Recap of the December 20th Winter Weather Event

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Snowfall Amounts

Local Area Snowfall

Local Area Snowfall Map

Regional Snowfall

Regional Snowfall Map

Illinois December 20th Snowfall Totals

Illinois Snowfall

Iowa Storm Total Snowfall

Iowa Snowfall

 

Wisconsin Storm Total Snowfall

Wisconsin Snowfall

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
1127 AM CST FRI DEC 21 2012 /1227 PM EST FRI DEC 21 2012/

...SNOWFALL REPORTS FROM THE DECEMBER 20TH EVENT...

THE FOLLOW ARE SNOW AMOUNTS FROM THE OFFICIAL CLIMATE SITES ACROSS
THE AREA:
                                               SNOW
  LOCATION:                                    FALL(INCHES)

  ROCKFORD......................................1.4
  CHICAGO (O`HARE INTERNATIONAL AIRPORT)........0.3


THE FOLLOWING ARE SNOW AMOUNTS FOR THE PREVIOUS 24-HOURS TAKEN BY
NWS COOPERATIVE...COCORAHS...CAST...AND RAST OBSERVERS. OBSERVATIONS
ARE USUALLY TAKEN AT 7 AM.


NORTHERN ILLINOIS                              SNOW
  LOCATION (COUNTY):                           FALL(INCHES)

