Total snowfalls were:
This map of snowfall accumulations for the 2-day period ending 7am on 22 January 2014 does not reflect the much higher but very localized reports of 20-24" around Griffith, Indiana. This map is derived from official NWS reporting stations as well as reports from trained observers using standardized equipment and measuring techniques in the CoCoRaHS network. These values are representative of general amounts over a wide area, but do not capture the highly localized nature of lake effect snow bands.
A strong Arctic cold front surged through northern Illinois and northwest Indiana on the afternoon of Monday January 20th. Air temperatures fell from the upper 20s to mid 30s as of late afternoon to the teens and lower 20s during the evening. At the same time, an upper level disturbance and surface trough began producing persistent light accumulating snow over the entire area mainly during the evening hours.
The 6pm radiosonde sounding out of Green Bay, WI sampled extremely cold temperatures at 850 mb (about 4,500 ft above the surface), of -22C (-7F). This airmass pouring down across the Lake Michigan waters of about 33-35F, set up an impressive thermodynamic environment that was very favorable for the formation of intense lake effect snow showers. As the inverted surface trough dropped southward during the mid and late evening, Arctic high pressure of nearly 1040 mb slowly built southeast from the northern Plains. Furthermore, a weak thermally induced low pressure formed over northern lower Michigan. The pressure gradient between these 3 features set-up a full northerly fetch of bitterly cold Arctic air down the length of Lake Michigan, with initial orientation of convergent flow into far northeastern Illinois. In addition, the upper level trough provided enhanced uplift through the favored snow growth zone of -12 to -18 degrees C.
A single band of heavy lake effect snow first impacted southeastern Lake County (IL) and northern Cook counties most significantly late Monday evening into the early overnight with snowfall rates of 1 to 2 inches per hour. As the wind convergence become more northerly, the band then sunk south along the Cook County shore, with impacts felt as far inland as central Kankakee County. By early Tuesday around 5 to 6am, north-northwest winds along the Illinois shore and east-northeast winds into Porter County Indiana, dramatically increased convergence into extreme northwestern Lake County Indiana. The development of at least one mesoscale low pressure area (mesolow) over the southern tip of the lake maintained this convergence for a much longer period of time over Lake County Indiana. The result was an intense single band of lake effect snow that produced 1 to 4 inch per hour snowfall rates and extreme snowfall amounts of 1.5 to 2 feet by early afternoon in the vicinity of Griffth, Hammond, East Chicago and Gary Indiana. During the most intense snowfall rates, whiteout conditions were common and major interstates such as 80/94 and I-65 became clogged with snow, bringing traffic to a standstill.
Despite the persistence of at least one mesolow through the mid afternoon and early evening, winds shifting to westerly across much of northwest Indiana, as well as less favorable thermodynamic conditions for lake effect snow resulted in the weakening of the band as it shifted east into Porter County.
Meteorology of the Heavy Lake Effect Snow Band on 1/21/14 (click to enlarge)
Radar Image of Intense Lake Effect Band at 8:25 am 1/21/14 (click to enlarge)
Radar 24-hour animation from 21 January 2014 showing evolution of lake effect snow band from Cook County into northwest Indiana, and persistence of this band for several hours (nearly 6 AM to 6 PM) over Lake County, Indiana.
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE CHICAGO IL 1051 PM CST TUE JAN 21 2014 SNOW REPORTS FROM VOLUNTEER OBSERVERS AND NWS OBS SITES. WE THANK EVERYONE FOR THEIR REPORTS DURING THIS EVENT! LOCATION OBSERVED TIME/DATE VALUE OF OBSERVATION LAT LON ILLINOIS ...COOK COUNTY... PARK FOREST 4.0 M 600 AM 01/21 41.48N 87.69W HARWOOD HEIGHTS 4.3 M 725 AM 01/21 41.97N 87.81W 2 SW SKOKIE 4.5 E 200 AM 01/21 42.02N 87.77W OHARE AIRPORT 5.9 M 558 AM 01/21 41.98N 87.90W 3 SW MIDWAY AIRPORT 6.1 M 337 AM 01/21 41.75N 87.79W ROGERS PARK 6.5 E 609 AM 01/21 42.01N 87.67W EVANSTON 6.6 M 455 AM 01/21 42.05N 87.69W NORTHBROOK 6.6 M 100 AM 01/21 42.13N 87.83W 1 S CHICAGO 6.9 E 548 AM 01/21 41.87N 87.63W NORTHBROOK 6.9 M 700 AM 01/21 42.13N 87.83W 3 SW MIDWAY AIRPORT 7.2 M 536 AM 01/21 41.75N 87.79W NORTHBROOK 11.8 M 600 AM 01/21 42.13N 87.83W ...DUPAGE COUNTY... GLEN ELLYN 3.0 M 200 AM 01/21 41.87N 88.06W ...LAKE COUNTY... HIGHLAND PARK 6.5 M 200 AM 01/21 42.18N 87.81W HIGHWOOD 6.8 M 700 AM 01/21 42.21N 87.81W ...WILL COUNTY... LOCKPORT 2.0 M 1230 AM 01/21 41.59N 88.05W ROMEOVILLE 2.0 M 600 AM 01/21 41.65N 88.09W 2 NW MOKENA 3.0 E 200 AM 01/21 41.55N 87.90W MOKENA 3.5 E 200 AM 01/21 41.53N 87.88W LOCATION OBSERVED TIME/DATE VALUE OF OBSERVATION LAT LON INDIANA ...JASPER COUNTY... REMINGTON 2.1 M 600 AM 01/21 40.76N 87.15W ...LAKE COUNTY... 4 N CHESTERTON 1.7 M 530 PM 01/21 41.66N 87.06W 5 SE MERRILLVILLE 1.8 M 600 PM 01/21 41.43N 87.24W CROWN POINT 3.5 M 315 PM 01/21 41.42N 87.36W MERRILLVILLE 4.0 E 1122 AM 01/21 41.47N 87.33W S HOBART 5.0 M 545 PM 01/21 41.53N 87.27W SCHERERVILLE 7.5 M 600 PM 01/21 41.49N 87.45W SCHERERVILLE 9.5 M 1139 AM 01/21 41.49N 87.45W SCHERERVILLE 10.0 E 1136 AM 01/21 41.49N 87.45W HIGHLAND 14.0 M 1245 PM 01/21 41.55N 87.46W HAMMOND 16.0 M 155 PM 01/21 41.62N 87.49W 3 SE EAST CHICAGO 20.0 E 700 PM 01/21 41.62N 87.41W GRIFFITH 20.0 E 1129 AM 01/21 41.52N 87.42W GRIFFITH 22.3 M 640 PM 01/21 41.52N 87.42W GRIFFITH 24.0 U 130 PM 01/21 41.52N 87.42W N GRIFFITH 24.0 E 230 PM 01/21 41.52N 87.42W