Main snow event still expected here Saturday forenoon

As the main snowfall in the initial surge of snow slides off to our east and south, the main event is poised to lift out of Missouri tonight and spread east over the Chicago area during the pre-dawn hours and continue into the afternoon Saturday. The first surge left about a band of 2-inch snowfall along and just south of Interstate-80 this evening with just a dusting to a half-inch farther north. Peotone in Will County reported an inch and a half of new snow as of 10PM CST this evening.

Heavy snow is forecast to lay out over the Chicago area come morning with 5 to 10 inches still the going forecast by the time it lets up later in the day. There is a growing possibility of sleet and freezing rain mixed with snow along and south of Interstate-80 Saturday morning. The frozen precipitation will change back to snow before ending from west to east later in the afternoon/evening.

Light snow north of Interstate-88 and sneaking north

The heavier snow in central Illinois is very slowly working it’s way north – a steady light snow has crept north of interstate-88 with light snow reported in DeKalb, Aurora, St. Charles and at Midway Airport (past two hours). By 10PM the snow should be into northern Chicago, O’Hare, Elgin and farther west.

The heavier snowfall is also working it’s way north in western Illinois with 2 to 3 inches now on the ground in the Galesburg – Burlington, Iowa area – just south and east of the Quad-Cities.

Some west-central Illinois snowfall reports at 9PM CST…

Location                snowfall (inches)

Galesburg, Knox Co         2.5

Burlington, IA                   2.5

Fort Madison, IA              2.5

Stronghurst, IL                 3.0 (southeast of Burlington in Henderson Co IL)

Snowing north of Interstate-80 – movement northeast

At 6PM light snow was falling along and just north of Interstate-80 all the way from the Quad-Cities to Joliet – southern Cook County into northwestern Indiana. Heaviest snowfall in central Illinois had already accumulated 3 to 4 inches at several locations. The snow will slowly work its way north – covering Chicago and points north to the Illinois-Wisconsin state line later tonight.

 Some snowfall reports:

Location          snowfall (inches)

Astoria, Fulton Co         3.5

St. David, Fulton Co     4.0

Manito, Mason Co        3.6

Morton, Tazewell Co    3.2

Eureka, Woodford Co  3.0

High probability of heavy snow over Chicago area next 24 hours

The National Center for Environmental Prediction (NCEP) current probabilistic predictions have Chicago right in the middle of the highest probabilities for heavy snow in the next 24 hours.

The first chart below has northeast Illinois inside the red-banded area of better than 70 percent probability of 4-inches or more between 6PM CST this evening and 6PM CST Saturday. The second map has Chicago in the area of better than a 40 percent chance of 8 inches or more snowfall in that same 6PM CST today to 6PM CST Saturday.

Probabilty of 4-inches or more

Probability of 8-inches or more

Winter Storm Watch upgraded to Winter Storm Warning

Update 4PM CST

The Winter Storm Warning (pink-shaded area on map below) remains in effect for northeastern into west-central Illinois tonight and Saturday calling for 6 to 10 inches of snow with a chance of a mixture of heavy wet snow, sleet and freezing rain south of a line from Ottawa to Joliet to Midway.

Winter Weather Advisories for tonight and Saturday into Saturday evening (shaded purple areas) surround the Warning area with 3 to 6-inches of snow forecast far west (Iowa) and north (Wisconsin) and a mixture of freezing rain, sleet, and 3 to 6-inches of wet snow to the south (in Illinois) and east (Indiana and Lower Michigan.

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The Chicago National Weather Service Forecast Office has upgraded the previously issued Winter Storm Watch for the Chicago area to a Winter Storm Warning beginning at 9PM this evening and lasting until 6PM late Saturday afternoon/early evening. The warning calls for 6 to 10 inches of snow.

 The snowfall should begin this evening – spreading into our area from the southwest and gradually increasing overnight. Heaviest snowfall – perhaps as much as an inch/hour will most likely occur during the mid to late morning hours Saturday. There is still the possibility that precipitation could begin in southernmost counties in the form of freezing rain or sleet before changing over to a wet accumulating snow.

 Travelers should be alerted to very hazardous driving conditions beginning overnight and continuing during the day Saturday.

The National Hazards Map below depicts the Chicago area under the Winter Storm Warning (in pink) surrounded by Winter weather Advisories )purple-shaded) for heavy snow to our north and west and the Winter Storm Watch (blue-shaded) to our south and east.

This image displays watches, warnings, statements and advisories issued by the National Weather Service

Wind Chill Advisory in effect until 9AM CST Wednesday

The National Weather Service Forecast Office in Chicago has downgraded the Wind Chill Warning to a Wind Chill Advisory effective until 9AM CST Wednesday. Dangerously cold area wind chills peaked overnight and earlier this morning between -30 and -35 degrees..