  MOUNT MORRIS (OGLE)...........................4.4
  MACHESNEY PARK 3ENE (WINNEBAGO)...............4.0
  ROCKTON 1ESE (WINNEBAGO)......................3.6
  CAPRON (BOONE)................................3.5
  ROCKFORD 3NE (WINNEBAGO)......................3.5
  ROCKFORD 2ENE (WINNEBAGO).....................3.5
  ROSCOE 2ESE (WINNEBAGO).......................3.2
  ROSCOE 2SE (WINNEBAGO)........................3.2
  PAW PAW (LEE).................................3.0
  ROCKFORD 4NW (WINNEBAGO)......................2.8
  ELGIN 2W (KANE)...............................2.7
  WOODSTOCK (MCHENRY)...........................2.3
  HARVARD (MCHENRY).............................2.3
  LAKE ZURICH (LAKE)............................2.2
  ROCKFORD 1NW (WINNEBAGO)......................2.0
  GENOA (DE KALB)...............................1.9
  HUNTLEY 4W (MCHENRY)..........................1.9
  BULL VALLEY 2WNW (MCHENRY)....................1.8
  LAKE VILLA 1SSW (LAKE)........................1.7
  HARVARD (MCHENRY).............................1.5
  INVERNESS 2S (COOK)...........................1.4
  ALGONQUIN 1N (MCHENRY)........................1.4
  ROCKFORD (WINNEBAGO)..........................1.4
  SPRING GROVE 2N (MCHENRY).....................1.4
  ST. CHARLES 6NW (KANE)........................1.3
  HAWTHORN WOODS 1N (LAKE)......................1.3
  BYRON 3N (OGLE)...............................1.3
  MUNDELEIN (LAKE)..............................1.3
  ELGIN (KANE)..................................1.2
  PALATINE 1E (COOK)............................1.2
  BEACH PARK 1W (LAKE)..........................1.2
  BUFFALO GROVE 2N (LAKE).......................1.2
  ARLINGTON HEIGHTS 2NNW (COOK).................1.1
  BARRINGTON (LAKE).............................1.0
  BARTLETT 1SSE (DU PAGE).......................1.0
  FOX LAKE 2SE (LAKE)...........................1.0
  PONTIAC (LIVINGSTON)..........................1.0
  STREATOR (LIVINGSTON).........................1.0
  YORKVILLE 2SE (KENDALL).......................1.0
  GURNEE 2W (LAKE)..............................0.9
  WONDER LAKE 1WNW (MCHENRY)....................0.9
  ST CHARLES 7NW (KANE).........................0.9
  PLAINFIELD 5SW (KENDALL)......................0.8
  MENDOTA 1N (LA SALLE).........................0.8
  MCHENRY (MCHENRY).............................0.8
  BEECHER (WILL)................................0.7
  DE KALB (DE KALB).............................0.7
  GENEVA 3WSW (KANE)............................0.7
  DIXON 2SW (LEE)...............................0.7
  LINCOLNSHIRE 1.3WSW (LAKE)....................0.7
  WOODSTOCK 2WSW (MCHENRY)......................0.7
  WOODSTOCK 5NW (MCHENRY).......................0.7
  HOFFMAN ESTATES 5W (COOK).....................0.6
  DOWNERS GROVE (COOK)..........................0.6
  CORTLAND (DE KALB)............................0.6
  YORKVILLE 1W (KENDALL)........................0.6
  WAUKEGAN 2N (LAKE)............................0.6
  MIDWAY 3SW (COOK).............................0.6
  ELBURN (KANE).................................0.5
  PARK RIDGE (COOK).............................0.5
  SCHAUMBURG 2SW (COOK).........................0.5
  SCHAUMBURG 2S (COOK)..........................0.5
  ELK GROVE VILLAGE 1ESE (COOK).................0.5
  OAK PARK 1NNE (COOK)..........................0.5
  LA GRANGE PARK 1SSW (COOK)....................0.5
  AURORA 4SE (DU PAGE)..........................0.5
  OSWEGO 5SSE (KENDALL).........................0.5
  YORKVILLE 1NE (KENDALL).......................0.5
  BATAVIA 1WSW (KANE)...........................0.5
  GENEVA 2WSW (KANE)............................0.5
  GENEVA 1SSW (KANE)............................0.5
  PINGREE GROVE 1NW (KANE)......................0.5
  ELBURN (KANE).................................0.5
  DIXON 3NNW (LEE)..............................0.5
  RIVERWOODS (LAKE).............................0.5
  LAKEMOOR 2SE (LAKE)...........................0.5
  MARSEILLES 6WNW (LA SALLE)....................0.5
  NEW LENOX 2SE (WILL)..........................0.5
  OAK BROOK (DU PAGE)...........................0.5
