253
FXUS63 KILX 161121
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
621 AM CDT SAT MAY 16 2026
KEY MESSAGES
- PERIODS OF THUNDERSTORMS WILL TRACK ACROSS CENTRAL ILLINOIS
TODAY, BRINGING A MARGINAL RISK (LEVEL 1 OF 5) FOR 60 MPH
WIND GUSTS AND GOLF BALL-SIZED HAIL.
- SLOW-MOVING STORMS WILL BRING A RISK OF LOCALIZED FLOODING
TODAY, PRODUCING ISOLATED RAINFALL TOTALS OF 3 TO 4 INCHES IN
EAST-CENTRAL OR SOUTHEAST ILLINOIS.
- A SEPARATE, MUCH STRONGER STORM SYSTEM WILL BRING A THREAT OF
ORGANIZED, HIGH-IMPACT SEVERE WEATHER TO THE AREA IN THE
MONDAY-TUESDAY TIMEFRAME.
- A MODERATE HEAT RISK WILL PERSIST THROUGH TUESDAY,
PARTICULARLY IMPACTING INDIVIDUALS SENSITIVE TO HIGH
TEMPERATURES OR THOSE LACKING SUFFICIENT COOLING AND
HYDRATION.
DISCUSSION
ISSUED AT 243 AM CDT SAT MAY 16 2026
A COMPLEX MESOSCALE ENVIRONMENT IS UNFOLDING ACROSS THE MIDWEST
THIS MORNING. REGIONAL RADAR MOSAICS HIGHLIGHT A PAIR OF
OUTFLOW BOUNDARIES CURRENTLY SAGGING INTO CENTRAL ILLINOIS,
DOWNSTREAM OF DECAYING CONVECTION OVER IOWA. TO THE WEST, A PAIR
OF SHORTWAVE TROUGHS POSITIONED OVER NORTH-CENTRAL MISSOURI AND
SOUTHEAST NEBRASKA ARE PROGGED TO TRAVERSE THE LOCAL AREA LATER
THIS MORNING INTO THE EARLY AFTERNOON. SUPPORTED BY A MODEST
LOW-LEVEL JET (LLJ), THESE FEATURES WILL ENCOUNTER A
SUFFICIENTLY BUOYANT AIRMASS CHARACTERIZED BY MUCAPE VALUES IN
THE 2500-3000 J/KG RANGE.
EXPECT CONVECTION TO BLOSSOM ACROSS PORTIONS OF CENTRAL
ILLINOIS LATER THIS MORNING AND THROUGHOUT THE AFTERNOON. WHILE
THE RIPPLES IN THE FLOW MAY PROVIDE SOME LOCAL ENHANCEMENT TO
DEEP-LAYER SHEAR, VALUES ARE GENERALLY EXPECTED TO REMAIN AROUND
30 KTS OR LESS. THIS SHOULD LIMIT THE POTENTIAL FOR WIDESPREAD
ORGANIZED SEVERE WEATHER; HOWEVER, A MARGINAL RISK (LEVEL 1 OF
5) REMAINS IN PLACE. THE PRIMARY THREATS WITH THE MORE ROBUST
CORES WILL BE ISOLATED DAMAGING WIND GUSTS UP TO 60 MPH AND
LARGE HAIL UP TO THE SIZE OF GOLF BALLS.
OF ADDITIONAL CONCERN IS THE POTENTIAL FOR LOCALIZED HYDRO
ISSUES. WITH SLOW-MOVING CONVECTIVE OUTFLOWS AND A HIGH-MOISTURE
ENVIRONMENT, TRAINING OR BACKBUILDING CELLS COULD PRODUCE HEAVY
RAINFALL. THE 00Z HREF LPMM QPF INDICATES A SIGNAL FOR 3-4 INCH
TOTALS, PARTICULARLY OVER EAST-CENTRAL OR SOUTHEAST ILLINOIS, A
TREND SUPPORTED BY RECENT HRRR RUNS.
