textproduct: Chicago

KEY MESSAGES

- Quick shot of snow possible late tonight over far NE IL and NW IN.

- Milder temperatures expected for much of the upcoming work week.

DISCUSSION

Issued at 229 PM CST Sat Feb 7 2026

Mid-level cloud cover will continue to increase across the area into this evening in association with our next quickly approaching low amplitude shortwave impulse riding the northwest flow into the region tonight. While much of the area will see cloud cover around tonight, we do continue to monitor the potential for a quick hit of light accumulating snow late tonight across a small portion of the area. It is important to note that most areas will not see any snow as a result of this impulse tonight, owing to the very dry low-level airmass in place. Instead, we are watching areas generally along a narrow north-northwest to south- southeast oriented corridor that extends from southeastern WI and far northeastern IL (especially in close proximity to Lake Michigan) southeastward into parts of northwestern IN. Forecast guidance continues to insist that top-down saturation will occur in this corridor and support a short period (2-4 hours) of snow later tonight. This certainly seems plausible since this is also the general region in which a transient band of frontogenesis is favored to develop and support some enhanced forced ascent. We have thus continued to confine chance to low end likely POPs (30-60% chance) in this general area overnight. The short duration of snow should result in light amounts of a coating to perhaps locally up to an inch.

A large scale weather pattern change is slated to take place into the first portion of the upcoming work week. This will occur as the persistent high amplitude ridging over western North America begins to deamplify and transition the upper-level pattern across most of the country into a more quasi-zonal flow pattern (west-to-east) for a period next week. Overall, this will set the stage for a milder airmass across our region this week as the very cold airmass remains north of the area.

The threat of precipitation also looks to remain low (<20%) across our area through at least mid-week, owing to expectation of weather systems tracking well north and south of our area. Our mildest period this week looks to be Monday into Tuesday, when high temperatures look to tag 40 degrees in most areas. A weak cold front is expected to drop southward across the area on Tuesday. This should bring cooler (highs in the 30s) more seasonable weather back into the region for the remainder of the week.

There remains a lot of uncertainty with a potential late week system. Didn't make any changes to the pops offered up by the NBM, but there continues to be some signal for precipitation potential late in the week, particularly from EPS members.

KJB

AVIATION /00Z TAFS THROUGH 06Z MONDAY/

Issued at 532 PM CST Sat Feb 7 2026

Key Messages for the 00Z TAFs"

- Period of light snow and MVFR conditions possible for Chicago terminals overnight.

Surface high pressure ridge has drifted east across the area this afternoon, with winds in the process of turning light east-southeasterly. Weak lake breeze has pushed through ORD/MDW making for a slightly more easterly direction across the metro. Off to our west, an area of surface low pressure along the South Dakota/Nebraska border will propagate southeast across the lower Missouri Valley tonight into Sunday, which will maintain modest southeast winds around 10 kt across the terminals through the end of the TAF period.

The surface low is associated with a pair of upper-level disturbances which will track southeast across the area through Sunday morning. Increasing mid-high level VFR clouds are already spilling across the area early this evening, with associated radar returns from MN/WI into northwest IL. The low level air mass is quite dry however (surface dew points in the single digits either side of 0F), and these radar returns currently indicate snow above 100-120 kft sublimating before reaching the surface. Various model guidance continues to indicate that top- down saturation may eventually allow light snow to reach the ground across southeast WI and far northeast IL. Have thus maintained a prob30 mention for light snow and MVFR vis for the Chicago terminals (have maintained dry forecast at RFD) in the 04-10Z period for this potential. If saturation is more complete, can't rule out some IFR conditions along with some accumulations of less than an inch. The threat does look to end prior to 12Z.

Dry, VFR conditions are then expected through the remainder of the forecast period.

Ratzer

LOT WATCHES/WARNINGS/ADVISORIES

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