954
FXUS63 KILX 161023 CCA
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
356 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 LATER 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 25
KTS. CONSEQUENTLY, PORTIONS OF SOUTHERN ILLINOIS ARE OUTLOOKED
FOR GENERAL THUNDERSTORMS TODAY, BUT NOT FOR SEVERE
THUNDERSTORMS.
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.
SEVERAL 00Z CAMS INDICATE 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),
THERE WOULD BE A CONCERN FOR AN ISOLATED, ALL-HAZARDS SUPERCELL
RISK AHEAD OF THE MAIN COLD FRONT.
IF RESIDUAL CAPPING PRECLUDES PRE-FRONTAL CONVECTION ACROSS OUR
AREA DURING THE LATE AFTERNOON AND EARLY EVENING HOURS, THEN
OUR STORM TIMING AND STORM MODE AND STORM RISKS WILL LOOK A LITTLE
DIFFERENT. IT'S IMPORTANT TO NOTE THAT THE MAIN AREA OF CONVECTIVE
INITIATION IS EXPECTED TO OCCUR WELL TO OUR WEST DURING THE LATE
AFTERNOON ALONG THE COLD FRONT. BUT, 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 AS THEY ENTER OUR AREA LATER IN THE
EVENING.
AS THE LINEAR MCS MOVES INTO WEST-CENTRAL ILLINOIS LATER IN THE
EVENING, 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, THE CONSOLIDATING COLD POOL, AMIDST 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 MESOVORTICES THAT MAINTAIN A SUBSTANTIAL
RISK FOR STRAIGHT-LINE WINDS 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 /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1217 AM CDT THU APR 16 2026
AREA OF RAIN WILL EXIT THE EASTERN TERMINALS OVER THE NEXT HOUR
OR SO. THERE IS A LOW (20-40% CHANCE) THAT MVFR STRATOCU WILL
DEVELOP NEAR/AFTER DAYBREAK, OTHERWISE CONDITIONS WILL BE VFR
THROUGH THE FORECAST. SOUTHWEST WINDS WILL REMAIN GUSTY NEAR 25
KT UNTIL LATE AFTERNOON, THEN GO LIGHT AS SURFACE RIDGING
BUILDS IN.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...25
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page