textproduct: Chicago

KEY MESSAGES

- Rain will develop northeast across the area this afternoon.

- A period of thunderstorms are favored after dark this evening and there is a low chance (5% chance or so) for severe weather in the form of damaging winds along and east of I-55 from 6 PM to 10 PM this evening. Some locally heavy rainfall may also accompany these storms this evening.

- Another storm system will deliver a round of snow, strong winds, and falling temperatures Saturday and Saturday night.

DISCUSSION

Issued at 328 AM CST Thu Jan 8 2026

Through Tonight:

Our main weather maker for later today into tonight is the mid- level shortwave (and its accompanying upper-level speed max) currently noted in the water vapor imagery shifting across eastern New Mexico. This feature will drive a low 990s mb surface low northeastward from eastern Kansas later this morning out across eastern IA into early this evening. As it does, increasingly lower level southerly winds will increase today and transport an unseasonable high theta-e airmass northward across IL and IN through the afternoon. This will undoubtedly foster warming temperatures into the 50s this afternoon. However, even warmer temperatures are expected after dark this evening following the northward passage of the surface warm front as the surface low shifts northward from eastern IA towards WI. Gusty south-southwest winds (gusts up to 35 mph) in the warm sector will result in temperatures peaking not too far from the record highs this time of year (readings well into the 50s to near 60) late this evening, before temperatures begin to cool later tonight as the cold front quickly shifts into the area.

While it will be unseasonably mild today, the increasing warm and moist advection is expected to drive a blossoming area of rain northeastward into the area through this afternoon. The threat of thunderstorms with this initial period rain will remain low through the afternoon. However, as we head into this evening atmospheric dynamics are expected to quickly ramp-up overhead with the approaching warm front. Specifically, forecast guidance suggests that as the exit region of a 80+ kt upper jet noses into the area this evening a strong low-level mass response will drive up to 70 kt of southerly low-level flow around 850 mb. This will certainly set the stage for a rather impressive kinematic environment that will be more than supportive for potential strong to severe thunderstorms this evening.

Unfortunately, as is typical with cold season severe weather setups the kinematics are often very impressive while the thermodynamics are rather modest. This evening looks to be no different, as a modest steepening of the low-to-mid level lapse rates looks to support a few hundred j/kg of MUCAPE. Nevertheless, with surface dewpoints approaching the upper 50s, particularly along and southeast of I-55, within a strongly sheared and dynamic environment, you can never discount the threat of severe thunderstorms during the cold season. Current thinking is that the primary threat for any severe thunderstorms will be this evening between 6 and 10 pm for areas roughly along and southeast of I-55. The main severe threat looks to be damaging wind gusts, in line with the 1 out of 5 threat highlighted in the latest SPC day one outlook.

Also, in addition to the severe threat, the near record precipitable water values (just in excess of 1"), along with deep warm cloud depths (up to near 10,000 ft) will be supportive of instances of heavy rainfall within these storms this evening. While a significant flash flood risk in not anticipated, the prospects for some locally heavy rainfall along narrow west-southwest to east-northeast corridors across eastern IL into northwestern IL this evening could result in some localized nuisance flooding issues.

The threat of storms and heavy rain will come to an end from west-to-east after midnight tonight. Gusty west-northwest winds will develop late tonight into Friday morning along the back side of this exiting area of low pressure.

KJB

Friday through Wednesday:

Early Friday, the last of the rain from Thursday's storm system is expected to still be working out of the area, mainly in our northern and eastern CWA. The area should be mostly dry by mid- late morning, but there still exists a signal for a period of drizzle and low stratus into the afternoon. Cold advection left behind from the storm will not allow temperatures to warm much and most of Friday is expected in the 40s until we cool into the 30s during the evening.

Friday evening, the gap will begin to close between two upstream waves, one scooting across the southwestern US border and the other dropping into the northern Plains from Canada. The two will phase into one sprawling upper low directly atop the Midwest on Saturday, and the result will be our next shot at seeing accumulating snowfall. A good deal of uncertainty still looms around this rapidly evolving system, including in P-types and snow coverage, which of course immediately translates to uncertainty regarding snow totals. Precip chances arrive as early as late Friday night, but a number of models hold off on precip until after the start of Saturday, if not later even. The best shot at any densely scattered to widespread coverage will be during the morning and afternoon. P-types during this time are a big question with forecast soundings across available guidance on the fence of a profile supportive of rain and one of snow during the earlier part of Saturday. If anything falls on the CWA prior to sunrise on Saturday, soundings favor rain. There's a good chance that parts of the area see a couple hour period of a wintry mix, but all snow is favored by mid-afternoon or so.

