textproduct: Chicago

KEY MESSAGES

- Windy and unseasonably warm today.

- Showers likely later today and tonight, with a good soaking rainfall expected over much of the area before tapering off Wednesday morning.

- A return to more seasonable temperatures expected late this week into the upcoming weekend.

DISCUSSION

Issued at 225 AM CST Tue Nov 3 2026

Early morning surface analysis depicts a pair of low pressure systems across the Plains and upper Midwest, one across northeast MN and the other across south-central KS. The southern low is forecast to lift northeast into eastern IA through this evening, before deepening to around 997 mb and continuing into western WI by early Wednesday. This deepening is in response to a strong mid-level short wave trough rotating around the base of the larger scale upper trough across the central CONUS. Eventually, the mid-level closed low is progged to become vertically stacked above the occluding surface cyclone and drift east-northeast across the northern Great Lakes region Wednesday night into Thursday.

In the near term, a broad region of enhanced low-level southerly flow was in place east of the low across the Midwest. Warm/moist advection on south winds gusting to 20-25 mph continue to produce an extensive low-stratus deck and drizzle at this hour, in addition to unseasonably warm overnight temps in the low-60s. Current obs trends indicate cloud bases lifting from south to north, which will end the drizzle early this morning. The tight surface pressure gradient will continue to support strong/gusty southerly winds across the area today into tonight, with gusts 35-40 mph especially later this morning through this afternoon/early evening. Depending on how deeply the boundary layer can mix, 40+ mph gusts are possible especially across our southern/eastern counties where cloud cover looks to be thinner allowing warmer low-mid 70s temps. Farther north/northwest, more cloud cover and increasing shower chances may limit temps to the mid-upper 60s.

Large scale forcing will begin to increase later this morning/today however, as the strong Plains short wave lifts northeast into the region. Rain/showers and some embedded thunderstorms (currently evident across MO/southern IA) will spread into the forecast area from the southwest later this morning into this afternoon. This strongest forcing continues to appear to be focused over the area this evening and overnight, ahead of the slightly negatively-tilted wave and approaching surface cold front. The combination of this forcing, deep moisture (PWATs approaching 1.70" or nearly 300% of normal) and north-south mid-level frontogenetic banding, will likely support fairly widespread rain amounts in excess of a half inch, with some locally higher amounts especially across the western half of the forecast area.

Rainfall will taper off from west to east Wednesday morning behind the cold front, though scattered showers may linger at times into the end of the week as the upper trough drifts slowly over the area. In fact, the upper trough is progged to be slow to exit to the east through the end of the week, with some guidance (notably the EC/ECE) keeping the remnant upper level low across the Great Lakes region through Friday. Eventually mid-level short wave ridging should develop behind the departing trough, at least temporarily, with current ensembles indicating dry weather from late Friday into Saturday. Additional shortwaves rippling into the region in northwest flow aloft later in the weekend may bring back some scattered shower chances in the Sunday-Monday timeframe.

Temperature-wise, after well-above average warmth today, readings will trend cooler behind the cold front on Wednesday with highs in the upper 50s/low 60s. Daytime highs in the 50s and lows in the 30s/40s are expected Thursday through the weekend, which are around our averages for this time of year.

Ratzer

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 600 AM CST Tue Nov 3 2026

Main Concerns:

- Strong/gusty southerly winds today-tonight, but especially mid to late morning through early to mid afternoon

- Showers initially in RFD area and points west later this morning will gradually expand eastward into the Chicago metro, with showers then continuing Wednesday morning, ending by midday

- Lower CIGs will remain primarily confined to RFD area and points north/west today, and then return to the Chicago metro terminals tonight into Wednesday morning

A slow moving low pressure system will affect flying conditions across the ZAU and C90 air spaces today through Wednesday morning. With primarily VFR conditions at the Chicago metro terminals today, the main item of note is strong southerly winds (180-200 deg) expected to peak from about 15z until 21z (earlier decrease with westward extent). During this time, forecast soundings suggest gusts to around 30 kt, and a plausible upside potential to the mid-upper 30s kt range.

Prevailing rain showers are expected several hours earlier at RFD than at the IL Chicago metro terminals, with an even later start at/near GYY. Scattered SHRA may affect the IL Chicago metro terminals at times this afternoon. Later today into tonight, there's a 15-20% chance for embedded TS, mainly at RFD, though confidence remains too low for any mention. During the most widespread SHRA (overnight-early to mid Wed AM at the Chicago metro terminals), at least occasional MVFR VSBY is favored.

Winds (gusts to 20-25 kt) will likely shift to south-southeast tonight and then back to southerly Wednesday morning, followed by a wind shift to southwest mid to late morning with the cold frontal passage.

Castro

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 6 AM CST Wednesday for the IL nearshore waters.

Small Craft Advisory from 9 AM this morning to 6 AM CST Wednesday for the IN nearshore waters.