  BATAVIA (KANE)................................0.4
  BOURBONNAIS (KANKAKEE)........................0.4
  ELGIN (KANE)..................................0.4
  GLEN ELLYN (DU PAGE)..........................0.4
  ELMHURST 1ESE (DU PAGE).......................0.4
  ELGIN 1S (KANE)...............................0.4
  AMBOY (LEE)...................................0.4
  LA SALLE (LA SALLE)...........................0.4
  ORLAND PARK 5WNW (WILL).......................0.4
  JOLIET 2N (WILL)..............................0.4
  STEWARD (LEE).................................0.4
  ELK GROVE VILLAGE 2WSW (COOK).................0.3
  WESTMONT 1SSE (DU PAGE).......................0.3
  AURORA 4SE (DU PAGE)..........................0.3
  CAROL STREAM (DU PAGE)........................0.3
  AURORA 4NE (DU PAGE)..........................0.3
  BONFIELD 4WSW (KANKAKEE)......................0.3
  SUGAR GROVE 1NE (KANE)........................0.3
  BATAVIA 2WNW (KANE)...........................0.3
  NORTH AURORA 2NE (KANE).......................0.3
  ELBURN 3NNE (KANE)............................0.3
  BATAVIA 1WNW (KANE)...........................0.3
  GENEVA 1N (KANE)..............................0.3
  LAKE BLUFF 1W (LAKE)..........................0.3
  SENECA 2SSW (LA SALLE)........................0.3
  OTTAWA 2N (LA SALLE)..........................0.3
  MENDOTA 2SE (LA SALLE)........................0.3
  MORRIS (GRUNDY)...............................0.3
  OHARE (COOK)..................................0.3
  COAL CITY 4NNW (GRUNDY).......................0.2
  OAK PARK 2S (COOK)............................0.2
  CHICAGO RIDGE (COOK)..........................0.2
  WORTH (COOK)..................................0.2
  OAK PARK 1SW (COOK)...........................0.2
  BURNHAM-HEGEWISCH 2NNW (COOK).................0.2
  GLEN ELLYN 2SSE (DU PAGE).....................0.2
  LISLE 1SE (DU PAGE)...........................0.2
  GLEN ELLYN 1SE (DU PAGE)......................0.2
  NAPERVILLE 1NW (DU PAGE)......................0.2
  DWIGHT 4NNW (GRUNDY)..........................0.2
  MORRIS 6ESE (GRUNDY)..........................0.2
  MONTGOMERY 1SSE (KENDALL).....................0.2
  MONTGOMERY 2SSE (KENDALL).....................0.2
  BOURBONNAIS 2NNE (KANKAKEE)...................0.2
  KANKAKEE 3SE (KANKAKEE).......................0.2
  LINCOLNSHIRE 1N (LAKE)........................0.2
  SHERIDAN (LA SALLE)...........................0.2
  CRETE 3E (WILL)...............................0.2
  PEOTONE (WILL)................................0.2
  NEW LENOX 3E (WILL)...........................0.2
  JOLIET (WILL).................................0.2
  JOLIET LOCK/DAM (WILL)........................0.2
  ROMEOVILLE (WILL).............................0.2
  MILFORD (IROQUOIS)............................0.2
  PLAINFIELD (WILL).............................0.2
  LISLE MORTON ARB (DU PAGE)....................0.2
  DRESDEN LOCK/DAM (GRUNDY).....................0.1
  DE KALB (DE KALB).............................0.1
  FAIRBURY (LIVINGSTON).........................0.1
  MELROSE PARK 2NW (COOK).......................0.1
  PARK FOREST 1NNE (COOK).......................0.1
  COUNTRYSIDE 1ENE (COOK).......................0.1
  LINCOLNWOOD 2E (COOK).........................0.1
  BOLINGBROOK 3NE (DU PAGE).....................0.1
  DOWNERS GROVE 2SE (DU PAGE)...................0.1
  BURR RIDGE 2SW (DU PAGE)......................0.1
  ROSELLE 1ESE (DU PAGE)........................0.1
  COAL CITY (GRUNDY)............................0.1
  MARSEILLES 3NW (LA SALLE).....................0.1
  MANHATTAN 5ENE (WILL).........................0.1
  HOMER GLEN 4WNW (WILL)........................0.1
  PEOTONE (WILL)................................0.1
  JOLIET 1ENE (WILL)............................0.1
  KANKAKEE (KANKAKEE)...........................0.1
  MANHATTAN (WILL)..............................0.1
  MONEE (WILL)..................................0.1
  PEOTONE (WILL)................................0.1
NORTHWEST INDIANA                              SNOW
  LOCATION (COUNTY):                           FALL(INCHES)

