textproduct: Chicago

KEY MESSAGES

- Strong westerly winds (gusts in excess of 50 mph) and much colder temperatures will define Wednesday. A few showers will occur north of Interstate 80, as well.

- Blustery and cold weather will continue through the evening hours on Thanksgiving Day.

- Impactful snow may occur this weekend, focused on Saturday. It's still too early to get into the details.

UPDATE

Issued at 752 PM CST Tue Nov 25 2025

Minor adjustments made to the going forecast this evening, mainly to speed up front and associated showers slightly, and to increase winds more quickly behind the front overnight. Overall character of forecast remains unchanged.

Deepening surface low pressure of 1001 mb was analyzed near Eau Claire, WI as of 01Z, with a sharp cold front trailing into far western IL. The front is perhaps a hair faster than earlier high-res guidance forecasts, and have updated hourly gridded forecast for a little tighter resolution in space/timing. In addition, peak wind gusts behind the front have generally been observed near 35 kts (higher farther west across central/western IA), and thus have bumped up wind speed/gusts more quickly behind the front overnight. Start time of 3 AM CST for our wind advisory still looks to be on target for the arrival of the stronger winds to our west. The cold front was just entering our western cwa as of this writing, and should push east across the Chicago metro through 10 PM or so based on current progress. An area of showers along/just ahead of the front will also shift east with the boundary, with a period of rain showers immediately ahead of cold fropa.

Temperatures currently in the upper 40s/low 50s will quickly drop through the 40s behind the front, and eventually into the low-mid 30s later tonight with the stronger push of wind and cold advection around the base of the deepening low to our north. Scattered rain and snow showers are also expected to redevelop toward morning over far northern IL, as deeper moisture wraps around the circulation (currently noted in radar returns across far northwest IA/western MN). These should transition to all snow showers fairly quickly around daybreak, as indicated in going forecast.

Other than aforementioned details to timing/spatial resolution of the cold front and increasing winds more quickly behind the front overnight, remainder of the near term forecast is in good shape.

Ratzer

DISCUSSION

Issued at 233 PM CST Tue Nov 25 2025

Through Wednesday:

Conditions were slow to improve from the gloominess of this morning, but visibilities have since recovered and now we remain beneath a low-hanging stratus deck as we move through the afternoon. The low stratus kept temperatures on the cooler side today and now we're seeing lower 50s around the area.

Zooming out of the local area, we find a low pressure circulation over the eastern Dakotas and cold front moving across Iowa and extending southwest into the Plains. A line of light showers has developed along the front in recent hours and is moving across central IA as of this writing. These features will continue to progress eastward as the associated upper trough digs into the upper Midwest this evening. The line of showers is expected to approach the I-39 corridor early this evening and work across the CWA through the end of the evening. A few isolated showers may try and pop up ahead of this main line, but they would be very light and isolated. Coverage of showers should be pretty tightly confined to the front itself and should only reside over any given area for an hour or two. Chances are also highest across the northern CWA, where drier air may keep southern portions of the area dry.

No precip is expected immediately behind the front and through most of the overnight with a sharp cutoff in forcing and deeper moisture. However, a secondary frontal feature/baroclinic zone will swing across late tonight and reinvigorate some of those ingredients in its wake and boost precip chances again for very late tonight into tomorrow. Light precip, likely light rain, should move into our northwest during the predawn hours behind that secondary front and spread eastward. As we move closer to daybreak, rain should mix with snow for a brief period before a transition to all snow is expected around or shortly after sunrise. Periods of flurries and snow showers are then expected to persist through the afternoon. Coverage of any meaningful snow should be confined to areas near and especially north of I-80 with deeper moisture and better forcing nearer to low track, while flurries may materialize farther south. There is a possibility that we see some localized bands of moderate snowfall at times amid the steep low level lapse rates and strong shearing, although this does not appear to be a widespread concern. Best chance of this will also be north of I-80. Dustings to a couple of tenths of an inch are possible on cooler and elevated surfaces, including bridges and overpasses, but roads are expected to largely remain clear otherwise. However, can't entirely rule out a slick stretch following any heavier push of snow, mainly on less-busy roads. The falling snow in combination with strong winds (more on that below) may make for messy travel at times during the morning and afternoon commutes tomorrow. The column begins to dry out toward the end of the afternoon which will put an end to precip chances.

Focus is also on strong to potentially damaging winds expected in the wake of this evening's front. Following the passage of the front, cold advection will allow for efficient BL mixing into 30+ kt of low level flow. After daybreak, an uptick in the surface isallobaric component and low level wind field will result in regular 45 to 50+ mph gusts out of the west through the morning and afternoon. A few damaging gusts to near 60 mph will be possible. The strongest winds are generally expected across the northern CWA, but conditions look pretty similar area-wide. Be sure to secure any outdoor furniture and decorations before tomorrow. Also prepare for your vehicle to be pushed around a bit by the wind tomorrow, especially when traveling on open north-south roads. No changes were made to the Wind Advisory which goes into effect for the entire CWA at 3AM tonight and lasts into tomorrow evening. Gusts will ease during the evening, but stay up to near 25 to 30 mph through the night with another windy day in store for Thanksgiving.

