329
FXUS63 KILX 172322
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
622 PM CDT FRI APR 17 2026
KEY MESSAGES
- AN INTENSE, MULTI-HAZARD SEVERE THUNDERSTORM EVENT APPEARS
LIKELY THIS EVENING INTO TONIGHT. AREAS ALONG AND WEST OF A
TAYLORVILLE TO CHAMPAIGN LINE ARE IN AN ENHANCED RISK (LEVEL 3
OF 5) OF SEVERE STORMS, WHILE AREAS TO THE EAST ARE IN A
SLIGHT RISK (LEVEL 2 OF 5). STORMS ARE LIKELY TO IMPACT AREAS
WEST OF I-55 BETWEEN 5-9 PM, THEN SPREAD EAST OF I-55 LATE
THIS EVENING.
- THE STORMS COULD PRODUCE LOCALLY HEAVY RAINFALL OF 2-4".
SCATTERED INSTANCES OF FLOODING ARE POSSIBLE, ESPECIALLY IN
URBAN, LOW- LYING, OR OTHER POOR DRAINAGE AREAS. A FLOOD WATCH
HAS BEEN ISSUED FOR AREAS ALONG AND NORTH OF SHELBY TO EDGAR
COUNTY.
- COOLER AIR RETURNS THIS WEEKEND, AND LOWS IN THE 30S MAY
RESULT IN FROST DEVELOPMENT BOTH SATURDAY NIGHT AND SUNDAY
NIGHT.
DISCUSSION
ISSUED AT 134 PM CDT FRI APR 17 2026
*** SEVERE STORMS LIKELY THIS EVENING-TONIGHT ***
THE 'BOTTOM LINE UP FRONT': THE FORECAST LARGELY REMAINS ON
TRACK, WITH AN INTENSE, MULTI-HAZARD SEVERE THUNDERSTOM EVENT
THIS EVENING INTO TONIGHT.
SFC LOW IS POSITIONED JUST NORTH OF DULUTH, MN AS OF 18Z/1PM,
WITH THE ATTENDANT COLD FRONT EXTENDING SOUTH NEAR MINNEAPOLIS,
MN, TO DES MOINES, IA, TO WICHITA KS. IN THE LAST HOUR, STORMS
HAVE ERUPTED ACROSS EASTERN IA ALONG A PRE-FRONTAL TROUGH, WHICH
EXTENDS ROUGHLY FROM THE IA/WI BORDER TO NEAR KIRKSVILLE, MO.
THIS IS AN EVOLUTION THAT CAMS HIGHLIGHTED IN RECENT DAYS. LOCALLY,
TEMPS HAVE PUSHED TO NEAR 80F WHILE DEWPOINTS ARE STILL IN THE
MID 60S. CONTINUED ADVECTION OF THE EML AND DEEPER MOISTURE
CONTENT HAVE LED TO INSTABILITY RISING OVER 2000 J/KG, AND PWATS
OVER 1.2". VIS SATELLITE SHOWS A CU FIELD QUICKLY EXPANDING
ACROSS THE ILX CWA, AND ANY CAPPING IS WEAK OR NON- EXISTENT.
STILL, THE BEST SOURCE OF FORCING IN THE SHORT-TERM WILL BE THAT
PRE-FRONTAL TROUGH NOTED TO OUR NORTH/WEST. FOR OUR AREA,
ISOLATED SUPERCELLS CANNOT BE RULED OUT THIS AFTERNOON, AND ANY
MATURE STORMS THAT DEVELOP WILL POSE A RISK OF ALL SEVERE
HAZARDS.
THE MORE WIDESPREAD SEVERE THREAT IS EXPECTED TO COME AS THE
COLD FRONT APPROACHES AND UPSCALE GROWTH OF THUNDERSTORMS
OCCURS. AS THESE STORMS MOVE INTO IL, A HIGHLY UNSTABLE AIRMASS
WILL STILL BE IN PLACE, WITH INCREASING LOW-LEVEL SHEAR AS THE
LLJ RAMPS UP AFTER 00Z/7PM. THIS LINE OF STORMS COULD PRODUCE
SCATTERED DAMAGING WINDS, WITH GUSTS OVER 75 MPH POSSIBLE. LINE-
EMBEDDED TORNADOES REMAIN A CONCERN, AS 0-1KM SRH VALUES SURGE
ABOVE 150 J/KG IN RESPONSE TO THE LLJ.