  VALPARAISO 1ENE (PORTER)......................2.2
  VALPARAISO 1NNW (PORTER)......................1.8
  VALPARAISO 5NNE (PORTER)......................1.6
  VALPARAISO 5NNE (PORTER)......................1.6
  DE MOTTE 6S (JASPER)..........................1.5
  VALPARAISO 2NW (PORTER).......................1.3
  VALPARAISO (PORTER)...........................1.2
  LAKE VILLAGE (NEWTON).........................1.2
  WHEATFIELD 3S (JASPER)........................1.1
  RENSSELAER 2N (JASPER)........................1.0
  VALPARAISO 1SE (PORTER).......................1.0
  VALPARAISO 7WSW (PORTER)......................1.0
  VALPARAISO 2N (PORTER)........................1.0
  HEBRON 4NE (PORTER)...........................0.8
  CROWN POINT 8E (PORTER).......................0.7
  VALPARAISO 4SW (PORTER).......................0.6
  DE MOTTE 1NNW (JASPER)........................0.5
  DE MOTTE 1SSW (JASPER)........................0.5
  REMINGTON (JASPER)............................0.5
  HIGHLAND (LAKE)...............................0.5
  KENTLAND 1NNW (NEWTON)........................0.5
  VALPARAISO 6SSW (PORTER)......................0.5
  VALPARAISO 6WSW (PORTER)......................0.5
  RENSSELAER (JASPER)...........................0.5
  DE MOTTE 4SW (JASPER).........................0.4
  REMINGTON (JASPER)............................0.4
  SCHERERVILLE 2WSW (LAKE)......................0.3
  MOUNT AYR 2NNE (NEWTON).......................0.3
  HOBART 1SSW (LAKE)............................0.2
  PORTAGE 1ESE (PORTER).........................0.2
  CROWN POINT 2WSW (LAKE).......................0.1
  CROWN POINT 1N (LAKE).........................0.1

