textproduct: Chicago

KEY MESSAGES

- Seasonable temperatures are expected the rest of the week, though not a lot of sunshine.

DISCUSSION

Issued at 245 AM CST Wed Nov 19 2025

Stratus deck currently blankets much of Illinois, Indiana, Iowa, and adjacent portions of southern Wisconsin and lower Michigan. This stratus is trapped beneath a sharp inversion seen around 900mb on recent ACARs flights out of MDW. Recent GOES nighttime microphysics RGB imagery does show some erosion of the stratus across southeast WI and southern Lake Michigan. Tuesday evening sounding from KAPX showed a very dry low level air mass in place across northern lower Michigan and northeasterly flow near/below the inversion is likely advecting drier air southwestward and helping chip away at the stratus.

Low confidence at how far any clearing from this erosion of the stratus deck will get into northeast IL/northwest IN this morning before low level flow veers more southeasterly and likely results in a sloshing back northwest of the stratus. For now, leaned toward mainly cloudy conditions in the grids for today and only show a few degree temp recovery for highs because of that. Should skies clear more than expected over northeast IL, then temps would likely need to be nudged upward a few degrees.

If there is any clearing early today, that should give way to a return of stratus this afternoon and likely hanging on through Wednesday night as light southerly flow and lingering inversion keep stratus locked in. Southerly flow should pick up a bit Thursday and that may be enough to push the stratus deck north of the area, but confidence in that is quite low. Even if stratus were to move out Thursday, extensive mid-high level cloudiness would likely keep skies fairly cloudy as moisture streams northeastward ahead of a southern stream trough.

NBM remains on the warmer end of the spectrum with high temps Thursday. If the stratus clears out and especially if there are breaks in the mid-high level cloudiness, then it is possible that we could see highs well into the 50s, but seems more likely that cloud cover should keep it cooler. Nudged forecast highs down a bit over northeastern CWA Thursday, but could definitely see forecast highs needing further lowering as confidence increases in skies remaining cloudy.

Still looking like a split flow regime will be the rule through the upcoming weekend with a deep longwave southern stream trough over the southwestern U.S. and with the northern stream buckling south into the Great Lakes. It's looking increasingly likely that confluent flow between northern stream and southern stream should lead to a dampening of any energy emanating from the western southern stream trough and attempting to move east across into the central/eastern U.S. In addition to dampening any shortwaves into the confluent flow, the west-northwesterly flow in the northern stream will probably keep meaningful rain chances mostly suppressed to the south of our CWA.

The time lagged nature of the NBM plus a few rogue ensemble members continue to result in pops much of the Thursday- Saturday time frame. In collaboration with neighboring offices, pops were removed Thursday and lowered some Friday into Saturday. As it looks now, areas of north of I-80 may not see much, if any, rain late this week and over the weekend. South of I-80, especially well south into central Illinois, stands the best chances for seeing any rain and even there chances are dwindling by the day.

Seasonable temperatures are expected into the weekend with probably a tendency toward above average temps for the first half of next week.

- Izzi

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 1125 AM CST Wed Nov 19 2025

The key aviation messages are:

- Prevailing MVFR cigs likely through the TAF period

- Potential for periods of BR and/or -DZ, greatest INVOF RFD, but could extend east to the Chicago area sites tonight into Thursday morning

Widespread MVFR stratus appears likely to remain in place through the TAF period. Some vsby restrictions due to BR and or some light -DZ are possible at RFD later this afternoon. The main signal for -DZ/BR is later this evening, overnight, and into early Thursday morning. Have introduced a TEMPO group for IFR cigs and vsbys at RFD to cover the period of greatest signal for flight category reductions, but it's conceivable IFR conditions extend beyond what's advertised in the current TAF.

Confidence in IFR remains too low at this time to justify an inclusion at the Chicago-area terminals at this time. With moisture expected to increase through the day on Thursday, vsbys may end up prevailing in the 5-7 sm range into the afternoon.

Light/variable to southeasterly winds will become southerly and eventually southwesterly late tonight.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.