With temperatures on the rise – expected to reach a dew degrees above zero this afternoon and wind speeds generally under 20 miles hour, wind chills the remainder of the day will run in  -15 to -25-degrees range. Overnight tonight (and early Wednesday morning), temperatures will fall back into the -5 to -10-degree level with wind chills mostly in the -20 to -25-degree range.

Sub-zero temperatures – dangerous wind chills across the Chicago area this morning

A Wind Chill Warning continues in effect across the Chicago area this morning. Dangerous wind chills ranged from about 25 below to 35 below with temperatures generally in the -10 to -15-degree range. Temperatures will probably rise very slowly this morning, but winds, which have been light (calm at a few locations) will pick up out of the west, so that wind chills will probably not change much during the forenoon – holding in the -25 to -30-degree range.

The temperature at Chicago’s official O’Hare observing site bottomed out at minus 11 degrees this morning – falling 2 degrees short of the all-time record low of -13 for this date set back in 1977.

Some low temperatures and coldest wind chills across the area this morning…

Location    Low temperature   coldest wind chill

O’Hare               -11                       -30

Midway              -11                       -28

Aurora               -14                       -31

Lansing             -13                       -29

Joliet                 -15                       -28

Waukegan        -13                       -27

Du Page Apt     -14                       -30

Wheeling          -11                       -26

Kankakee         -12                       -29

Morris               -13                       -30

Romeoville       -14                       -31

Northerly Island  -8                       -30

Rockford           -18                       -27 (Calm winds)

Rochelle           -16                       -34

DeKalb             -14                       -35

Gary, IN             -9                        -24

Valparaiso, IN  -14                      -31

Peru/Ottawa     -10                      -25

Temperatures on target to set record – Wind Chill Warning continues

 Temperatures are falling rapidly this evening under clear skies and a fresh snow cover. Readings at 9PM CST had reached double-digits below zero at a few locations – the lowest being a -10 degrees at DeKalb – followed closely by -9 at Rockford, Rochelle, and Waukegan. At the official O’Hare observation site the reading was a -6, just 7 degrees shy of the record -13 degree low for January 28th set back in 1977. Minimum temperatures are normally reached in the pre-dawn hours, so it’s likely we will establish a new record low – perhaps by several degrees.

Temperatures are still expected to bottom out at close to 10 below in the city (it’s already a -4 at the Northerly Island lakefront location), and closer to -20 degrees or even lower in locations along and beyond the Fox River Valley.  

Dangerous Wind Chills

 A Wind Chill warning is in effect until 9AM Wednesday morning for the entire Chicago area. With winds generally flowing from the west at 10 to 20 miles per hour, wind chills at 9PM ranged from -20 (Peru/Ottawa) to a -30 degrees (DeKalb). Most of the wind chill readings were in the negative middle 20s – all were trending colder.

Winds will be dying off a bit as the night goes on, but this will be more than balanced out by the falling temperatures. As a result, by the pre-dawn hours Tuesday and shortly after sunrise, very dangerous wind chills will most likely range from -30 degrees in the city and to the south, and -40 degrees or colder away from the city to the west and north.

Wind Chill Warning – record low temperatures likely tonight

The Wind Chill Warning for the Chicago area remains in effect until 9AM CST Wednesday morning. Tonight under clear skies with Arctic high pressure overhead, lighter winds, and the fresh snow cover, radiational heat loss should be significant. Temperatures already were falling during the late afternoon with almost all readings below zero.

Temperatures will probably be close to 10 below by or shortly after midnight tonight at many locations, and by tomorrow morning temperatures will be bottoming out between -15 and -20 degrees – some of the cold-prone sites even colder. Chicago’s January 28 record low temperature of minus 13 degrees set back in 1977 has a good chance of being broken.

Wind chills have been running in the -20 to -25-degree range this afternoon, and along with the temperatures, they will drop well into the very dangerous category later tonight. During the pre-dawn hours Tuesday morning wind chills will probably range from -30 degrees in southern sections including Chicago itself to -40 degrees north and west of the city.

 During the day Tuesday, temperatures will probably warm up close to or just above the zero-degree mark by early afternoon at many observing locations. But tomorrow night readings will again drop off – reaching -5 to -10-degrees before dawn Wednesday. Wind chills during the day will again run in the -20 to -25-degree range in the afternoon and overnight – improving by  Wednesday forenoon when the Wind Chill Warning is scheduled to expire.

 The National Hazards Map below depicts a broad band of Wind Chill Warnings and Advisories (gray and light blue-shaded areas) from the Dakotas through Minnesota and Iowa, Wisconsin and Illinois all the way through Ohio, Pennsylvania and New York into New England. Brutally-cold Wind chills of minus 40 to minus 55- degrees are expected tonight from North Dakota through Minnesota into northern Wisconsin. Note the Winter Strom Warnings up all along the Gulf Coast – starting up the east coast (pink and purple-shaded areas) from Texas all the way to southern Virginia for freezing rain, sleet and snow in the next 24 to 36 hours.

This image displays watches, warnings, statements and advisories issued by the National Weather Service