$$

MTF/WEN

Rainfall

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
0645 AM CST FRI DEC 21 2012

...RECORD DAILY MAXIMUM RAINFALL SET AT ROCKFORD IL...

 A RECORD RAINFALL OF 1.27 INCHES WAS SET AT ROCKFORD IL
ON THURSDAY. THIS TIES THE OLD RECORD OF 1.27 SET IN 2012.


$$

Wednesday Night's Rainfall

MAXIMUM/MINIMUM TEMPERATURE AND PRECIPITATION TABLE
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
830 AM CST THU DEC 20 2012

TEMPERATURES AND 24 HOUR PRECIPITATION ENDING AT INDICATED TIME
THIS MORNING. LOCATIONS GROUPED BY CLIMATIC DIVISION.

DATA PROVIDED BY NATIONAL WEATHER SERVICE COOPERATIVE OBSERVERS.

.BR LOT 1220 C DH07/TAIRZX/TAIRZN/PPDRZZ/SFDRZZ/SDIRZZ

:                                                  SNOW  SNOW
:LOCATION               DATE/TIME  MAX  MIN  PCPN  FALL  DEPTH
:NORTHEAST ILLINOIS...
ARRI2: AURORA         :   DH0700/  42 / 31 / 1.07 /  0.0/    0
BARI2: BARRINGTON 3SW :   DH0700/  40 / 29 / 0.92 /  0.0/    0
CBGI2: BOTANIC GARDENS:   DH0800/  44 / 31 / 0.97 /  0.0/    0
MDWI2: MIDWAY 3SW     :   DH0700/  43 / 34 / 1.02 /  0.0/    0
DEKI2: DEKALB         :   DH0700/  41 / 29 / 0.45 /  0.0/    0
CDII2: CHANNAHON      :   DH0600/  45 / 34 / 1.00 /  0.0/    0
ELBI2: ELBURN         :   DH0600/     /    / 0.78 /  0.0/    0
ELGI2: ELGIN          :   DH0700/  41 / 30 / 0.83 /  0.0/    0
ERVI2: EARLVILLE      :   DH0600/     /    / 0.65 /  0.0/    0
GEOI2: GENOA          :   DH0700/     /    / 0.58 /  0.0/    0
HVDI2: HARVARD        :   DH0700/     /    / 0.58 /  0.0/    0
JOLI2: JOLIET LOCK/DAM:   DH0600/  43 / 32 / 0.85 /  0.0/    0
LNNI2: LA GRANGE      :   DH0600/     /    / 1.26 /  0.0/    0
LNSI2: LANSING        :   DH0700/     /    / 0.93 /  0.0/    0
WHTI2: LISLE MORTN ARB:   DH0700/  43 / 31 / 0.97 /  0.0/    0
MATI2: MANHATTAN  5NE :   DH0700/     /    / 0.94 /  0.0/    0
MMOI2: MARSEILLES     :   DH0600/  43 / 33 / 0.85 /  0.0/    0
MHYI2: MCHENRY        :   DH0800/  41 / 28 / 0.73 /  0.0/    0
MDTI2: MENDOTA        :   DH0700/     /    / 0.40 /  0.0/    0
MOEI2: MONEE          :   DH0800/     /    / 1.00 /  0.0/    0
MOSI2: MORRIS         :   DH0800/  48 / 33 / 1.01 /  0.0/    0
MUNI2: MUNDELEIN      :   DH0700/  40 / 28 / 0.87 /  0.0/    0
NWKI2: NEWARK 2SSE    :   DH0600/     /    / 0.97 /  0.0/    0
OKKI2: OAK BROOK      :   DH0800/     /    / 0.95 /  0.0/    0
OTTI2: OTTAWA 4SW     :   DH0800/  47 / 33 / 0.82 /  0.0/    0
PKFI2: PARK FOREST    :   DH0700/  44 / 33 / 0.93 /  0.0/    0
PEOI2: PEOTONE        :   DH0600/     /    / 0.90 /  0.0/    0
PFDI2: PLAINFIELD     :   DH0700/     /    / 1.14 /  0.0/    0
SGVI2: SPRING GROVE   :   DH0700/     /    / 0.96 /  0.0/    0
SCKI2: ST CHARLES 7NW :   DH0700/     /    / 0.74 /  0.0/    0
STAI2: STREATOR       :   DH0700/  49 / 36 / 0.80 /  0.0/    0
WODI2: WOODSTOCK 5NW  :   DH0700/     /    / 0.74 /  0.0/    0
YOKI2: YORKVILLE 2SE  :   DH0700/     /    / 1.01 /  0.0/    0
:                                                  SNOW  SNOW
:LOCATION               DATE/TIME  MAX  MIN  PCPN  FALL  DEPTH
:NORTHWEST ILLINOIS...
AMBI2: AMBOY          :   DH0800/     /    / 0.42 /  0.0/    0
PAWI2: PAW PAW        :   DH0700/  41 / 29 / 0.23 /  0.0/    0
RCHI2: ROCHELLE       :   DH0600/  40 / 30 / 0.49 /  0.0/    0
RSCI2: ROSCOE         :   DH0630/     /    / 0.61 /    T/    0
STWI2: STEWARD        :   DH0700/     /    / 0.34 /  0.0/    0
:                                                  SNOW  SNOW
:LOCATION               DATE/TIME  MAX  MIN  PCPN  FALL  DEPTH
:NORTHWEST INDIANA...
LVGI3: LAKE VILLAGE   :   DH0800/     /    / 0.77 /  0.0/    0
LLLI3: LOWELL         :   DH0700/  45 / 33 / 1.12 /  0.0/    0
MORI3: MOROCCO        :   DH0600/     /    / 0.60 /  0.0/    0
RMGI3: REMINGTON      :   DH0600/     /    / 0.59 /  0.0/    0
RZZI3: RENSSELAER     :   DH0730/  45 / 35 / 0.68 /  0.0/    0
VPOI3: VALPARAISO 5NNE:   DH0700/  42 / 35 / 0.88 /  0.0/    0
:                                                  SNOW  SNOW
:LOCATION               DATE/TIME  MAX  MIN  PCPN  FALL  DEPTH
:EASTERN ILLINOIS...
BOUI2: BOURBONNAIS    :   DH0700/     /    / 1.10 /  0.0/    0
CHTI2: CHATSWORTH     :   DH0700/     /    / 0.90 /  0.0/    0
CWWI2: DWIGHT         :   DH0700/  46 / 32 / 0.78 /  0.0/    0
FRBI2: FAIRBURY       :   DH0700/     /    / 0.72 /  0.0/    0
KKEI2: KANKAKEE       :   DH0700/  46 / 34 / 1.07 /  0.0/    0
MFDI2: MILFORD 5NW    :   DH0800/     /    / 0.66 /  0.0/    0
PXNI2: PAXTON         :   DH0700/  47 / 32 / 0.78 /  0.0/    0
SAAI2: ST ANNE        :   DH0700/     /    / 0.78 /  0.0/    0
.END
OTHER ADDITIONAL SUPPLEMENTARY REPORTS
                                                   SNOW  SNOW
:LOCATION               DATE/TIME  MAX  MIN  PCPN  FALL  DEPTH
BATI2: BATAVIA        :   DH0600/  41 / 31 / 0.62 /  0.0/    0
CTYI2: COAL CITY 4NNW :   DH0500/  43 / 34 / 0.77 /  0.0/    0
EGNI2: ELGIN          :   DH0729/     /    / 0.78 /  0.0/    0
JKJI2: JOLIET  2N     :   DH0700/     /    / 1.15 /  0.0/    0
JLEI2: JOLIET         :   DH0600/     /    / 0.99 /  0.0/    0
LKZI2: LAKE ZURICH    :   DH0700/     /    / 0.96 /  0.0/    0
PNEI2: PEOTONE        :   DH0600/     /    / 0.96 /  0.0/    0
ROFI2: ROCKFORD 4NNW  :   DH0700/     /    / 0.62 /    T/    0