Coverage becomes especially uncertain from the evening onward and isolated to scattered snow showers will be possible just about anywhere in the CWA through the night. The ingredients for heavy banded snow are not quite there, but some forecast soundings offer a signal for some localized fingers of relatively higher snow rates, particularly during the evening right as the center of the upper low swings through the vicinity. This signal entails some potentially steeper low level lapse rates, an accelerating low level wind field, and transient vorticity around the passing upper low. Should we see something like this develop, it could lead to localized streaks of slightly higher totals but would not appear to have significant influences on accumulations. A chance for additional snow showers Sunday morning will favor areas around the lake as a backdoor baroclinic zone drops south across the lake during the morning. High pressure will inch in behind and should put an end to snow chances by the end of the morning, likely sooner for most.

As far as totals go, ensemble exceedance probs are highest across our northern CWA, but individual deterministic camps offer a wide variety of solutions for not only snow amounts but how they'll be distributed across the area. Even the spread in totals within individual ensembles is larger than you'd like to see. The 25th and 75th percentiles from the LREF (a GEFS/ENS/GEPS mashup) across our northern CWA are a trace and over three inches, respectively. So while there is confidence that this won't be a terribly impactful event, this does make it difficult to gauge the magnitude of impacts around the area, especially when you mix in considerations for blowing and drifting snow with support for up to 30 to 35 mph gusts Saturday evening and night (more specifically on winds in a bit.) Lingering wetness on roads may limit this concern to an extent. The updated forecast calls for less than an inch around a majority of the area with as high as 2 to 3 inches along the WI state line. At least minor impacts to travel appear probable mainly across northern portions of the area, but even light snow showers during the evening and night may make for hairy driving conditions due to potentially reduced visibilities in blowing snow.

In other weekend news, temperatures during the day on Saturday are forecast in the 30s to near 40. Continued cold advection will bring highs down to around or below freezing on Sunday. After the cold advection first takes off Saturday evening, the boundary layer will open up to some strong low level flow circling the stacked upper low. Gusts to around 25 to 30 mph are strongly favored during the evening and overnight. Most guidance insists the strongest winds will come Sunday morning and afternoon when the deterministic Euro has consistently been resolving widespread 35 to 40 mph gusts run to run. This not only leads to some blowing snow concerns as previously mentioned, but will also make conditions feel even cooler this weekend. Wind chills are forecast in the 20s for the better part of Saturday, possibly dropping into the single digits Saturday night, and in the teens during the day on Sunday.

Rather quiet weather is then expected for early next week. We'll trend toward seasonably mild temperatures again before another storm system looks to drop into the region around Wednesday reeling in cooler air from the north and providing additional opportunities for rain and snow. Will get into those details later as more come into focus.

Doom

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/

Issued at 555 AM CST Thu Jan 8 2026

Key messages for the 12Z TAF period:

* LLWS through mid-morning

* A system of gusty showers this afternoon and evening with the potential for embedded heavy rain, thunder, and strong winds

* IFR late this afternoon and evening associated with the storm system, with MVFR continuing through the end of the period

* A period of LLWS this afternoon

* Gusty SW to NW winds tonight into Friday

A system of rain showers will work over the airfields mid-late afternoon and categories are expected to drop from VFR to IFR in the span of an hour or two after the onset of rain. During the early-mid evening at the Chicagoland sites, there exists a potential for pockets of moderate to heavy rain, maybe a couple of lightning strikes, and strong to even marginally damaging wind gusts. After mid-evening, scattered showers and MVFR BR will linger into the overnight hours. Cigs are expected to improve to MVFR shortly after 06Z and remain as such through the end of Friday morning.

Meanwhile, we're starting the day with southerly winds (favoring SSE) below to occasionally near 10 kt. Our radar has been sampling 40 to 45 kt of flow at 2kft AGL, so maintained LLWS in the TAFs through mid-morning. Expect SSE after mid- morning when gusts to near 20 kt will kick in. They'll increase to 20 to 25 kt for the afternoon with the aforementioned potential for locally stronger winds near showers and storms. LLWS is also anticipated during the late afternoon and evening with upwards of 55 kt of southerly flow at 2kft AGL. Regular gusts to 25 to 30+ kt are then expected for the late evening through Friday morning, with direction veering through the night from SW to NW.

Doom

CLIMATE

Issued at 543 PM CST Wed Jan 7 2026

Record warmth is forecast for Rockford and near record warmth for Chicago on Thursday, January 8 and Friday, January 9. The high temperature will likely occur around midnight between both dates.

The record high and record warm low temperatures for both Rockford and Chicago are included below:

Record Highs Record Warm Lows

January 8 January 9 January 8 January 9

Rockford: 55F (1965) 56F (2002) 36F (2008) 35F (2000)

Chicago: 63F (1965) 60F (1880) 45F (1876) 45F (1939)

NWS Chicago

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory from 3 PM this afternoon to 6 AM CST Friday for the IL and IN nearshore waters.