A cold front triggered scattered thunderstorms across central Illinois during the late afternoon and evening of May 20th. Many of the storms dropped dime to quarter-sized hail, while a couple cells produced damaging downburst winds.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS ILX wrote it up.
A cold front triggered scattered thunderstorms across central Illinois during the late afternoon and evening of May 20th. Many of the storms dropped dime to quarter-sized hail, while a couple cells produced damaging downburst winds. In addition, isolated, slow moving thunderstorms developed along the I-57 corridor. One of these thunderstorms produced very heavy rain and flash flooding in Effingham County.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Lincoln, IL wrote its last area forecast discussion before the first event at May 20, 1:35 PM CST, 2 hours earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 235 PM CDT SUN MAY 20 2012 .DISCUSSION... ISSUED 235 PM CDT SUN MAY 20 2012 LATEST SURFACE ANALYSIS HAD AN AREA OF LOW PRESSURE CENTERED OVER NORTH CENTRAL WISCONSIN/EXTREME WESTERN UPPER MICHIGAN...WITH AN ASSOCIATED COLD FRONT EXTENDING SOUTH SOUTHWEST THROUGH IOWA AND MISSOURI INTO THE SOUTHERN PLAINS. THE PASSAGE OF THIS COLD FRONT TONIGHT SHOULD BRING SCATTERED SHOWERS AND THUNDERSTORMS TO THE FORECAST AREA TONIGHT...VERY POSSIBLY THE ONLY RAINFALL FOR AT LEAST THE NEXT WEEK. ASIDE FROM PRECIPITATION CHANCES/TIMING TONIGHT...PRIMARY FORECAST CONCERN TODAY IN THIS RATHER QUIET WEATHER PERIOD REVOLVES AROUND TEMPERATURES. 12Z MODELS IN REASONABLE AGREEMENT OVER THE NEXT FEW DAYS IN THE PREDOMINANTLY BENIGN WEATHER PERIOD EXPECTED. HOWEVER... MODEL/ENSEMBLE SPREAD INCREASES SIGNIFICANTLY BY THE END OF THE WEEK...AND RUN-TO-RUN CONSISTENCY HAS BEEN POOR. THE DISAGREEMENT LOCALLY REVOLVES AROUND HOW STRONG THE EASTERN U.S. RIDGE WILL BE AND IF A STRONG ENOUGH IMPULSE FLATTENS TO THE TOP OF THE RIDGE TO DROP A FRONTAL BOUNDARY INTO THE FORECAST AREA. FOR NOW... PRIMARILY TO MINIMIZE FORECAST FLIP-FLOP...HAVE LEANED TOWARD THE STRONGER RIDGE/DRIER SOLUTION OF THE ECMWF. HOWEVER...EVEN THE ECMWF IS LITTLE WEAKER WITH THE RIDGE FOR FRIDAY/SATURDAY THAN IT HAS BEEN. SO...THE LATE WEEK FORECAST IS CERTAINLY SUBJECT TO CHANGE. SHORT TERM...TONIGHT THROUGH WEDNESDAY...THE UPSTREAM COLD FRONT WILL CLEAR THE FORECAST AREA TONIGHT. MUCH AS ANTICIPATED THE PAST FEW DAYS...PRE FRONTAL SURFACE BASED CAPE VALUES HAVE CLIMBED INTO THE 1500-2000 J/KG RANGE...BUT DEEP LAYER SHEAR IS ONLY ON THE ORDER OF 25 KTS. THE CONVERGENCE ALONG THE COLD FRONT IS ALSO RATHER WEAK. FOR THESE REASONS...STILL DO NOT EXPECT ORGANIZED SEVERE WEATHER. HOWEVER...A FEW PULSE SEVERE STORMS WITH DAMAGING WINDS AND LARGE HAIL CAN NOT BE RULED OUT GIVEN THE INSTABILITY AND VERY STEEP LOW LEVEL LAPSE RATES. THE MOST INTENSE STORMS SHOULD FADE BY EARLY EVENING AS DIURNAL INSTABILITY WANES. MUCH COOLER...BUT CLOSER TO NORMAL...TEMPERATURES ARE ANTICIPATED IN THE WAKE OF THE COLD FRONT FOR TOMORROW. THIS COOL DOWN WILL BE SHORT LIVE HOWEVER AS AN AREA OF HIGH PRESSURE MOVES ACROSS THE AREA AND SOUTHERLY FLOW RETURNS BY TUESDAY NIGHT. THIS WILL RESULT IN WARMING...BUT STILL QUIET WEATHER FOR THE REST OF THE PERIOD. LONG TERM...THURSDAY THROUGH SUNDAY...SOUTHERLY LOW LEVEL FLOW AND BUILDING UPPER HEIGHTS SUPPORT MOSTLY QUIET AND INCREASINGLY WARM WEATHER THROUGH THE EXTENDED RANGE OF THE FORECAST. AS MENTIONED IN THE MODEL DISCUSSION ABOVE...STILL NEED TO KEEP AN EYE ON HOW FAR SOUTH A MOSTLY EAST/WEST ORIENTED FRONTAL BOUNDARY TO OUR NORTH WILL SINK AS DISTURBANCES TOP THE RIDGE. IF MODELS TREND ANY FURTHER SOUTH WITH THE FRONT...WE WILL NEED TO INTRODUCE POPS TO AT LEAST NORTHERN SECTIONS OF THE FORECAST AREA AND CUT TEMPERATURES A BIT. BAK && .AVIATION... ISSUED 1245 PM CDT SUN MAY 20 2012 GREAT AMOUNT OF MODEL VARIANCE IN THE FACE OF BLOSSOMING CU FIELD OVER ILX TERMINALS. SWRLY WINDS BECOMING BLUSTERY...WITH GUSTS 25-30KTS. SOME MINOR RETURNS POPPING UP ON RADAR...BUT WIDESPREAD EFFECTIVE CONVECTION HOLDING A BIT. PLENTY OF INSTABILITY OUT THERE...BUT LIMITED MOISTURE. STILL CONCERNED ABOUT EXTENT OF AFTERNOON CONVECTION...BUT WANT MORE THAN VCTS IN THE TAFS. HAVE PLACED TEMPOS FOR BEST CHANCES OF TS IN PIA AND BMI...AND RA FOR SPI AND CMI. WILL LIKELY BE A LAST MINUTE CALL WITH SCT TS THIS EVENING. BEHIND THE FRONT...NWRLY WINDS AND THEN A QUESTION OF HOW QUICKLY THE MVFR CIGS CONTINUE. ONCE AGAIN...LIMITED MOISTURE IS A CONCERN...WITH MAJORITY OF MVFR CIGS MOVING WELL NORTH...CLOSER TO THE LOW. HJS && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LINCOLN IL 309 PM CDT SUN MAY 20 2012 ILZ027>031-036>038-040>042-047-048-211100- CASS-FULTON-KNOX-LOGAN-MARSHALL-MASON-MCLEAN-MENARD-PEORIA- SCHUYLER-STARK-TAZEWELL-WOODFORD- 309 PM CDT SUN MAY 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS. .DAY ONE...TONIGHT A COLD FRONT APPROACHING FROM THE WEST WILL BRING SCATTERED THUNDERSTORMS TO PARTS OF CENTRAL ILLINOIS THIS AFTERNOON INTO EARLY THIS EVENING. THERE IS A SLIGHT RISK THAT A FEW OF THE THUNDERSTORMS FROM MID AFTERNOON THROUGH EARLY THIS EVENING MAY BECOME SEVERE...CONTAINING GUSTY WINDS AND LARGE HAIL BEFORE THE STORMS WEAKEN AFTER SUNSET. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE REQUIRED FROM MID AFTERNOON THROUGH EARLY THIS EVENING. THE PRIMARY TIME FRAME FOR THUNDERSTORMS AND POSSIBLE SPOTTER ACTIVATION TODAY WOULD BE FROM 300 PM UNTIL 700 PM THIS EVENING. ILZ043>046-049>057-061>063-066>068-071>073-211100- CHAMPAIGN-CHRISTIAN-CLARK-CLAY-COLES-CRAWFORD-CUMBERLAND-DE WITT- DOUGLAS-EDGAR-EFFINGHAM-JASPER-LAWRENCE-MACON-MORGAN-MOULTRIE- PIATT-RICHLAND-SANGAMON-SCOTT-SHELBY-VERMILION- 309 PM CDT SUN MAY 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS...EAST CENTRAL ILLINOIS AND SOUTHEAST ILLINOIS. .DAY ONE...TONIGHT A COLD FRONT APPROACHING FROM THE WEST LATE TODAY WILL BRING SCATTERED THUNDERSTORMS TO PARTS OF CENTRAL ILLINOIS THIS AFTERNOON INTO EARLY THIS EVENING. ALTHOUGH NO ORGANIZED SEVERE WEATHER IS ANTICIPATED AT THIS TIME...A FEW OF THE THUNDERSTORMS FROM LATE THIS AFTERNOON THROUGH THIS EVENING MAY CONTAIN GUSTY WINDS AND HAIL BEFORE THE STORMS WEAKEN AFTER SUNSET. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. HJS
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LINCOLN IL
431 PM CDT SUN MAY 20 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0428 PM HAIL TRIVOLI 40.69N 89.88W
05/20/2012 M0.50 INCH PEORIA IL LAW ENFORCEMENT
&&
TIMTEThe Lincoln radar (KILX), 56 km away, was scanning. The volume nearest the first event began at 21:35 UTC.
8 hail, 5 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Several trees were blown down. The front of a garage was pulled out, and the roof was torn off an outbuilding.
Rural areas of central Effingham County accumulated nearly 4.00 of rain in two hours during the early evening of May 20th. An isolated, slow moving thunderstorm was responsible for the heavy rainfall. Many rural roads south of I-70 and west of I-57, between Altamont and Watson, were inundated.
Power lines were blown down west of Sherman.
A tree fell onto a vacant house in Williamsville.
A power pole was blown down and two trees were damaged in Elkhart.
A few trees were blown down and roofing was torn off a home.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2012Every state in 2012This day in weather historyWarnings in Illinois, May 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 374470, 387112, 374473, 374471, 374472, 374462, 374463, 374464, 374465, 374466, 374467, 374474, 374468, 374469.