textproduct: Chicago

KEY MESSAGES

- Occasional sprinkles/light rain showers are expected in the area this morning.

- Near to slightly below normal temperatures are forecasted over the next several days.

- The next chance for a widespread, wetting rainfall won't come until at least the middle of next week.

DISCUSSION

Issued at 215 AM CDT Fri Sep 25 2026

A pair of upper-level shortwaves is evident over the Midwest in GOES water vapor imagery loops early this morning, with one of these waves drifting eastward across northern Wisconsin and the other lifting northeastward into Iowa from the central Plains. Near and between those two shortwaves, a thick mid-upper-level cloud deck has supported a smattering of 20-40 dbZ radar reflectivity returns on regional radar mosaics (including near and over our forecast area), though a lot of these returns have just been virga with dry low-mid-level air thwarting the attempts of descending hydrometeors to reach the ground. While a modest easterly feed of dry low-mid-level air spurred by expansive high pressure to our northeast will continue to make it difficult for a meaningful amount of top-down saturation to occur amidst less-than-stellar synoptic-scale forcing for ascent, the expectation is that enough saturation of the dry low-level air should occur for occasional sprinkles to be observed in our forecast area this morning. Could envision some isolated instances of measurable rainfall (no more than a few hundredths of an inch) occurring as well, so did continue to carry slight chance PoPs in the forecast grids this morning -- primarily focused over the northern half of our CWA. Slightly below normal high temperatures in the mid-upper 60s are otherwise expected today without much additional fanfare.

Similar to slightly warmer high temperatures are then forecasted through the weekend and into early next week amidst a mix of sunshine and clouds and no real air mass changes of note as a Rex block develops over the eastern CONUS. Saturday night into Sunday morning, another disturbance will attempt to make inroads into the Great Lakes from the central Plains. However, its northeastward progress will be halted as it runs into the aforementioned region of high pressure within the Rex block, and similar to today, the continuing associated feed of dry low- mid- level air will make it difficult for any accompanying rainfall to penetrate well into our forecast area. There may nevertheless still be a period of decaying showers or sprinkles during this time frame (primarily in our western counties), but otherwise, dry conditions are favored to prevail over the weekend through at least Tuesday morning.

By mid-week next week, the eastern CONUS Rex block will have broken down, allowing for a more progressive weather pattern to take shape. Exactly how things will play out here mid-late next week remains quite uncertain at this time, largely owing to the expectation that an upper-level trough will likely become cut- off from the polar jet stream and then undergo a complex interaction with the remnants of Pacific Hurricane Polo over the Desert Southwest midweek. Additional disturbances still embedded in the jet stream may then potentially interact with whatever comes of this phasing attempt between these two features as they lift northeastward, which further muddles the picture here for the end of September and the start of October. Despite this, there is fairly strong ensemble support for an influx of moisture and a frontal zone coming through the region mid-late next week, so it's a fairly good bet that it will probably rain here at some point (and possibly more than once) during this time frame. Exactly when this rain will occur and how much of it we'll get is something that we won't really be able to drill down until forecast trends become clearer in the coming days.

Ogorek

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 1244 AM CDT Fri Sep 25 2026

VFR conditions are forecast through the period. Precipitation associated with a weak disturbance moving across the area early this morning is expected to remain mainly virga owing to pronounced dry air in the lower levels. Have accordingly maintained a dry forecast with this update. However, a stray shower or sprinkle can't be fully ruled out through mid morning, particularly near Rockford (< 30% chance).

Winds will remain generally easterly around 5-10 kt through the period (ESE to ENE), and at times light and variable < 5 kt during the overnight hours.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

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