Winter Weather Advisory, Arlington Heights, Northwest Cook County, O’Hare Weather Forecast; 2.7″ Snow Possible Monday Daytime

According to the National Weather Service Chicago, a band of lake effect snow will traverse the Chicago metro from Lake County/northern Cook County early Monday morning, January 6, 2025, into Chicago late morning through the afternoon, and NW Indiana this evening.

Localized rates in excess of 1-2″/hr could result in hazardous travel, including both the AM and PM commutes. Additional snow amounts up to 2-3″ possible, locally higher if the band stalls.

Patchy freezing drizzle may persist through this afternoon outside of the main lake effect band which could result in slick spots extending farther inland (20% chance).

There is a thin layer of ice on snow accumulation in some areas of Chicagoland.

Less than one-half inch of snowfall occurred overnight Sunday to Monday between 8:30 p.m. Sunday and 5:51 a.m. Monday. The low temperature overnight was about 21°F at 9:51 p.m. and the morning low was 21.9°F between 2:51 a.m. and 4:51 a.m.

Weather Radarat 6:45 a.m. Monday showed precipitation growing as Lake Effect Snow in a thin band along the Lake Michigan shoreline from the Milwaukee area and Lake County, Illinois and moving south toward lakefront suburbs and the City of Chicago.

See also Arlingtoncardinal.com/clouds

 O’HARE FORECAST … 

Monday: Snow showers likely, possibly mixed with freezing rain before noon, then snow showers. High near 28. North wind around 15 mph, with gusts as high as 30 mph. Chance of precipitation is 80%. Little or no ice accumulation expected. Total daytime snow accumulation of 1 to 3 inches possible.

Tonight: Isolated snow showers before 9pm. Partly cloudy, with a low around 15. North northwest wind 5 to 15 mph, with gusts as high as 25 mph. Chance of precipitation is 20%.

Tuesday: Partly sunny, with a high near 26. Northwest wind around 10 mph, with gusts as high as 15 mph.

Tuesday Night: Partly cloudy, with a low around 13. Northwest wind 5 to 10 mph, with gusts as high as 15 mph.

Wednesday: Partly sunny, with a high near 22. Northwest wind 5 to 10 mph.

Wednesday Night: Partly cloudy, with a low around 10.

Thursday: Sunny, with a high near 25.

Thursday Night: Mostly cloudy, with a low around 16.

Friday: Mostly cloudy, with a high near 26.

Friday Night: Mostly cloudy, with a low around 18.

Saturday: Partly sunny, with a high near 30.

Saturday Night: Mostly cloudy, with a low around 22.

Sunday: Mostly cloudy, with a high near 32.

WINTER WEATHER ADVISORY
URGENT – WINTER WEATHER MESSAGE
National Weather Service Chicago IL
420 AM CST Mon Jan 6 2025

DuPage-Central Cook- Including the cities of La Grange, Oak Lawn, Lombard, Downers Grove, Chicago, Oak Park, Carol Stream, Naperville, Wheaton, and Cicero 420 AM CST Mon Jan 6 2025

…WINTER WEATHER ADVISORY IN EFFECT UNTIL 4 PM CST THIS AFTERNOON…

* WHAT…Freezing drizzle and lake effect snow expected. Additional snow accumulations up to 2 to 3 inches and ice accumulations around a light glaze.

* WHERE…Central Cook and DuPage Counties.

* WHEN…Until 4 PM CST this afternoon.

* IMPACTS…Roads, and especially bridges and overpasses, will likely become slick and hazardous. Plan on slippery road conditions. The hazardous conditions could impact the morning and afternoon commutes.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

Slow down and use caution while traveling. The latest road conditions for Illinois can be obtained at www.gettingaroundillinois.com.

If you are going outside, watch your first few steps taken on stairs, sidewalks, and driveways. These surfaces could be icy and slippery, increasing your risk of a fall and injury.

During lake effect snow, the weather can vary from bands of locally heavy snow to dry weather just a few miles away. Visibilities can also vary greatly. Be prepared for rapid changes in weather, visibility, and road conditions.

