December Weather Summary - Record Warm and Record Wet for Parts of Central/SE IL

Overview

December was an active weather month for central and southeast Illinois, and resulted in record to near record warm temperatures and precipitation.  Many days featured spring-like conditions, and temperatures were more typical for March.  Arctic air remained locked up well to the north, as westerly to southwesterly flow prevailed across the Midwest.  Little to no snow fell over the region, setting a record for the least snowy December for some locations.  

Two significant weather events impacted the area. On the 23rd severe weather and locally heavy rainfall was observed as strong low pressure tracked across the Midwest.  On the 26th-28th, heavy rains brought significant flash flooding and river flooding to central and southern Illinois, and as colder air filtered in on the north side of the system, an ice storm affected northern portions of central Illinois on the 28th.  All of this activity produced monthly precipitation of 2 to 4 times normal.

Major Events

• December 23: A powerful storm system impacted the area, bringing near record warmth, strong winds, and a few strong to severe thunderstorms.  An intense 985 mb low pressure system tracked from eastern Kansas into Wisconsin by evening. This resulted in warm southerly winds producing temperatures in the lower 60s, and unusually high moisture levels.  Thunderstorms moved into central Illinois during the morning, and due to strong low level wind shear in the vicinity of the warm front, several of the cells began to rotate.  Scattered wind damage reports were received along and east of a Taylorville to Pontiac line.  Another line of storms developed in southern Illinois, with the northern part of this line producing scattered wind damage from Clay to Lawrence counties.  The low pressure center deepened to 979 mb as it entered Wisconsin during the evening, and a tight pressure gradient developed, causing winds to gust to 40 to 50 MPH across central Illinois. 
• December 26-28: A powerful winter storm impacted the central U.S. from December 26th through the 28th.  This produced a variety of weather hazards across central and southeast Illinois, including heavy rain/flooding, significant ice accumulations, and strong winds.  The system began to spread rain into the region from the southwest during the early morning hours on Saturday, December 26th, and steady rains continued across much of central and southeast Illinois into Saturday night.  By Sunday morning, widespread 2 to 5 inch totals were reported southeast of a Jacksonville to Rantoul line. This amount of rain falling on saturated soil from recent wet conditions produced widespread flash flooding and fast rises on creeks and streams.  After a lull in the rainfall for much of Sunday, another round of moisture moved in from the south on Sunday night, and continued into Monday afternoon.  Heavy rains of 1 to 3 inches were common across the entire area from this portion of the event, further aggravating existing flooding conditions. Many rivers across the area were expected to rise to major flood stage due to the heavy rainfall.  
  
  As Canadian high pressure moved north of the Great Lakes on Sunday night, northeast winds brought colder air into central Illinois. Temperatures fell to around the freezing mark north of Canton to Bloomington line. This allowed much of the steady rains late Sunday night and Monday morning to fall as freezing rain. Although ground temperatures were warm preventing much freezing on paved surfaces, significant ice accumulations of one tenth, to three tenths of an inch were reported on elevated surfaces, including trees. This amount of ice, combined with strong easterly winds which gusted up to 40 to 50 MPH, brought down many tree limbs and power lines. Due to the very wet soil conditions, numerous large trees were uprooted, damaging homes and taking down power lines and power poles.  Widespread power outages were reported in Galesburg, Peoria, Bloomington/Normal, and many smaller communities. 

December 23 Rainfall	December 26-28 Rainfall

Precipitation

Snowfall

Temperatures

Climate Data

The table below summarizes December liquid equivalent 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.
 

Sites in Top 10 Wettest Decembers:

• Lincoln: 3rd wettest with 6.81"
• Peoria: 2nd wettest with 6.31"
• Springfield: 3rd wettest with 6.56"
• Urbana: #1 wettest with 7.47"
• Normal: #3 wettest with 6.77"

Sites in Top 10 Warmest Decembers:

• Lincoln: #1 warmest with 40.2
• Peoria: 2nd warmest with 41.1
• Springfield: 2nd warmest with 42.4
• Urbana: 2nd warmest with 40.8
• Normal: #1 warmest with 39.1

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.

• Peoria -- Peoria International Airport
• Springfield -- Abraham Lincoln Capital Airport
• Lincoln -- Lincoln NWS office
• Champaign -- University of Illinois - Willard Airport
• Decatur -- Decatur Airport
• Lawrenceville -- Lawrenceville-Vincennes International Airport
• Mattoon -- Coles County Airport

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