Lastly, the cold advection and windy conditions will make for a noticeably cooler day tomorrow. Behind this cold front, 850mb temperatures are progged to drop about 25F between this evening and tomorrow evening. Surface temperatures will stay up near 50 ahead of the frontal passage, then steadily drop through the night bottoming out in the lower and middle 30s by tomorrow morning. Continued strong cold advection will keep temperatures nearly still from there. In fact, latest high-res guidance suggests we may start to cool a little earlier than usual tomorrow, early in the afternoon. The strong winds will keep wind chills in the teens and lower 20s during the day.

Doom

Wednesday Night through Tuesday:

Wednesday night and into Thanksgiving day, the surface low pressure system responsible for powerful winds across the Great Lakes region will lift northeastward into southern Quebec. A 1030 mb surface high pressure system building in the central plains will maintain a strong pressure gradient across the Great Lakes in the wake of the surface low, facilitating blustery northwest wind gusts of 30 to locally 40 mph throughout the day. As a result, Thanksgiving day is shaping up to be pretty chilly. Wind chills in the morning will be in the lower teens, and only "recover" to the mid 20s by mid-afternoon even as actual air temperatures rise toward the freezing mark. From both the actual and "feels like" temperature, Thanksgiving 2025 is shaping up to be the coldest in Chicago since 2014 when the high temperature was 27. (Rockford logged a high temperature of 29 on Thanksgiving day last year).

Thursday night into Friday, the surface high pressure system will shift eastward over the Mississippi River Valley leading to a calm and chilly night. Overnight lows will range from the mid teens in outlying areas to the mid 20s lakeside. While highs on Friday will be similar to Thanksgiving day, the lack of wind will make it feel quite a bit warmer.

Attention then turns toward the next storm system due to arrive in our region this weekend. Ensemble model guidance remains in agreement that an upper-level wave currently halfway between the states of Hawaii and Washington will come ashore and propagate eastward across the contiguous US on Friday and into the Mississippi River Valley on Saturday. As the wave approaches, it may attempt to phase with subtle preceding shortwaves emanating from the remnants of the subtropical jet along the US/Mexico border and a polar wave dropping south out of Canada. The degree of interaction with any of these waves will ultimately influence the eventual evolution of the storm system, which is leading to the usual spread of ensemble outcomes typical for a system 4 days out.

Generally speaking, the expectation is for a region of warm- air advection snow to develop across the region early Saturday morning and then to transition to "cold conveyer belt" frontogenesis-driven snow Saturday into Saturday night. Depending on the exact evolution and strength of the system, a warm nose may surge into parts of the area leading to a transition from snow to rain at some point on Saturday. Regardless, the ensemble signal, particularly among the EPS suite, remains strong for our general region to experience impactful snow on Saturday. At this point, the message for this weekend remains the same: Staying up to date on the forecast especially if planning to travel in the general region.

Borchardt

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 1042 PM CST Tue Nov 25 2025

Forecast concerns include...

Very strong westerly winds through Wednesday night. Chance of snow showers early Wednesday morning into afternoon. Mvfr cigs through the period.

The cold front will continue moving across northwest IN over the next few hours. Westerly winds will gust in the lower/mid 30kt range into the predawn hours and then gusts into the lower/mid 40kt range are expected through mid/late Wednesday afternoon with gusts diminishing into the lower/mid 30kt range Wednesday evening and into the mid 20kt range early Thursday morning.

Flurries and some snow showers are expected to spread across the area prior to daybreak and continue through early afternoon, ending from west to east. Some of these snow showers may reduce visibilities into the 2sm range, but these lower vis reductions will likely be brief.

A few hour period of low vfr cigs is expected early overnight and then prevailing mvfr cigs will spread back across the area and remain through Wednesday afternoon, slowly lifting through mvfr Wednesday night and then possibly to low vfr early Thursday morning. cms

MARINE

Issued at 233 PM CST Tue Nov 25 2025

Key Marine Messages include:

- A Gale Warning is in effect tonight through Thursday for the Illinois and Indiana nearshore waters of Lake Michigan.

- Peak wind gusts of 45 to 50 kt are expected on Wednesday, tapering to 35 to 40 kt on Thursday.

A powerful cold front tied to a approaching low pressure system will sweep across the area tonight. Westerly winds will increase markedly behind the cold front to gale force tonight, and increase further to nearly storm force Wednesday afternoon. Peak wind gusts of 45 to 50 kt are expected in the Illinois and Indiana nearshore waters of Lake Michigan on Wednesday, with higher wind gusts at high platform observation stations and over the open waters of Lake Michigan. While the magnitude of winds will gradually ease from Wednesday night onward, they will remain at or above gale force (35 to 40 kt) all the way through Thursday evening.

A Gale Warning is in effect for the Illinois and Indiana shorelines of Lake Michigan tonight through Thursday. A Storm Warning is in effect for the open waters of Lake Michigan on Wednesday before transitioning to a Gale Warning on Thursday.

Borchardt

LOT WATCHES/WARNINGS/ADVISORIES

IL...Wind Advisory from 3 AM to 9 PM CST Wednesday for ILZ003- ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013- ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103- ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Wind Advisory from 3 AM CST /4 AM EST/ to 9 PM CST /10 PM EST/ Wednesday for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Gale Warning from 3 AM Wednesday to 10 PM CST Thursday for the IL and IN nearshore waters.