textproduct: Chicago

KEY MESSAGES

- Mild temperatures (highs in the 50s) are expected today.

- Widespread light rain (>80% chance) Monday night into early Tuesday.

- Turning cold and blustery Wednesday with wind gusts > 35 mph, potentially paired with a few flurries.

- Unseasonably cold temperatures (highs in the 30s) continue on Thanksgiving and through the end of the week.

DISCUSSION

Issued at 314 AM CST Sun Nov 23 2025

Surface high pressure will foster a mostly sunny and dry day across the region as it tracks eastward across the Mid- Mississippi Valley today. With abundant sun, expect temperatures to be a bit warmer than yesterday, with readings expected to top out in the low to mid 50s. This relatively mild weather will persist through Tuesday, albeit with a chance of light rain Monday night into early Tuesday. Thereafter, a significant weather pattern shift is expected to driver our area into a much colder (winter-like) airmass for the later half of the week.

Low-level flow will turn south-southwesterly tonight into early Monday following the eastward departure of the surface high, and in response to the approaching impulse ejecting out of the Desert Southwest today. As this occurs, low-level moisture will surge northward into the area by early Monday morning, and this adds concern for the development and expansion of a very low stratus deck (IFR to LIFR) into our area for Monday. Current conditions already indicate that low stratus and fog are ongoing in the Ozarks, and several models (particularly the RAP, HRRR and NAMnest) have this area expanding northward tonight. This adds concerns for our temperature forecast for Monday. If we end up with an expansive area of low stratus, temperatures on Monday may remain nearly steady in the low to mid 40s. After collaborating with neighboring offices we have opted to cut the NBM forecast highs in the mid 50s by several degrees, going closer to 50 for highs on Monday. Admittedly, however, these readings may still be several degrees too warm.

While low-level cloud cover could be in our future for Monday, it still appears that most of the daylight hours will remain precipitation free. Light rain chances will then begin to ramp up Monday night as deeper moisture arrives with the approaching impulse shifting over the Mid-Mississippi Valley. Overall, this period of rain does not look to amount to a whole lot, with most areas likely to see less than a quarter inch before the light rain tapers off Tuesday morning.

Following quickly on the heals of this system, another quick moving northern stream impulse will quickly dig in across the western Great Lakes Tuesday night into Wednesday. As it does, surface low pressure will deepen and consolidate north of our area over the Upper Great Lakes, with an associated strong east- southeastward surging cold front expected to punch eastward across the area Tuesday night. In the wake of this frontal passage, strong cold air advection and rapid pressure rises will drive increasingly strong gusty west-northwesterly winds (possibly gusting in excess of 40 mph at times) late Tuesday night into the day on Wednesday. While not much in the way of precipitation is expected for Wednesday, some occasional flurries or intermittent light snow showers may occur with any lingering strato Cu. However, the primary weather story will be the gusty winds with a quick turn towards a much colder, winter-like airmass for the second half of the week, including on Thanksgiving Day. Expect high temperatures to only be in the low to middle 30s with wind chills in the teens and 20s.

Beyond Thanksgiving, signs continue to point to a turn towards a much more active weather pattern across the central CONUS this weekend going into the first week of December. Overall, the larger scale pattern across North America continues to favor upper troughing setting up across the western CONUS and upper ridging across the southeastern CONUS during this period. The presence of greatly enhanced southwesterly mid and upper level flow into the lower Great Lakes in such a pattern is notorious for steering numerous impulses across our region. Accordingly, some periods of active weather, with rain and/or snow is possible as we head into next weekend. It is important to note, however, that as is typical, while the pattern looks increasingly active, the finer scale details this far out remain largely unclear and will need to be ironed out in the coming days. Nevertheless, this period will be monitored closely for potentially impactful weather systems across the central CONUS that could impact holiday travel. Stay tuned.

KJB

AVIATION /12Z TAFS THROUGH 18Z MONDAY/

Issued at 533 AM CST Sun Nov 23 2025

Main Concern:

- Potential for low CIGs and some VSBY reduction Monday morning.

Quiet VFR flying conditions will prevail until early Monday morning. A large bank of low stratus (IFR to LIFR CIGs) and fog that resides across the Mid South and Ozarks early this morning will then probably be drawn northward by strengthening southwest flow aloft later tonight into Monday morning.

Since not all guidance has picked up yet on this potential or likelihood of lower flight categories on Monday, started out with prevailing low MVFR CIGs and a hint at lower IFR in the ORD and MDW TAFs. Forecast soundings from the guidance believed to have a better handle on trends suggest that LIFR CIGs are a distinct possibility. The strength of the low-level winds just above the surface cast uncertainty on more noteworthy VSBY reductions in fog, so indicated 6SM BR for now.

West-northwest winds of 10 kt or less today will shift to southwest towards sunset and then light southerly overnight, followed by southerly speeds increasing to near/around 10 kt on Monday morning.

Castro

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 10 AM CST this morning for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.