SOIL TEMPERATURES AT 4 INCH DEPTH UNDER BARE SOIL
:LOCATION                MAX  MIN
CBGI2: BOTANIC GARDENS:  40 / 37
:
SOIL TEMPERATURES AT 4 INCH DEPTH UNDER SOD
:LOCATION                MAX  MIN
CBGI2: BOTANIC GARDENS:  44 / 43
:
NWS CHICAGO/ROMEOVILLE 4 INCH SOIL TEMP AT 8 AM
LOTI2:  ROMEOVILLE    :  40

THESE DATA ARE PRELIMINARY AND HAVE NOT UNDERGONE FINAL QUALITY
CONTROL BY THE NATIONAL CLIMATIC DATA CENTER /NCDC/.  THEREFORE...
THESE DATA ARE SUBJECT TO REVISION. FINAL AND CERTIFIED CLIMATE DATA
CAN BE ACCESSED AT WWW.NCDC.NOAA.GOV.

$$
 

Maximum Wind Gusts

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
426 AM CST FRI DEC 21 2012
...HIGHEST WINDS IN THE PAST 24 HOURS...
...LOCATION...          ...TIME...         ...WIND...
3 WNW MICHIGAN CITY (MARINE )  1215 AM DEC 21      66 MPH
3 SSE STEWARD (LEE IL) (MESOWEST)415 PM DEC 20       60 MPH
1 W CARBON HILL (GRUNDY IL) (APRSWXNET)1224 AM DEC 21       59 MPH
GIBSON CITY (FORD IL) (MESONET)818 PM DEC 2056 MPH
PONTIAC (LIVINGSTON IL) (AWOS)   635 PM DEC 20       55 MPH
PERU (LA SALLE IL) (AWOS)535 PM DEC 20      54 MPH
MORRIS (GRUNDY IL) (AWOS)  935 PM DEC 20     54 MPH
BURNS HARBOR (MARINE ) (GLOS) 1150 PM DEC 20     52 MPH
CHICAGO HARRISON-DEVER CRIB (MARINE ) 315 AM DEC 21     52 MPH
UTICA (LA SALLE IL) (HADS)600 PM DEC 2052 MPH
1 E SYCAMORE (DE KALB IL) (MESOWEST) 604 PM DEC 20     51 MPH
DUPAGE AIRPORT (DUPAGE IL) (ASOS) 1148 PM DEC 2051 MPH
2 WNW DIXON (LEE IL) (APRSWXNET)345 PM DEC 20     49 MPH
ROCHELLE (OGLE IL) (AWOS)  1055 PM DEC 20     48 MPH
CHEBANSE (IROQUOIS IL) (MESOWEST) 931 PM DEC 20     47 MPH
GREATER KANKAKEE AIRPORT (KANKAKEE IL)1215 AM DEC 21     47 MPH
3 SSW MINOOKA (GRUNDY IL) (HADS)     200 AM DEC 21     47 MPH
RENSSELAER (JASPER IN) (AWOS) 1255 AM DEC 21     46 MPH
2 WNW BURNHAM (COOK IL) (HADS)800 PM DEC 2046 MPH
AURORA MUNICIPAL AIRPORT (KANE IL)  646 PM DEC 20     46 MPH
OHARE INTL AP (COOK IL) (ASOS)839 PM DEC 20     45 MPH
DE KALB (DE KALB IL) (AWOS) 155 AM DEC 21     45 MPH
WAUKEGAN HARBOR (MARINE ) (GLOS)740 AM DEC 20     45 MPH
NWS CHICAGO WFO (WILL IL) (AWOS)115 AM DEC 21     44 MPH
PAL-WAUKEE AIRPORT (COOK IL) (ASOS) 842 PM DEC 20 44 MPH
3 NE PALATINE (COOK IL) (MESOWEST)101 AM DEC 21     44 MPH
3 N CARBON HILL (GRUNDY IL) (APRSWXNET)725 PM DEC 20     43 MPH
OTTAWA (LA SALLE IL) (APRSWXNET)1139 AM DEC 2043 MPH
1 W BATAVIA (KANE IL) (APRSWXNET)    732 PM DEC 20     43 MPH
1 ENE SPRING GROVE (MCHENRY IL)    1153 PM DEC 20     42 MPH
ROSEMONT (COOK IL) (APRSWXNET)  820 PM DEC 20     42 MPH
PEOTONE (WILL IL) (APRSWXNET)350 AM DEC 21 42 MPH
1 SE SOUTH CHICAGO (COOK IL)      348 AM DEC 21     41 MPH
5 NE MOROCCO (NEWTON IN) (APRSWXNET)1234 PM DEC 20     41 MPH
1 WNW NEW CHICAGO (LAKE IN) (INDOT)124 PM DEC 20 41 MPH
CHICAGO/ROCKFORD INTERNATIONAL AP         754 PM DEC 20     41 MPH
 3 NW SHOREWOOD (WILL IL) (APRSWXNET)   1149 PM DEC 20     41 MPH
2 E NEW MILLFORD (WINNEBAGO IL)  1130 PM DEC 20     41 MPH
2 NE BRADLEY (KANKAKEE IL) (APRSWXNET)1008 PM DEC 2041 MPH
2 SE LA SALLE (LA SALLE IL) (MESOWEST)531 PM DEC 20 41 MPH
PORTER COUNTY MUNICIPAL AIRPORT           113 PM DEC 20     41 MPH
OBSERVATIONS ARE COLLECTED FROM A VARIETY OF SOURCES WITH VARYING
EQUIPMENT AND EXPOSURES. NOT ALL DATA LISTED IS CONSIDERED OFFICIAL. THE
NATIONAL WEATHER SERVICE THANKS ITS PRIVATE AND PUBLIC PARTNERS FOR
PROVIDING US WITH THIS DATA.

