textproduct: Chicago

KEY MESSAGES

- Snow showers, with some sleet/graupel, early this morning. Travel impacts expected, mainly across the Chicago Metro area into northwest Indiana.

- Period of lake effect snow Friday night through Saturday in northwest Indiana.

- A pattern shift will occur next week towards warmer, and potentially wetter, conditions.

DISCUSSION

Issued at 323 AM CST Fri Feb 6 2026

Through Today:

Water vapor imagery this morning shows a potent shortwave diving south into the western Great Lakes. An area of snow associated with this shortwave covers much eastern/southeastern Wisconsin. Radar presentation of this snow definitely is convective in nature, unsurprisingly given the steep mid level lapse rates across the region. Have seen a number "unknown precipitation" reports from AWOS/ASOS sites across Wisconsin, given the high cloud bases and convective nature of the precipitation, suspect this is graupel or snow pellets.

Anticipate this area of snow, mixed at times with graupel, sleet, or snow pellets, to overspread about the northeast half or so of our CWA during the predawn hours, then rapidly end from northwest to southeast during the early-mid morning hours. Most concentrated area of precip and highest amounts should end up over the Chicago Metro area into extreme northwest Indiana, when a quick inch or so of snow could fall this morning. Certainly possible that there could be some heavier bursts of snow with the more intense convective elements. Roadways impacts are likely during the rush hour this morning.

Opted to remove freezing drizzle from the forecast as low levels should be too dry for drizzle and cloud bases too high. Opted to maintain a slight chance for some freezing rain, but plan to downplay that threat in messaging as convection deep enough for precipitation should also be deep enough to have ice nuclei present to support snow, graupel, or snow pellets. While snow looks to hit at an inopportune time, totals should be too light to warrant a winter weather advisory, so plan to re-issue and freshen up the special weather statement.

Gusty north-northwest winds will develop this morning and continue through the afternoon. While there could be a couple hours with some breaks in the clouds, stratocumulus should fill back in this afternoon. The cloud cover may temper the magnitude of the gusts some, but forecast soundings depict steep low level lapse rates tapping into 35-40kt winds a few thousand feet off the deck. Certainly possible we could see a couple gusts to 40 mph today, particularly with any clearing/partially clearing.

- Izzi

Tonight through Thursday:

A deepening trough is expected to be traversing across the Great Lakes tonight into Saturday with northern IL and northwest IN residing on the western periphery of said trough. While the drying mid-levels on the backside of the trough will allow precipitation to conclude for most of the area this afternoon/evening, increasing surface convergence over southern Lake Michigan will develop a band of lake effect snow for portions of northwest and northern IN. Forecast soundings show the lake effect parameters to be decent with ELs around 5000-5500 ft and steep low-level lapse rates (around 7-8C/km) residing within the DGZ which could allow for a localized couple inches of accumulation especially in eastern Porter County near the convergence axis. However, with ELs expected to be lowering overnight as high pressure builds in and northwest winds pushing the band more into northern IN there is a play for the bulk of any accumulation to stay east of our area. Given the finicky nature of lake effect there is a chance things could shift slightly as we get closer, but for now have kept our official forecast more in line with the more eastward solutions with highest POPs (30-50%) in eastern Porter County and northern IN and accumulations in the 0.5-1.0 inch range (highest again in eastern Porter County).

The lake effect will gradually wane Saturday morning with high pressure settling overhead giving as a quiet but chilly Saturday with highs in the mid to upper 20s. However, a shortwave trough is forecast to dive across the western Great Lakes late Saturday night into Sunday which may lead to a period of light snow showers and/or flurries for some. While guidance is in good agreement on the shortwave track and timing, forecast soundings show moisture (especially in the mid-levels) may be somewhat of a limiting factor and thus most of our area may remain dry. That said, given some decent low-level moisture and the combination of warm advection and ascent with the wave have opted to introduce some slight chance (15- 20%) POPs over far northeast IL and northwest IN in case some snow showers are able to materialize. Regardless any snow that does occur doesn't look to amount to much in the way of accumulations aside from maybe a light dusting.

Heading into next week, the northwest oriented upper pattern that has kept us in cold these past few weeks will begin to become more zonal (east-west oriented) by Monday. This shift will allow for more persistent periods of warm advection which in turn is expected to allow temperatures to moderate into the 40s to near 50 by the middle of the week. The only caveat though is a baroclinic zone that is forecast to establish across the mid-Mississippi Valley and western Great Lakes which could result in a gradient in temperatures if it were to set up overhead. Additionally, a couple of shortwaves are also forecast to traverse through the zonal flow (one over the Upper Midwest and northern Great Lakes and the other over the deep south) and may kick off some precipitation late Tuesday into Wednesday. If sufficient moisture can build into the area then precipitation should initially start off as rain Tuesday evening (with perhaps an isolated thunderstorm given the 6-7C/km lapse rates aloft) before transitioning to snow (or a rain/snow mix) as the baroclinic zone shifts south as a cold front on Wednesday. With a lot of uncertainty in quality of moisture return to our area have opted to maintain the 20-40% POPs late Tuesday through Wednesday for now.

Depending on how far south the aforementioned baroclinic zone gets Wednesday will determine whether or not additional periods of precipitation will occur throughout the rest of the week as more shortwaves pivot through the region. Given how guidance tends to struggle with baroclinic zones (especially 5-7 days out) saw no reason to change the 20-30% POPs offered by the NBM through the end of next week. However, do think that some dry periods will also be possible especially if the baroclinic zone can shift far enough south. Regardless, more typical temperatures for mid-February are forecast to close out next week with highs in the 30s to around 40 and overnight lows in the 20s.

Yack

AVIATION /12Z TAFS THROUGH 18Z SATURDAY/

Issued at 533 AM CST Fri Feb 6 2026

- IFR conditions with light snow/snizzle at Chicago area terminals early this morning, no additional accumulations expected.

- Strong/gusty northwest winds develop mid-morning and continue into this evening.

- Some flurries/very light snow showers possible this afternoon Chicago area terminals, no accumulations expected.

A brief period of IFR CIGS with some very small flaked light snow and/or snizzle or possibly brief freezing drizzle possible at ORD/MDW/GYY during the first couple hours of the TAFs. Expect any FZDZ to be very light and would not expect any icing on pavement.

Gusty northwest winds will develop by mid-morning which should mark the end to the threat of the very light precipitation. CIGS should lift to MVFR with those MVFR CIGS likely to persist through the afternoon into the evening.

There is a chance of some thin streamers of flurries or light snow showers later this afternoon into the immediate Chicago area terminals. If any flurries/snow showers occur, accumulations appear unlikely with very tiny snow flake/snow grains expected. Opted to leave MVFR VSBY in the PROB30, but confidence is pretty low in any VSBY restrictions below VFR.

MVFR CIGS will likely clear out tonight with winds gradually diminishing.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 3 AM CST Saturday for the IL nearshore waters.

Gale Warning from 10 AM this morning to midnight CST tonight for the IN nearshore waters.