075
FXUS63 KILX 161057
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
557 AM CDT THU APR 16 2026
KEY MESSAGES
- THERE IS CURRENTLY AN ENHANCED RISK (LEVEL 3 OF 5) FOR AREAS
NEAR AND WEST OF THE ILLINOIS RIVER ON FRIDAY WHERE A
SIGNIFICANT, ALL-HAZARDS SEVERE WEATHER OUTBREAK LOOMS.
- MUCH COOLER TEMPERATURES RETURN THIS WEEKEND, WITH AN
ATTENDANT FROST RISK BOTH SATURDAY NIGHT AND SUNDAY NIGHT.
DISCUSSION
ISSUED AT 355 AM CDT THU APR 16 2026
A MID-LEVEL SHORTWAVE TROUGH IS CURRENTLY SITUATED OVER EAST-
CENTRAL IOWA, VISIBLE ON EARLY MORNING WATER VAPOR IMAGERY. A
SIGNIFICANT PLUME OF MOISTURE EXTENDS FROM CENTRAL ARKANSAS INTO
THE LOWER GREAT LAKES, COINCIDING WITH AN AREA OF MOSTLY
STRATIFORM RAIN. OCCASIONAL CONVECTIVE ACTIVITY, INDICATED BY
COOLING CLOUD TOPS AND 40 DBZ RADAR ECHOES, IS EMBEDDED WITHIN
THIS RAIN SHIELD. THIS ACTIVITY IS EXPECTED TO MOVE SLOWLY
EASTWARD AND EXIT ILLINOIS SHORTLY AFTER SUNRISE AS THE UPPER
TROUGH PROGRESSES INTO NORTH-CENTRAL ILLINOIS AND THE LOW-LEVEL
JET WEAKENS.
SYNOPTIC-SCALE SUBSIDENCE AND INCREASING HEIGHT TENDENCIES WILL
BUILD ACROSS CENTRAL ILLINOIS BY MIDDAY, EFFECTIVELY ENDING
PRECIPITATION CHANCES FOR MOST, IF NOT ALL, OF THE FORECAST
AREA. WITH CLOUDS LIFTING AND BREAKING BEHIND THE DEPARTING
SHORTWAVE, TEMPERATURES WILL WARM INTO THE MID-TO-UPPER 70S.
WHILE THE PRIMARY FORECAST CALLS FOR A CLEAR DAY WITHOUT
FURTHER CONVECTION, A SLIGHT CHANCE OF ISOLATED STORMS EXISTS
NEAR AND SOUTH OF INTERSTATE 70 LATE THIS AFTERNOON. THIS IS
ASSOCIATED WITH A SEPARATE, TRAILING MID-LEVEL SHORTWAVE
WOBBLING ACROSS THE EASTERN OZARKS AND INTO FAR SOUTHERN
ILLINOIS. IN THIS AREA, THERMODYNAMIC PROFILES BECOME MORE
FAVORABLE, WITH STEEPENING MID-LEVEL LAPSE RATES BOOSTING MLCAPE
VALUES INTO THE 1000-2000 J/KG RANGE.
HOWEVER, THE POTENTIAL FOR WIDESPREAD, VIGOROUS CONVECTIVE
DEVELOPMENT IS LIMITED BY FLEETING KINEMATICS. AS THE UPPER JET
CORE CONTINUES ITS EASTWARD DEPARTURE, DEEP LAYER SHEAR AROUND
THE TIME OF POTENTIAL INITIATION IS ONLY FORECAST TO BE ABOUT
20-25 KTS. CONSEQUENTLY, PORTIONS OF SOUTHERN ILLINOIS ARE
OUTLOOKED FOR GENERAL THUNDERSTORMS TODAY, BUT NOT FOR SEVERE
THUNDERSTORMS.
WIDESPREAD THUNDERSTORM ACTIVITY IS FORECAST TO RETURN FRIDAY.
THIS DEVELOPMENT IS ASSOCIATED WITH SUBTLE SHORTWAVE ENERGY
EJECTING FROM THE CENTRAL PLAINS TOWARD THE MID-MISSISSIPPI
VALLEY, OCCURRING AHEAD OF A MORE POTENT TROUGH PIVOTING ACROSS
THE NORTH-CENTRAL U.S.
