textproduct: Chicago

KEY MESSAGES

- Turning breezy tonight with scattered showers and a low chance (20%) of thunderstorms.

- Elevated fire danger Wednesday with westerly winds gusting to 30-40 mph.

- Additional rain chances Thursday night/Friday morning and possible rain/snow chances Friday night/Saturday.

DISCUSSION

Issued at 326 AM CST Tue Feb 17 2026

It will not be quite as warm today as it was on Monday, owing to more mid and high level cloud cover. However, with temperatures away from the northeastern IL Lake Michigan shore expected to climb well into the 50s to near 60, it will be another unseasonably mild day. Cooler conditions are anticipated across far northeastern IL along the shore from Chicago northward due to an onshore southeasterly wind through the day. Accordingly, temperatures here will be held down in the 40s.

Forecast attention into tonight turns towards the strong southwesterly upper-level jet developing onshore across the Desert Southwest, along the southern periphery of a west coast upper trough. This active west-southwesterly jet streak will expand eastward and drive a couple of storm systems across the central portion of the country through the end of the week. The first, is now taking shape across the northern High Plains as an elongated area of surface low pressure in advance of an approaching mid-level impulse over northern UT. This expansive storm system will quickly occlude tonight into Wednesday morning as it shifts eastward into the upper Midwest. Then, following quickly on its heels, another significant impulse ejecting out of the southwestern CONUS trough midweek will drive another storm system into the western Great Lakes sometime late Thursday into Friday.

Southerly winds will ramp-up and become gusty (30-35 mph) this evening and tonight, owing to the a strengthen surface pressure gradient in advance of the expansive sub-990 mb surface low shifting into the Upper Midwest. The associated warm/moist air advection pattern will also support developing showers as the column moistens this evening. This is not looking to be a big rain event for the area, as most areas will see less than a tenth of an inch of precipitation. Nevertheless, the best chances (60-70%) for these showers will be across northeastern IL into northwestern IN in the 9 PM to 4 am timeframe. Steepening mid-level lapse rates may also support a few embedded non-severe thunderstorms with this activity.

Conditions dry out considerably and become windy on Wednesday following an eastward surging frontal boundary/quai-dry line. Dewpoints in the wake of this boundary are likely to fall into the 20s as surface temperatures efficiently warm into the mid 60s during peak afternoon mixing. This should equate in afternoon minimum RH percent values falling into the low 20s Wednesday afternoon, particularly along and west of the Fox Valley and interstate 55 in northern IL. These very dry conditions in combination with westerly wind gusts of 30-40 mph during the day will result in near Red Flag conditions. The main question is how dry will the fuels be following any potential light rain tonight. Due to the uncertainties in the fuel moisture we have opted to hold off on any type of Fire Weather Watch at this time. Nevertheless, we will continue to message Wednesday as a day to postpone outdoor burning.

Ensemble guidance continues to support another potent storm system tracking eastward across the central part of the country, then northeastward into the western Great Lakes late Thursday into Friday. There remains uncertainty with this system, but chances continue to increase for another period of windy and stormy weather late Thursday into Friday. We will also have to keep a close eye on the threat of severe storms into parts of the area late Thursday as the surface low, and its accompanying warm front lift northward across IL. Conditions will then trend colder in the wake of this system for the weekend into early next week. This will result in a return to temperatures more typical of mid to late February (highs in the 30s and lows in the teens and 20s).

KJB

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 530 AM CST Tue Feb 17 2026

Key Aviation Messages for the current TAF period:

- Gusty southeast winds late afternoon/tonight.

- Periods of showers move in this evening through the overnight. MVFR cigs/vis expected with some IFR possible.

- Gusty winds turn to the southwest Wednesday morning after the rain/drizzle ends.

Higher clouds over the airspace has helped prevent fog developing this morning. Winds are light and out of the southeast. Expected winds to increase through the late morning afternoon ahead of the next system. Wind gusts will develop late in the afternoon to 25 knots with gusts to 30 knots possible with the rain tonight.

A weak system is expected to pass over the area providing periods of rain tonight. Rain totals look minimal, but it will be enough to wet runways. Cigs are expected to drop to MVFR levels however IFR cigs/vis are possible during any stronger shower. There is a chance for thunder with this system, but as the probability remains less than 30 percent, it was kept out of the TAF still.

Lower confidence in MVFR cigs and drizzle lingering in the wake of the main system into Wednesday morning. However, conditions are expected to improve dramatically back to dry and VFR after 12Z. Winds will slowly back to the southwest. Models are suggesting there might be a lull in the wind gust Wednesday morning, it was for too short of a period to add to the current TAF. There was higher confidence in southwesterly wind gusts strengthening late tomorrow morning. It is possible that the current gusts will need to be increased as strongest gusts over 30 knots are expected after 18Z.

DK

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory from midnight tonight to 6 PM CST Wednesday for the IL and IN nearshore waters.