709
FXUS63 KILX 151801
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
101 PM CDT WED APR 15 2026
KEY MESSAGES
- A 60-80% CHANCE OF SCATTERED THUNDERSTORMS EXISTS THROUGHOUT
THE DAY. THIS EVENING, ESPECIALLY AFTER 4 PM AND PRIMARILY
NORTH OF INTERSTATE 70, THERE IS A SLIGHT RISK (LEVEL 2 OUT OF
5) FOR SEVERE WEATHER.
- LATE FRIDAY EVENING, AREAS GENERALLY WEST OF INTERSTATE 57
FACE A SLIGHT RISK (LEVEL 2 OF 5) FOR ANOTHER ROUND OF SEVERE
WEATHER.
- SIGNIFICANTLY COOLER WEATHER RETURNS THIS WEEKEND.
THERE WILL BE A LOW (20-30%) CHANCE FOR FROST SATURDAY NIGHT
NORTH OF INTERSTATE 70, AND A HIGHER CHANCE AREA-WIDE SUNDAY
NIGHT.
DISCUSSION
ISSUED AT 313 AM CDT WED APR 15 2026
TWO PRIMARY AREAS OF CONVECTIVE ACTIVITY ARE VISIBLE ON THE
RADAR THIS MORNING. ONE AREA IS SITUATED ACROSS SOUTHEAST IOWA
AND NORTHERN ILLINOIS, NEAR THE MAIN SYNOPTIC FRONT. THE SECOND
AREA IS LIFTING ACROSS THE MISSOURI OZARKS. BOTH ARE FUELED BY A
LOW-LEVEL JET AND SHORTWAVE ENERGY EJECTING AHEAD OF THE MAIN
UPPER TROUGH, WHICH IS CURRENTLY MOVING ACROSS THE LEE OF THE
ROCKIES.
CONVECTIVE TOPS ARE NOTABLY WARMING OVER THE OZARKS AS THIS
SYSTEM ENCOUNTERS DRIER MID-LEVEL AIR, WEAKER INSTABILITY, AND
REDUCED SURFACE MOISTURE CONVERGENCE. AS THE SHORTWAVE/MCV
CONTINUES ITS NORTHEAST TRACK OUT OF THE OZARKS AND INTO THE
MID-MISSISSIPPI VALLEY LATER THIS MORNING, IT IS EXPECTED TO
INTERACT WITH OUTFLOW BOUNDARIES FROM DECAYING NORTHERN STORMS
THAT WILL HAVE DRIFTED SOUTH OF THE MAIN SYNOPTIC FRONT.
THE NET EFFECT WILL BE AN AREA OF RE-BLOSSOMING CONVECTION OVER
CENTRAL ILLINOIS THIS MORNING. WHILE A TENUOUS LOW-LEVEL JET
MAY SUSTAIN THIS ACTIVITY INTO THE EARLY AFTERNOON, THE SEVERE
THREAT REMAINS LOW DUE TO RELATIVELY POOR LAPSE RATES AND
SHALLOW CAPE PROFILES.
THUNDERSTORM ACTIVITY IS EXPECTED TO BRIEFLY LULL THIS
AFTERNOON AS THE SHORTWAVE/MCV DEPARTS AND SUBSIDENCE OCCURS,
LEAVING A SOMEWHAT WORKED-OVER WARM SECTOR. HOWEVER, THIS LULL
MAY BE SHORT-LIVED DUE TO QUICKLY INCREASING SYNOPTIC ASCENT
WITHIN A DIFLUENT ZONE AHEAD OF THE MAIN UPPER-LEVEL SHORTWAVE
MOVING INTO THE LOWER MISSOURI VALLEY.
CONDITIONS ARE EXPECTED TO BECOME MORE FAVORABLE FOR SEVERE
WEATHER, PARTICULARLY WEST OF INTERSTATE 55, WHERE CAPE PROFILES
WILL BECOME CHUBBIER AS MID-LEVEL LAPSE RATES STEEPEN AHEAD OF
THE MAIN UPPER-LEVEL SHORTWAVE AND NEAR A RESIDUAL ELEVATED
MIXED LAYER (EML).
WITH BETTER CAPE AND DEEP-LAYER SHEAR OF 30 KNOTS OR GREATER,
SUPERCELL AND MULTICELL CLUSTERS ARE POSSIBLE ACROSS WEST-
CENTRAL ILLINOIS. MODELED HODOGRAPHS FROM THE HREF MEAN SUGGEST
STRAIGHT OR N-SHAPED PROFILES, WHICH ARE MORE INDICATIVE OF
SPLITTING SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND
DAMAGING WINDS.
