December Weather Summary

December 2013 saw a quick start to winter for central and southeast Illinois.  Several bouts of Arctic air affected the region, and with this cold air in place a few significant winter weather events occurred:  

  • The first major event of the season was Dec. 5-6, as low pressure tracked near the Ohio Valley.  This system spread a band of heavy snow across southern Illinois, where 5-11" totals were common south of I-70.  Amounts quickly tapered off to the north, with much of central IL receiving no snow.
     
  • About a week later another snow system affected the region, this time targeting areas a bit farther north.  Low pressure tracking east from the Plains spread moisture north into a cold airmass over the central part of the state.  This was a rather slow moving system which allowed a prolonged period of snow to fall from the afternoon of Friday, Dec. 13, into Saturday afternoon.  Snow totals from this event were generally 4 to 6 inches north of I-70, with a couple concentrated areas of heavier 8-9 inch amounts in west-central, and east-central Illinois.
     
  • The most intense storm system of the month moved through a week later, on Dec. 20-21.  Low pressure tracked from Texas northeast into Indiana, spreading unseasonably high moisture levels north into the Midwest.  Southerly flow also brought much warmer air north.  This setup allowed heavy rain to fall over eastern IL, where 1 to 3 inch totals were common.  South of I-70 a few rain totals as high as 3.50 inches were reported!  Due to the heavy rain falling in conjunction with recent snowmelt, many streams and rivers rose above flood stage in the following days.  Farther northwest, a shallow layer of cold air near the surface, with much warmer air aloft, caused freezing rain to form.  Between one tenth and one quarter inch of ice was reported west of I-55.  As this system pulled away, a deeper layer of cold air moved in from the west allowing 1-2 inches of snow to fall west of the Illinois River.

Dec. 5-6 Snowfall 

Dec. 13-14 Snowfall 

Dec. 20-21 Rainfall 

Dec. 5-6 Snowfall 

Dec. 13-14 Snowfall 

Dec. 20-21 Rainfall 


Daily mean temperatures were 2-5 degrees below normal for the month overall.  After a mild first few days of December, the first Arctic airmass moved in on the 5th, and lingered into the middle of the month.  Temperatures during this stretch were 10-15 degrees below normal.  Some temperature moderation occurred during the last half of the month, though a few short-lived Arctic intrusions brought bitter cold back to the region.  Morning lows dropped below zero across the northern portions of central IL on the 30th, along with wind chills of -10 to -20. 

Liquid-equivalent precipitation was below normal for much of the area, except for southeast IL which saw as much as 150% of normal.  Monthly snowfall was a few inches above normal, again except for southeast IL which was nearly half a foot above normal.

 

December Temperature Departure from Normal 

December Precipitation Total 

 December Snowfall Total

 Dec. Temp. Departure from normal

Dec. Precip. Total

Dec. Snowfall Total 


The table below summarizes December 2013 precipitation, snowfall, and temperature, and departure from normal for selected cities across central and southeast Illinois.  Data from Peoria and Springfield are from ASOS sites, while others are from NWS Cooperative Observers.
 

Site Precipitation Departure from Normal Snowfall Departure from Normal Average Temperature Departure from Normal
Charleston

2.86"

 -0.29" 4.0" +1.4" 31.5 -0.6
Decatur

1.97"

 -0.81 7.2"  +2.3"  27.6  -3.6 
Galesburg

1.13" 

-1.14"  9.5"  +3.6"  21.0  -5.0 
Jacksonville

1.37" 

-1.37"  4.2"  -1.0"  27.3  -3.1 
Lincoln

1.51" 

-1.13"  6.4"  +0.2"  25.8  -3.7 

Normal

1.66" 

-1.04"  9.0"  +3.9"  25.3  -2.5 
Olney

5.43" 

+1.55"  10.0"  +7.1"  30.1  -2.6 
Peoria

1.49" 

-0.93"  8.5"  +1.4"  24.6  -4.0 
Springfield

1.60" 

-0.92"  5.6"  +2.6"  27.2  -3.2 
Urbana  M  M  M  M  M


Links below are the monthly climate summaries for area cities. Only the summaries for Peoria, Springfield and Lincoln are considered "official", meaning they are the station of record for their respective locations. The other summaries are "supplemental", meaning another location in the area is the official climate station for that city.

Climate data for other area cities is available at http://www.nws.noaa.gov/climate/xmacis.php?wfo=ilx



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