541
FXUS63 KILX 171743
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1243 PM CDT SUN MAY 17 2026
KEY MESSAGES
- SOUTHERLY WINDS GUSTING 25-35MPH MAY CREATE PATCHY BLOWING
DUST WHERE ACTIVE FIELDWORK IS ONGOING...PARTICULARLY ALONG
AND NORTH OF A MASON CITY TO CHAMPAIGN LINE WHERE THE LIGHTEST
RAINFALL OCCURRED YESTERDAY.
- THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER
ACROSS ALL OF CENTRAL AND SOUTHEAST ILLINOIS ON MONDAY AND
AGAIN ON TUESDAY.
UPDATE
ISSUED AT 1002 AM CDT SUN MAY 17 2026
UPDATED THE FORECAST THIS MORNING TO INCREASE CLOUD COVER AND
DROP THE AFTERNOON HIGHS BY A COUPLE OF DEGREES. 1430Z/930AM
SATELLITE IMAGERY SHOWS A THICK BLANKET OF MID/HIGH CLOUDS
ACROSS MUCH OF CENTRAL ILLINOIS, WHICH HAS BEEN ACTING TO SLOW
THE DIURNAL RISE OF TEMPS DESPITE STRONG SOUTHERLY WINDS. BASED
ON SATELLITE TRENDS AND RH PROFILES, THINK SKIES WILL REMAIN
MOSTLY CLOUDY FOR MUCH OF THE DAY...FOLLOWED BY INCREASING
AMOUNTS OF SUNSHINE BY MID TO LATE AFTERNOON. AM STILL EXPECTING
VERY WARM TEMPS, BUT HAVE LOWERED HIGHS MOSTLY INTO THE MIDDLE
80S. SOUTHERLY WINDS ARE ALREADY GUSTING 25-30MPH AND WILL
CONTINUE TO DO SO THROUGH THE REMAINDER OF THE DAY. GIVEN THE
GUSTY WINDS, THERE IS A MINOR CONCERN FOR PATCHY BLOWING DUST
ALONG/NORTH OF A MASON CITY TO CHAMPAIGN LINE WHERE VERY LITTLE
RAIN FELL YESTERDAY. WILL KEEP AN EYE ON OBSERVATIONS AND ISSUE
AN ADVISORY AS NECESSARY. FOR NOW, THINK MENTION OF PATCHY
BLOWING DUST IN THE FORECAST IS SUFFICIENT.
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 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. THE HIGHEST RISK MAY ULTIMATELY
FOCUS 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 /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1243 PM CDT SUN MAY 17 2026
SOUTHERLY WINDS WILL GUST 25-30KT AT THE CENTRAL ILLINOIS
TERMINALS THIS AFTERNOON BEFORE GUSTS DECREASE SLIGHTLY INTO THE
20-25KT RANGE AFTER SUNSET. MODELS CONTINUE TO SHOW A STRONG
NOCTURNAL JET DEVELOPING TONIGHT, SO HAVE INCLUDED 50KT OF
LOW-LEVEL WIND SHEAR AT ALL SITES ACCORDINGLY. ASIDE FROM THE
WIND, THE OTHER MAIN AVIATION FORECASTING CHALLENGE WILL BE THE
POTENTIAL FOR CONVECTION LATE TONIGHT INTO MONDAY MORNING. ALL
MODELS SHOW STORMS FIRING ACROSS WESTERN IOWA INTO KANSAS THIS
EVENING...BUT THE EASTWARD EVOLUTION/TIMING OF THE CONVECTION
REMAINS SOMEWHAT IN QUESTION. BASED ON OVERALL CONSENSUS, IT
APPEARS LIKELY THAT A BROKEN LINE OF STORMS WILL PUSH INTO THE
ILLINOIS RIVER VALLEY AROUND DAWN, THEN DROP SOUTHEASTWARD TO
THE I-72 CORRIDOR TOWARD MIDDAY. GIVEN INCREASING CONFIDENCE FOR
CONVECTION, HAVE INCLUDED A TEMPO GROUP FOR THUNDER AT KPIA
BETWEEN 12Z AND 16Z AND AT THE I-72 TERMINALS BETWEEN 14Z AND
18Z. WITH MUCH RICHER BOUNDARY LAYER MOISTURE IN PLACE, THINK
CEILINGS WILL LOWER TO MVFR WITHIN THE CONVECTION.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...BARNES
UPDATE...BARNES
DISCUSSION...MJA
AVIATION...BARNES
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