WHILE IT IS UNCERTAIN IF THESE STORMS WILL BE SURFACE-ROOTED OR
ELEVATED, AN INTENSIFYING LOW-LEVEL JET THIS EVENING WILL
INCREASE STORM RELATIVE HELICITY (SRH) AND RESULT IN A MORE
CURVED HODOGRAPH. THIS INTRODUCES A TORNADO THREAT IF STORMS
MANAGE TO BECOME SURFACE-ROOTED.
REGARDLESS OF STORM INITIATION/EVOLUTION FOR THE LATE AFTERNOON
THROUGH EARLY EVENING PERIOD, CAM OUTPUT BECOMES MORE
CONSISTENT BY TONIGHT THAT ADDITIONAL STORMS UPSTREAM WILL
CONGEAL AND GROW UPSCALE INTO A LINEAR MCS OVERTIME AS THE
EFFECTIVE SURFACE BOUNDARY SAGS SOUTHWARD INTO CENTRAL ILLINOIS.
IN ADDITION TO THE SEVERE WEATHER THREAT, THERE IS A LOW
POTENTIAL FOR LOCALIZED FLASH FLOODING, PARTICULARLY IF STORMS
REPEATEDLY TRACK OVER THE SAME AREA. THE LATEST HREF QPF LPMM
HIGHLIGHTS A NARROW AREA IN EAST-CENTRAL ILLINOIS THAT COULD SEE
3-5 INCHES OF RAIN THROUGH THURSDAY MORNING. THIS IS NOTABLE,
AS CURRENT 6-HOUR FLASH FLOOD GUIDANCE SUGGESTS THAT GENERAL
FLOODING ISSUES COULD ARISE AFTER 2.5-3 INCHES OF RAIN.
A BREAK FROM STORM ACTIVITY IS EXPECTED ACROSS THE ENTIRE
REGION ON THURSDAY, DRIVEN BY SYNOPTIC-SCALE SUBSIDENCE
FOLLOWING THE DEPARTURE OF THE UPPER TROUGH.
HOWEVER, THE THREAT OF THUNDERSTORMS RETURNS OVER THE WEEKEND,
SPECIFICALLY BEGINNING FRIDAY NIGHT AND LASTING INTO SATURDAY.
THIS RENEWED ACTIVITY IS TIED TO A COMPACT SHORTWAVE TROUGH
LIFTING ACROSS THE MID-MISSISSIPPI VALLEY, PRECEDING A MORE
ROBUST, PIVOTING TROUGH AND ITS ASSOCIATED COLD FRONT. DESPITE
THE FRONTAL PASSAGE OCCURRING DURING A DIURNALLY UNFAVORABLE
TIME, THE PARAMETER SPACE FOR CAPE AND SHEAR APPEARS
SUFFICIENTLY VOLATILE TO SUPPORT AN ORGANIZED RISK OF SEVERE
WEATHER WHICH LASTS THROUGH THE OVERNIGHT HOURS AS THE
CONVECTION GROWS UPSCALE ALONG THE FRONT.
A SIGNIFICANT COOLING TREND IS EXPECTED FROM SATURDAY NIGHT
THROUGH MONDAY FOLLOWING THE PASSAGE OF THE COLD FRONT, AS THE
PREVIOUS WEEK'S WARM, MOIST AIR MASS IS DISPLACED. LATEST NBM
GUIDANCE INDICATES A CONCERN FOR WIDESPREAD FROST, WITH LOW
TEMPERATURES SATURDAY AND SUNDAY NIGHT ANTICIPATED TO FALL INTO
THE 30S.
BY THE MIDDLE OF NEXT WEEK, TEMPERATURES ARE FORECAST TO
QUICKLY REBOUND INTO THE LOWER 70S. THIS WARMING TREND IS DUE TO
AN UPPER-LEVEL PATTERN EXHIBITING SOME BLOCKINESS, ALLOWING AN
AMPLIFIED RIDGE AXIS TO BUILD INTO THE REGION.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 101 PM CDT WED APR 15 2026
MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS WILL PUSH ACROSS THE
CENTRAL ILLINOIS TERMINALS THROUGH THE TAF PERIOD. CONFIDENCE IN
TIMING AND COVERAGE OF STORMS REMAINS LOW, RESULTING IN SEVERAL
PERIODS OF EITHER TEMPO OR PROB30 FOR TSRA THROUGH TONIGHT. AWAY
FROM STORMS, VFR CONDITIONS ARE EXPECTED. SOUTHWEST WINDS WILL
CONTINUE THROUGH THE PERIOD, GUSTING TO 25 KT AT TIMES, SHIFTING TO
THE WEST THURSDAY MORNING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...NMA
AVIATION...NMA
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