 LAKE TEMPS … 

SOUTHERN LAKE MICHIGAN WATER TEMPERATURES
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CST Sun Jan 5 2025

LAKE MICHIGAN WATER TEMPERATURES…

CHICAGO SHORE………..32.

CHICAGO CRIB…………39.

MICHIGAN CITY………..35.

&&

M IS FOR MISSING DATA THAT IS NORMALLY AVAILABLE.

THE MICHIGAN CITY WATER TEMPERATURE SENSOR IS LOCATED AT
A WATER INTAKE ONE MILE OFFSHORE AND 60 FEET BELOW THE
WATER SURFACE. IT IS READ EVERY DAY OF THE YEAR.

FOR LAKE MICHIGAN WATER LEVELS, PLEASE SEE:
WWW.LRD.USACE.ARMY.MIL/WATER-INFORMATION/WATER-MANAGEMENT
/GREAT-LAKES-AND-HARBORS/WATER-LEVEL-FORECASTS

january.chicagoweatherstation.com

Arlingtoncardinal.com/radar

Chicago Weather Forecast for your MAC/PC/TABLET includes surrounding suburbs.

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Area Forecast Discussion
National Weather Service
Chicago/Romeoville, IL
556 AM CST Mon Jan 6 2025

.KEY MESSAGES…

– A band of lake effect snow will traverse the Chicago metro from Lake County/northern Cook County this morning into Chicago late morning through the afternoon, and NW Indiana this evening.

– Localized rates in excess of 1-2″/hr could result in hazardous travel, including both the AM and PM commutes. Additional snow amounts up to 2-3″ possible, locally higher if the band stalls.

– Patchy freezing drizzle may persist through this afternoon outside of the main lake effect band which could result in slick spots extending farther inland (20% chance).

&&

.DISCUSSION… Issued at 3:44 AM CST Mon Jan 6 2025

Through Tonight:

The broader system snowfall from the winter storm exiting the region early this morning still has a few ephemeral weak fgen/deformation bands bringing narrow axes of snow across the area, currently along a Ottawa to Joliet to South Chicago line and down in southern Livingston county. This activity will gradually weaken with time through daybreak with light snow ending from north to south with time with only an additional light dusting possible in spots near and south of I-80.

After an initial 1-2 inches of snow falling across Lake County, IL overnight, the lake effect band retreated back north out over Lake Michigan early this morning and become rather disorganized. As of this writing, the band is starting to consolidate again, with northwesterly winds observed across southeast Wisconsin highlighting the strengthening convergence axis (also evident on KMKX and KGRB radars). The general motion of the band has been toward the southwest with time which will bring the band back inland across Lake and Cook Counties within the hour, resuming at least light accumulations (0.1-0.3″/hr) and reduced visibility in those areas.

There remains slight differences among the various hi-res models available with the placement and orientation of the lake effect band through the day today, however, the general expectation is for it to continue its westward progress further west into Lake County and northern Cook County (and potentially as far inland as DuPage) this morning. Timing when it begins to retreat back to the east is a little less certain, with a slight trend in guidance toward a slower timing. Opted to not make too many big changes to the inherited precipitation forecast but did pull the higher probabilities further west to account for this slower eastward shift.

Approximate Timing: – Lake, IL, Northern Cook, DuPage: This morning into early afternoon. – Central, Southern Cook: Late morning through early Evening. – Lake, Porter, IN: This evening and overnight

While mottled inversion heights are only getting cloud tops into the lower part of the DGZ, very strong ascent (due to strong convergence) would support the potential for locally higher rates of 1-2″/hr. This could result in quickly deteriorating conditions within the core of the lake effect band. While there is concern that the band could stall, the general expectation is for it to make steady eastward progress as it rounds the shoreline through the day, with any given location only seeing the highest snowfall rates for ~1-2 hrs. Forecast snowfall amounts (in addition to what fell overnight) are in the 2-3″ range, which locally higher amounts possible if the band stalls.

