textproduct: Chicago

KEY MESSAGES

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

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

DISCUSSION

Issued at 228 AM CST Sat Feb 7 2026

After our mildest temperature in nearly 3 weeks on Friday, northerly winds early this morning continue to usher in colder air. Some lake effect flurries and a couple of isolated light snow showers are streaming inland into NW Indiana early this morning. Low inversion heights have been a big limiting factor in more robust lake effect snow and with inversion heights progged to continue to lower this morning, lake effect threat should end later this morning. Not expecting any accumulations.

After a mainly sunny day, look for high and eventually mid level cloudiness to stream into the area toward, and especially after, sunset this evening. This cloudiness is in association with a low amplitude shortwave trough riding the northwest flow through the region tonight. Look for strengthening isentropic ascent tonight in advance of this wave as low and mid level flow back on the 280-295K theta surfaces. Low level air mass will be quite dry, so it will be a race to see if the virga can break through the dry low levels before strongest isentropic ascent shifts east of the area. There has been a westward trend in guidance in where the breach of the low level dry air will take place, with most guidance now suggesting a quick hit of snow over far northeast Illinois into northwest Indiana tonight. If snow does occur it looks to be brief, only lasting an hour or two, but could be enough to coat the ground. Confidence is still rather low, so held off on likely pops, but did introduce some high end chance pops over far eastern CWA tonight.

Large scale pattern change is still progged to take place during the upcoming work. The persistent high amplitude ridging over western North America is progged to break down, and be replaced by a long wave trough. Downstream ridging over central and eastern U.S. looks to be muted by lingering, persistent troughing over New England. This will result in a mainly zonal flow pattern which should keep the very cold air to our north and east, with a modified Pacific air mass across much of the central U.S. into the Midwest next week.

Guidance has continued the trend from the 12z guidance of keeping a shortwave Tuesday south of our area. In this scenario, we'd likely remain dry, but a weak cold front moving across the area also looks to keep temps in check. NBM temps are likely too warm Tuesday and would expected subsequent runs to trend a bit cooler, but confidence wasn't high enough to lower temps or remove the slight chance pops just yet.

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 is a significant contingent of EPS and GEFS members that would keep us dry through the middle-end of the upcoming work week.

- Izzi

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 551 AM CST Sat Feb 7 2026

Forecast concern for the terminals...

- Northwest winds this morning becoming easterly this afternoon.

- 30-40% chance for a period of snow showers tonight in far northeast IL and northwest IN which could result in reduced visibilities and some accumulations.

A surface high continues to settle into the Great Lakes this morning which will generally maintain VFR conditions through the TAF period. The exception however will in northwest IN where some lake effect clouds will continue to stream inland resulting in 2500-3500 ft ceilings through the morning before clouds scatter out by early afternoon. While wind speeds will generally be light around 5-10 kts, directions will become more easterly towards midday before turning southeasterly by this evening where they will remain for the rest of the TAF period.

Heading into tonight, a shortwave trough is expected to pivot into the Great Lakes and interact with some mid-level moisture which should generate snow aloft. That said, the lower atmosphere is forecast to be rather dry which may keep the bulk of the snow aloft as virga and/or flurries. However, confidence is starting to increase (30-40% chance) that the forcing may be able to generate sufficient snow aloft to saturate the lower atmosphere and lead to a period of snow showers overnight across far northeast IL and northwest IN. If this saturation does occur as guidance suggests then a 2-3 hour period of snow showers could materialize around midnight and result in some reduced visibilities (possibly as low as 2-3 miles) and a dusting to half inch of accumulation. Given some lingering uncertainty in snow coverage and intensity have opted to introduce PROB30s for the Chicago area terminals (ORD, MDW, GYY, and DPA) for this potential where low-level moisture is forecast to be greatest.

Yack

LOT WATCHES/WARNINGS/ADVISORIES

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