textproduct: Chicago

KEY MESSAGES

- Dry conditions and a warming trend will occur this weekend into early next week.

- The next chance for precipitation is forecast mid-late next week and will likely be accompanied by cooler temperatures.

DISCUSSION

Issued at 213 AM CST Sat Nov 7 2026

An upper low tied to the subtropical jet stream will slowly meander across northern Mexico and Texas over the weekend and into early next week, yielding expansive, persistent ridging across the central CONUS. The polar jet stream will remain active with a series of disturbances getting shuttled eastward and southeastward across southern Canada and the northern and eastern Great Lakes during this time frame. However, the core of this jet will remain displaced far enough to our north to keep these disturbances and any associated precipitation a safe distance away from our forecast area. Thus, the net result of this weather pattern for northern Illinois and northwestern Indiana will be precipitation-free conditions and a warming trend from near-normal high temperatures today to above normal high temperatures (likely in the low-mid 60s) by Monday and Tuesday. Low temperatures will also generally trend upward from this morning's widespread freezing/near-freezing conditions, though additional near to slightly below freezing lows could be observed in some spots again Sunday morning and once more Monday morning.

Clear nocturnal skies and light/calm winds may lead to some localized patchy fog development this morning in a few locations, but this isn't expected to become a widespread issue. Interestingly, multiple pieces of forecast guidance are signaling that advection fog may drift into our area tonight/Sunday morning as modest low-level warm/moist advection in advance of a surface trough/weak cold front attempts to saturate the planetary boundary layer. An examination of HRRR, RAP, and RRFS forecast soundings suggests that there may be just enough separation between surface temperatures and the steadily rising surface dew points to have this influx of low-level moisture manifest itself as more of a low stratus deck, but at least localized visibility reductions at ground level do appear to be a distinct possibility tonight into Sunday morning -- particularly with northward and westward extent across northern Illinois.

Ensemble guidance remains in relatively good agreement on a pattern change occurring during the latter half of this upcoming week as several upper-level disturbances amalgamate to yield deep aggregate longwave troughing across the northeastern quadrant of the CONUS. This troughing will likely end up encompassing most or all of the Great Lakes region, and there has been an increasing ensemble signal for lake effect precipitation occurring in our forecast area late next week as a result. Individual shortwaves embedded within the longer wavelength troughing could also deliver a broader wave or two of synoptic precipitation to the area during the mid-late week time frame as well, though there has been less spatiotemporal consistency and overall agreement amongst Grand Ensemble members on this possibility being realized. As the composite longwave trough becomes established, a cooler air mass will also barge into the region and could end up influencing what types of precipitation are seen here late next week. Just how cold temperatures will get in our area late next week into next weekend will depend on the exact longitudinal positioning of the longwave trough axis, which is an item of relatively low confidence at this time.

Ogorek

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 545 AM CST Sat Nov 7 2026

FEW to BKN coverage of thin VFR high clouds will drift across the area today. Winds gradually increase through the morning, becoming westerly around 10 kt by midday. Winds then ease after sunset and trend southwesterly.

There is a signal for an area of low stratus or fog to develop across northeast Iowa and southwest Wisconsin tonight, if this were to occur, it would likely move across the local area late tonight into Sunday morning. For now have handled this by including a FEW005 SCT015 mention in the 8-10Z timeframe. However, if confidence increases, prevailing IFR (or lower) CIGs and/or VSBYs may become warranted with later updates.

Winds may also become increasingly gusty out of the west during the 8-10Z timeframe with gusts in the 20-25 kt range then persisting into the day on Sunday.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 9 AM CST this morning for Calumet Harbor IL to Burns Harbor IN.

Small Craft Advisory until 3 PM CST this afternoon for Burns Harbor to Michigan City IN.