With all of this said, have opted to add northern Cook County into the Winter Weather Advisory. Will let the day shift get another look at things to determine if this needs to be expanded to include the rest of Cook (potentially even DuPage), and Lake/Porter in Indiana. An SPS will be issued for those areas in the meantime.

Freezing Drizzle Today:

Late last evening freezing drizzle blossomed across much of northern Illinois (north of I-80). This was likely due to slightly shallower inversion heights occurring than forecast, which kept cloud top temperatures just warm enough (8-10C) to limit ice nucleation, particularly where ascent was weakest outside of the fgen/deformation snow bands and any lake effect snow. This resulted in a light glaze of ice on untreated roads, sidewalks, and parking lots in some areas. There is a concern that at least patchy freezing drizzle could persist into the day today. While snow is expected to be the predominant precipitation type within the center of the lake effect snow band, on the outer fringes, ascent begins to weaken in the lower levels and inversion heights appear to lower just enough. The big question mark is whether saturation is deep enough to support light drizzle or mist. In spite of this, it felt prudent to include at least a slight chance (20%) of freezing drizzle in the forecast.

Temperatures:

Temperatures are forecast to warm into the mid-upper 20s to near 30 near Lake Michigan. Breezy north to northeast winds will keep wind chills in the teens this afternoon. Lows tonight then drop into the low teens where clouds clear out, and upper teens to low 20s where lake effect clouds persist.

— Petr/NWS Chicago

Tuesday through Sunday:

A weak ridge will bring dry conditions Tuesday into Tuesday night. The one exception will be a chance for residual lake effect clouds and flurries across northeast Porter County amid persistent northwest flow.

A strong mid-level wave over western Ontario Tuesday night will encounter a rather dry environment as it rotates across the western Great Lakes Wednesday into Wednesday night. Synoptic precip should remain northeast of the area over Lower Michigan. However, veering low-level flow behind the wave and east of a strengthening surface ridge should bring LES into northwest Indiana Wednesday night and perhaps even near the Illinois shore Thursday morning.

After a passing ridge late Thursday, a deep mid-level wave will shift across the region Friday and Friday night as a secondary trough over northwest Mexico ejects ENE. Guidance is coming into better agreement that there will be a phasing component of the two waves, though the exact degree of phasing will have major implications on the broader evolution of the system across the Ohio and Mississippi river valleys. The latest trends would support at least some accumulating snow over portions (southeast) or all of the forecast area Friday into Friday night.

Temps will remain below normal through the upcoming weekend, though the coldest arctic air will remain well north of the area in Canada. Expect daytime highs in the 20s to be common. Low temps will be locally augmented where snowpack develops over the next couple days, but overall will be in the single digits above zero to the teens.

Kluber

&&

.AVIATION /12Z
TAFS THROUGH 18Z TUESDAY/…
Issued at 556 AM CST Mon Jan 6 2025

The previously expected lake effect snow early this morning has struggled to fully transition from FZDZ to SN, with the main lake effect snow band remaining offshore before spreading out and weakening to FZDZSN. With overall conditions likely to remain stagnant for at least a few hours, have maintained FZDZSN mention with intermittent IFR visibility in SHSN.

The main lake effect band should finally transition to all SN late this morning just west of ORD, then shift across ORD in the 18-21Z window and MDW in the 20-23Z window. The snow band could produce snowfall rates around 1″/hr, resulting in IFR to briefly LIFR visibility.

Frequent gusts to 25 knots are expected through the day, with the direction favoring NNW through mid-morning before shifting NNE as the lake effect band settles west of ORD/MDW. Winds will then shift back NNW behind the main lake effect band this afternoon. BKN high-end MVFR ceilings will diminish this evening as NW winds diminish to under 10 knots through Tuesday morning.

— Kluber/NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES… IL…

Winter Weather Advisory until 4 PM CST this afternoon for ILZ006-ILZ013-ILZ103-ILZ104.

IN…None. LM…Small Craft Advisory until 9 AM CST Tuesday for the IL nearshore waters.

Small Craft Advisory until 3 PM CST Tuesday for the IN nearshore waters.