CENTRAL ILLINOIS WILL REMAIN FIRMLY ENTRENCHED IN THE WARM
SECTOR THROUGH THE REMAINDER OF THE WEEKEND. HUMID CONDITIONS
WILL PERSIST WITH TEMPERATURES CLIMBING INTO THE MID-80S. WHILE
ZONAL MID-LEVEL FLOW AND SUBTLE SHORTWAVES MAY TRIGGER ISOLATED
TO WIDELY SCATTERED SHOWERS AND STORMS, THE LACK OF ROBUST DEEP-
LAYER SHEAR (GENERALLY LESS THAN 30 KTS) WILL KEEP THE SEVERE
THREAT DISORGANIZED AND LOW-IMPACT.
THE SYNOPTIC FOCUS SHIFTS SIGNIFICANTLY TOWARD THE MONDAY-
TUESDAY TIMEFRAME AS A POTENT UPPER-LEVEL WAVE PIVOTS OUT OF THE
GREAT BASIN AND LIFTS INTO THE NORTHERN PLAINS. AN ASSOCIATED
COLD FRONT WILL SWEEP INTO THE MID-MISSISSIPPI VALLEY,
ENCOUNTERING A HIGHLY UNSTABLE ENVIRONMENT WITH MLCAPES
EXCEEDING 2500 J/KG. UNLIKE THE WEEKEND ACTIVITY, THIS SYSTEM
WILL BE ACCOMPANIED BY A NOTABLE INCREASE IN KINEMATIC SUPPORT,
WITH DEEP-LAYER SHEAR INCREASING INTO THE 30-40 KT RANGE. THIS
ENVIRONMENT IS CONDUCIVE TO ORGANIZED, HIGH-IMPACT SEVERE
WEATHER, AND THIS PERIOD WILL NEED TO BE MONITORED CLOSELY FOR
POTENTIAL UPGRADES IN RISK CATEGORIES.
MODEL CONSISTENCY BEGINS TO DIVERGE SLIGHTLY BY MID-WEEK
REGARDING THE TIMING OF THE FRONTAL PASSAGE. SHOULD THE FRONT
SLOW, LINGERING MOISTURE AND INSTABILITY COULD SUPPORT RE-
DEVELOPMENT ON WEDNESDAY, LIKELY CONFINED TO AREAS ALONG AND
SOUTH OF THE I-70 CORRIDOR. BY THURSDAY AND FRIDAY, A TRANSITION
TO A COOLER AND MORE STABLE POST-FRONTAL REGIME IS ANTICIPATED
AS HIGH PRESSURE BEGINS TO BUILD INTO THE REGION. MID-RANGE
DETERMINISTIC GUIDANCE DOES SHOW SEMBLANCE OF ANOTHER FRONTAL
PASSAGE IN THE FRIDAY-SATURDAY TIMEFRAME, BUT MOISTURE RETURN
AHEAD OF THE FRONT LOOKS TOO POOR TO SUPPORT APPRECIABLE RAIN
CHANCES THEN, AT LEAST FOR NOW.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 556 AM CDT SAT MAY 16 2026
SCATTERED SHOWERS AND THUNDERSTORMS WILL PUSH ACROSS THE
REGIONAL TERMINALS THROUGH 18Z, WITH THE GREATEST COVERAGE AT
KCMI AND KDEC. ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY MAY
REDEVELOP AFTER 18Z. THE PROBABILITY IS GREATER THAN 30% BUT
LESS THAN 50%, AND SO A PROB30 GROUP FOR SHRA/TRSA HAS BEEN
ADDED TO ALL REGIONAL TERMINALS BETWEEN 18Z-00Z. BY LATE
TONIGHT, ANOTHER ROUND OF SHOWERS COULD PUSH INTO WEST- CENTRAL
ILLINOIS FROM SOUTHEAST IOWA, PRIMARILY AFTER 03Z, AND THIS
WOULD AFFECT MAINLY THE KPIA TERMINAL.
WHILE THE DOMINANT FLIGHT CATEGORY IS EXPECTED TO REMAIN VFR
THROUGH THIS TAF PERIOD, THERE IS POTENTIAL FOR MVFR CEILINGS
WHEREVER THUNDERSTORMS OCCUR.
OTHERWISE, WINDS WILL MOSTLY BE FROM THE SOUTH THIS AFTERNOON
WITH SUSTAINED SPEEDS BETWEEN 10-15 KTS AND OCCASIONAL GUSTS UP
TO 20-25 KTS BEFORE DIMINISHING THIS EVENING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...MJA
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