A HIGHLY VOLATILE ENVIRONMENT IS EXPECTED TO EVOLVE BY FRIDAY
AFTERNOON. THE ADVECTION OF AN ELEVATED MIXED LAYER (EML) AHEAD
OF A COLD FRONT WILL CONTRIBUTE TO INCREASING MID-LEVEL LAPSE
RATES AND OVERALL BUOYANCY, WITH MLCAPE AROUND 2500 J/KG.
THERE IS SOME UNCERTAINTY REGARDING THE INITIAL STORM MODE.
SOME 00Z CAMS INDICATED THE POTENTIAL FOR ISOLATED SUPERCELLS
TO DEVELOP WELL AHEAD OF THE COLD FRONT, PRIMARILY OVER
SOUTHEAST IOWA AND FAR WEST-CENTRAL ILLINOIS LATE IN THE
AFTERNOON. THIS ACTIVITY WOULD BE TRIGGERED BY THE SUBTLE
SHORTWAVE ENERGY AND OCCUR NEAR A DIFFUSE DEWPOINT GRADIENT OR
PSEUDO WARM FRONT. IF SUCH ISOLATED ACTIVITY DEVELOPS JUXTAPOSED
WITH AN INCREASING KINEMATIC FIELD (BULK SHEAR OF 35 KTS),
AN ALL-HAZARDS RISK COULD ENSUE AHEAD OF THE MAIN COLD FRONT.
THIS IS NOT THE MOST LIKELY SCENARIO.
IT'S IMPORTANT TO NOTE THAT THE MAIN AREA OF CONVECTIVE
INITIATION IS EXPECTED TO OCCUR WELL TO OUR WEST ALONG THE COLD
FRONT. AND, WITH THE ORIENTATION OF THE DEEP-SHEAR VECTORS
BECOMING PARALLEL TO THE MAIN FORCING, SUPERCELLS THAT DEVELOP
ON THE COLD FRONT ARE ANTICIPATED TO GRADUALLY GROW UPSCALE INTO
A LINEAR MCS, WHICH WOULD ENTER OUR AREA LATER IN THE EVENING.
AS THE LINEAR MCS MOVES INTO WEST-CENTRAL ILLINOIS, A CONTINUED
RISK FOR SEVERE WEATHER IS ANTICIPATED, LASTING WELL INTO THE
OVERNIGHT HOURS. RESIDUAL SUPERCELL STRUCTURES MAY PERSIST
INITIALLY, DRIVEN BY AN INCREASING LOW- LEVEL JET THAT ELONGATES
THE LOW-LEVEL HODOGRAPH AND ENHANCES 0-3 KM SRH. HOWEVER,
CONSOLIDATING COLD POOLS AMID STRONG LOW-LEVEL CAPE AND SHEAR,
IS EXPECTED TO SUPPORT A TRANSITION TO A MATURE QLCS. THIS
MATURE QLCS WILL LIKELY FEATURE EMBEDDED BOWING SEGMENTS AND
MESOVORTICIES THAT POSE A SUBSTANTIAL RISK FOR STRAIGHT- LINE
WIND DAMAGE AND BRIEF TORNADOES AS IT PROGRESSES EASTWARD.
A SIGNIFICANT COOLING TREND IS FORECAST TO BEGIN BY SATURDAY AS
THE COLD FRONT MOVES THROUGH AND DISPLACES THE WARM, MOIST AIR
MASS FROM THE PREVIOUS WEEK. TEMPERATURES ARE EXPECTED TO
EXHIBIT A NON-DIURNAL TREND, WITH HIGHS LIKELY OCCURRING EARLIER
IN THE DAY. THE LATEST NBM GUIDANCE RAISES CONCERN FOR
WIDESPREAD FROST, WITH LOW TEMPERATURES ANTICIPATED TO FALL INTO
THE 30S SATURDAY AND SUNDAY NIGHTS.
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 /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 524 AM CDT THU APR 16 2026
LOW-LEVEL CLOUDS WILL LIFT AND BREAK FOR SUN PRIOR TO 18Z
BEHIND A DEPARTING DISTURBANCE. VFR CONDITIONS WILL THEN
DOMINATE THE REMAINDER OF THIS TAF CYCLE. BREEZY WEST WINDS WILL
DIMINISH BY SUNSET, BECOMING LIGHT AND VARIABLE OVERNIGHT INTO
FRIDAY.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...MJA
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