-IN state line and may once again bring another period of showers to MDW after midnight through early Saturday morning. While some snow flakes may try to mix in at MDW, forecast soundings show temperatures should be warm enough to support mainly rain. Regardless, no snow accumulation is expected at MDW. That said, a rain/snow mix may develop at GYY where slightly colder air is forecast to reside, but again little to no accumulation is expected. Lake effect showers will gradually shift east and exit the terminals and northwest IN by the end of the TAF period.

Outside of the lake effect, expect some SCT to BKN MVFR ceilings to linger near Lake Michigan this afternoon before drifting east overnight with the aforementioned band. Otherwise, expect VFR conditions to prevail through the TAF period with breezy northwest winds gusting around 20 kts this afternoon easing to around 5-10 kts tonight through Saturday.

Yack

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 10 AM CST Saturday for the IL and IN nearshore waters.