653
FXUS63 KILX 170911
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
411 AM CDT SUN MAY 17 2026
KEY MESSAGES
- WARM TEMPERATURES WILL CREATE A MODERATE HEAT RISK THIS
AFTERNOON. ADDITIONALLY, STRONG SOUTH WINDS GUSTING UP TO 35
MPH COULD GENERATE LOCALIZED BLOWING DUST, ABRUPTLY REDUCING
VISIBILITY TO UNDER ONE MILE NEAR ACTIVE FARM FIELDS.
- MULTIPLE ROUNDS OF SEVERE THUNDERSTORMS WILL MOVE INTO THE
REGION MONDAY, BRINGING A PRIMARY THREAT OF DAMAGING WINDS AND
LARGE HAIL. THIS HAZARDOUS WEATHER IMPACTS WEST-CENTRAL
ILLINOIS STARTING MONDAY MORNING BUT COULD EXTEND THROUGH THE
NIGHT.
- SEVERE STORMS REMAIN A THREAT TUESDAY AFTERNOON AND EVENING,
TARGETING AREAS NEAR AND SOUTH OF INTERSTATE 72. HEAVY MORNING
CLOUD COVER INTRODUCES HIGH UNCERTAINTY, WHICH MAY DICTATE THE
ULTIMATE STRENGTH AND POSITION OF THE TUESDAY
AFTERNOON/EVENING STORMS.
DISCUSSION
ISSUED AT 338 AM CDT SUN MAY 17 2026
EARLY MORNING SATELLITE AND RADAR TRENDS DEPICT AN AREA OF
FESTERING CONVECTION IN THE VICINITY OF A SURFACE FRONT
EXTENDING FROM EASTERN NEBRASKA TO WESTERN ILLINOIS. CONVECTIVE-
ALLOWING MODELS (CAMS) REMAIN IN EXCELLENT AGREEMENT THAT THIS
ACTIVITY WILL HOLD NORTH AND WEST OF THE LOCAL FORECAST AREA,
FOLLOWING THE PRIMARY UPPER-LEVEL FORCING AS A SHORTWAVE LIFTS
ACROSS EASTERN IOWA AND INTO WISCONSIN LATER THIS MORNING. AS IT
DOES SO, THE FEATURE WILL DRAG THE EFFECTIVE SURFACE BOUNDARY
NORTHWARD INTO NORTHERN ILLINOIS BY MIDDAY.
WITH CENTRAL ILLINOIS FIRMLY ENTRENCHED IN THE WARM SECTOR,
TEMPERATURES ARE FORECAST TO SURGE WELL INTO THE 80S THIS
AFTERNOON AS SKIES GRADUALLY CLEAR FOLLOWING THE DEPARTURE OF
EARLY MORNING CONVECTIVE DEBRIS. THE COMBINATION OF INTENSE
SOLAR HEATING AND MID-60S DEWPOINTS WILL YIELD A MODERATE HEAT
RISK, PARTICULARLY IMPACTING INDIVIDUALS SENSITIVE TO HIGH
TEMPERATURES OR THOSE LACKING SUFFICIENT COOLING AND HYDRATION.
ASIDE FROM THE HEAT RISK, A TIGHTENING PRESSURE GRADIENT AND
DEEP BOUNDARY LAYER MIXING WILL SUPPORT SOUTH WIND GUSTS OF 25
TO 35 MPH THIS AFTERNOON. GIVEN ONGOING AGRICULTURAL ACTIVITY
ACROSS THE REGION, ISOLATED CHANNELS OF BLOWING DUST COULD BE A
DISTINCT HAZARD. THIS ENVIRONMENT COULD LOCALLY AND ABRUPTLY
REDUCE VISIBILITIES TO ONE MILE OR LESS IN AND NEAR ACTIVE FIELD
WORK.