$$

Meteorology

 

December 12th: 2pm-8pm Surface Map (Image is of Analyzed Temperatures, with 32° in Red)

Surface Weather Map

This loop shows the deep surface low's northeast path across the area. Such a path is generally not favorable for much snow in the area, and it was known and stressed for days that warm temperatures and high dew points ahead of the system would limit overall snowfall amounts.  Even after places transitioned to snow in the afternoon and early evening, their temperatures remained in the 32° to 35° range during the period of higher snowfall rates.  These mild readings, combined with a warm ground, helped in limiting snowfall efficiency and overall snowfall accumulations.  The rate of temperature drop in the evening had been forecast to be quicker, but even with incredibly strong northwest winds, the colder air actually wrapped to the west and south of the area first.  Note the strong packing of the isobars, a direct indication of significant forcing for winds.  The below image illustrates the strong pressure rises (~9mb/3hr) in the wake of the low pressure system that expanded across the area by early evening.

 

December 20th: 6 pm Analysis of 3-hr Pressure Change

Pressure Change

    Given the surface low path shown above, the upper levels of the atmosphere would be key for whether heavy snowfall rates would exist.  These combined with the winds gave forecasters concern that blizzard conditions would develop, at least at times, for a larger part of the area.  The below images depict key upper level features during the event, and explain why some of the heavier snowfall rates remained just to the northwest of the area.

700 mb

850 mb

700 mb Map

700 mb Facts

   Below is a Friday image from the GOES visible satellite channel, depicting the snow cover in the wake of the December 19th-20th low pressure system.

Visible Satellite Image


Service

 

Weather Story: December 17th

Winter Storm Watches: December 18th AM

Weather Story:  December 20th AM

Weather Story Hazards Map Weather Story


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