CAM TIMING HAS NOT CHANGED MUCH FROM PREVIOUS ITERATIONS,
ALTHOUGH THERE IS SOME THOUGHT THAT COLD POOL DOMINANT STORM
STRUCTURES MAY SURGE EAST A SMIDGE FASTER THAN CAMS CURRENTLY
SUGGEST. OUR LATEST THINKING IS THAT THE LINE WILL IMPACT AREAS
WEST OF I-55 BETWEEN 5-8 PM, THEN CONTINUE EAST AND REACH
PORTIONS OF THE I-57 CORRIDOR BY 9- 10 PM. THE MAIN LINE OF
STORMS SHOULD REACH THE IL/IN BORDER BY ABOUT 05Z/MIDNIGHT CT.
SCATTERED SHOWERS MAY LINGER FOR A FEW HOURS BEHIND THE MAIN
LINE OF SEVERE STORMS.
*** FLOODING POTENTIAL ***
IN LIGHT OF RECENT RAINS AND UNSEASONABLE PWATS (95TH+
PERCENTILE) PRESENT WITH THIS SYSTEM, CONCERN IS GROWING THAT
AT LEAST SCATTERED FLASH FLOODING WILL OCCUR WITH TONIGHT'S
STORMS. DESPITE THE RELATIVELY PROGRESSIVE FORWARD MOTION OF THE
LINE, THE LAST FEW CYCLES OF HREF LPMM GUIDANCE HAVE
CONSISTENTLY HIGHLIGHTED AN AREA ROUGHLY FROM THE IL RIVER TO
THE I-72/DANVILLE CORRIDOR WHERE LOCALIZED RAINFALL AMOUNTS OF
2-4" ARE POSSIBLE. 3-HR FLASH FLOOD GUIDANCE IS LESS THAN 2" IN
MOST LOCATIONS, AND A RECENT MESOSCALE PRECIPITATION DISCUSSION
FROM WPC NOTES STORMS WILL BE HIGHLY EFFICIENT RAINFALL
PRODUCERS WITH RATES OF 1-2" PER HOUR. A FLOOD WATCH WAS ISSUED
TO CAPTURE THE COUNTIES WHERE SCATTERED INSTANCES OF FLOODING
SEEM MOST LIKELY TO ARISE.
*** REST OF THE WEEKEND ***
FOLLOWING TONIGHT'S FROPA, BREEZY NORTHWEST WINDS WILL PERSIST
INTO SAT. HIGHS ARE LIKELY TO BE COOLER OVER THE WEEKEND, IN
THE 50S OR LOW 60S. NO MAJOR CHANGES TO THE FROST/FREEZE OUTLOOK
FOR SATURDAY NIGHT AND SUNDAY NIGHT. FROST CHANCES COULD EXTEND
AS FAR SOUTH AS I- 70 BOTH NIGHTS, BUT THE CHANCES FOR FROST
GENERALLY INCREASE WITH NORTHWARD EXTENT. THE GRIDDED FORECAST
REFLECTS THIS. WHILE SOME SPOTS, PARTICULAR THOSE IN LOW-LYING
AREAS, COULD DROP BELOW 32F, A WIDESPREAD FREEZE APPEARS
UNLIKELY.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 620 PM CDT FRI APR 17 2026
LINE OF TSRA PRESENT ALONG THE IL/IA BORDER AS OF 2315Z, MOVING
WEST IN TIME, WITH SCATTERED TSRA AHEAD OF THE LINE. MAIN
CONCERN FOR THIS TAF PERIOD WILL BE TIMING OUT THE STORMS,
WHICH COULD BRING SEVERE WIND GUSTS AND LARGE HAIL. BASED ON
RADAR TRENDS, SLOWED THE TIMING BY AN HOUR OR TWO AT EACH
TERMINAL. STORMS SHOULD BE PAST CMI BY 06Z. THESE STORMS ARE
ASSOCIATED WITH A FRONT WHICH WILL SWING WINDS TO NORTHWESTERLY
AND A BRIEF PERIOD OF MVFR CEILINGS ALONG/BEHIND THE FRONT.
WINDS WILL REMAIN GUSTY INTO SATURDAY, WHILE CEILINGS IMPROVE
AND SKIES CLEAR INTO THE DAY.
ILX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH UNTIL 4 AM CDT SATURDAY FOR ILZ027>031-036>038-
040>057-061.
KEY MESSAGES...ERWIN
DISCUSSION...ERWIN
AVIATION...ERWIN
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