THE SYNOPTIC PATTERN EVOLVES RAPIDLY BY MONDAY AS A VIGOROUS
UPPER-LEVEL DISTURBANCE EMERGES FROM THE GREAT BASIN TOWARD THE
NORTHERN PLAINS. AHEAD OF THIS MAIN TROUGH, SEVERAL SHORTWAVES
WILL TRACK INTO THE CORN BELT, POTENTIALLY TRIGGERING MULTIPLE
ROUNDS OF PREFRONTAL STORMS THROUGHOUT THE DAY. THIS ACTIVITY
WILL BE FUELED BY AN INFLUX OF NEAR-70 DEGREE SURFACE DEWPOINTS
ALONG A VEERING LOW-LEVEL JET (LLJ), COMBINED WITH STEEP MID-
LEVEL LAPSE RATES WITHIN AN ADVECTING ELEVATED MIXED LAYER
(EML). THESE FACTORS SHOULD SUSTAIN CONVECTIVE CLUSTERS AS THEY
MOVE INTO WEST-CENTRAL ILLINOIS DURING THE MORNING HOURS AMID AN
INCREASE IN DEEP-LAYER SHEAR (30-40 KTS).
CURRENT PROJECTIONS FAVOR A LINEAR STORM MODE FOR MONDAY DUE TO
THE POOR CROSSOVER FLOW ANGLES BETWEEN THE 500-850 MB LEVELS.
CONSEQUENTLY, DAMAGING WINDS ARE EXPECTED TO BE THE PRIMARY
THREAT, ALTHOUGH LARGE HAIL REMAINS A POSSIBILITY WITHIN THE
MORE VIGOROUS UPDRAFTS.
THE SEVERE THREAT CONTINUES INTO LATE MONDAY NIGHT AND TUESDAY
MORNING AS ADDITIONAL SHORTWAVES INTERACT WITH A 40-50 KT LLJ
CORE POSITIONED OVER THE FORECAST AREA, LIKELY SUSTAINING
FURTHER CONVECTIVE DEVELOPMENT AHEAD OF THE APPROACHING COLD
FRONT.
TUESDAY'S OUTLOOK REMAINS HIGHLY UNCERTAIN DUE TO THE POTENTIAL
IMPACT OF MORNING CONVECTION. IF CLOUD COVER AND PRECIPITATION
PERSIST, AFTERNOON DESTABILIZATION COULD BE LIMITED, MAKING THE
SEVERE THREAT MORE CONDITIONAL THAN ON MONDAY. THE HIGHEST RISK
CURRENTLY APPEARS FOCUSED SOUTH OF INTERSTATE 72 AND ACROSS
SOUTHEAST ILLINOIS, WHERE THE ENVIRONMENT IS MOST LIKELY TO
RECOVER AHEAD OF THE FRONT. WHILE INITIAL DEVELOPMENT IN THIS
REGION COULD BE DISCRETE AND SUPERCELLULAR GIVEN THE INSTABILITY
AND SHEAR, THE NEAR-PARALLEL ORIENTATION OF SHEAR VECTORS TO
THE FRONT SUGGESTS A RAPID TRANSITION INTO A LINEAR MCS AS THE
BOUNDARY MOVES THROUGH TUESDAY EVENING.
MID-WEEK GUIDANCE SHOWS SOME MINOR DISCREPANCIES REGARDING THE
COLD FRONTS EXIT SPEED. A SLOWER PROGRESSION COULD ALLOW FOR
LINGERING MOISTURE TO SPARK ADDITIONAL STORMS ON WEDNESDAY,
PRIMARILY ALONG AND SOUTH OF THE I-70 CORRIDOR. HOWEVER, A MORE
STABLE, COOLER POST-FRONTAL REGIME IS EXPECTED TO TAKE HOLD BY
THURSDAY AND FRIDAY AS CONTINENTAL HIGH PRESSURE MOVES INTO THE
MIDWEST. WHILE DETERMINISTIC MODELS HINT AT ANOTHER BOUNDARY
PASSING THROUGH LATE IN THE WEEK, MOISTURE RETURN APPEARS
INSUFFICIENT TO SUPPORT SIGNIFICANT PRECIPITATION CHANCES AT
THIS TIME.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1229 AM CDT SUN MAY 17 2026
A WARM FRONT LIFTING ACROSS THE AREA WILL BRING INCREASING WINDS
AND A SHIFT FROM SSE TO S DIRECTION. OTHERWISE, VFR CONDITIONS
ARE LIKELY OVER MOST OF THE AREA, ALTHOUGH THERE REMAINS A LOW
PROBABILITY FOR -TSRA AT KPIA PRIOR TO 10Z. WINDS S-SE 8-12 KTS,
BECOMING S 18-20 KTS WITH GUSTS AROUND 30 KTS AFTER 16Z.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...37
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