295
FXUS63 KILX 182248
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
548 PM CDT FRI SEP 18 2026
KEY MESSAGES
- UNSEASONABLE HEAT & TEMPERATURE CONTRAST: AREAS SOUTH OF THE
FRONT WILL SEE HEAT INDICES NEAR 100 F THROUGH SATURDAY. THIS
IS PRIMARILY NEAR AND SOUTH OF INTERSTATE 72.
- THUNDERSTORMS & MICROBURST RISK: SCATTERED SHOWERS AND STORMS
ARE FORECAST THROUGH SUNDAY. ON SATURDAY, STRONGER STORMS
COULD PRODUCE LOCALIZED DAMAGING WIND GUSTS UP TO 60 MPH AND
QUARTER-SIZED HAIL.
- SIGNIFICANTLY COOLER NEXT WEEK: HIGH CONFIDENCE THAT THE HOT
AIR WILL BE PUSHED SOUTH BY MONDAY. EXPECT COMFORTABLE, DRY
CONDITIONS WITH HIGHS IN THE UPPER 60S TO MID-70S AREAWIDE
TUESDAY THROUGH FRIDAY.
DISCUSSION
ISSUED AT 1231 PM CDT FRI SEP 18 2026
AN ANOMALOUS 594-MB HEAT RIDGE CONTINUES TO HOLD FIRM OVER THE
CENTRAL U.S. EARLY THIS AFTERNOON. POSITIONED ALONG THE NORTHERN
PERIPHERY OF THIS HEAT DOME, A WEAK SURFACE LOW RESTS NEAR
SIOUX CITY, IOWA, WITH AN ASSOCIATED WARM FRONT STRETCHING
SOUTHEASTWARD THROUGH COLUMBIA, MISSOURI TOWARD TERRE HAUTE,
INDIANA.
AS WEAK SHORTWAVE ENERGY EJECTS OUT OF THE DESERT SOUTHWEST, IT
WILL RIDE OVER THE FRONTAL BOUNDARY, OFFERING SUFFICIENT
SYNOPTIC LIFT TO DRIVE SCATTERED SHOWER ACTIVITY TODAY. THESE
SHORTWAVES WILL ALSO PUSH THE FRONTAL SYSTEM SLIGHTLY NORTH
FROM TONIGHT INTO SATURDAY.
NEAR THE WARM FRONT, POOLING SURFACE DEWPOINTS IN THE LOWER 70S
WILL HELP SUPPORT MLCAPE AROUND 2000 J/KG, KEEPING THE
POTENTIAL FOR AN ISOLATED THUNDERSTORM IN PLACE. POOR MID-LEVEL
LAPSE RATES WILL LIMIT ANY SEVERE THREAT TODAY. HOWEVER, AS THE
FRONT DRIFTS NORTHWARD ON SATURDAY, INCREASING BULK SHEAR (2535
KTS) MAY COMPENSATE FOR THE WEAK LAPSE RATES, ALLOWING FOR
OCCASIONALLY ORGANIZED STORMS CAPABLE OF PRODUCING LOCALIZED
SEVERE MICROBURST WINDS AND QUARTER-SIZED HAIL. BRIEF HEAVY
DOWNPOURS RESULTING IN 1"/HR RATES ARE A LOW (10-20%)
PROBABILITY, BUT COULD ACCOMPANY THE MORE ORGANIZED CONVECTION.
THIS POTENTIAL IS BEST HIGHLIGHTED BY THE HREF LPMM QPF, WHICH
HINTS AT LOCALIZED AMOUNTS UP TO 1.5".
BEYOND THE SCATTERED SHOWERS AND ISOLATED STORM POTENTIAL
THROUGH SATURDAY, THE PRIMARY FORECAST DIFFICULTY CENTERS ON THE
SHARP TEMPERATURE CONTRAST ACROSS THE REGION. WITH THE BOUNDARY
DRAPED ACROSS CENTRAL ILLINOIS, LOCATIONS TO THE NORTH WILL BE
CAPPED IN THE 80S, WHEREAS AREAS TO THE SOUTH WILL CLIMB BACK
INTO THE 90S WITH HEAT INDICES APPROACHING 100 F. OUTFLOW FROM
PASSING PRECIPITATION COULD LEAD TO SHARP LOCAL VARIATIONS IN
TEMPERATURES THROUGH SATURDAY.
BY SUNDAY, MODEL GUIDANCE AND ENSEMBLE SUITES EXHIBIT HIGH
CONFIDENCE THAT A CLOSED UPPER-LEVEL TROUGH WILL TRACK EAST
ACROSS THE PLAINS AND INTO THE MID-MISSISSIPPI VALLEY BY MONDAY.
THIS SYSTEM WILL DISMANTLE THE HEAT RIDGE AND PUSH THE FRONTAL
BOUNDARY SOUTH AND EAST OF THE FORECAST AREA. IN ITS WAKE,
EXPANSIVE HIGH PRESSURE WILL SETTLE IN UNDER A BLOCKING SPLIT-
FLOW REGIME ALOFT, BRINGING A PERIOD OF DRIER AND SIGNIFICANTLY
COOLER CONDITIONS. DAYTIME HIGHS FROM TUESDAY THROUGH FRIDAY ARE
EXPECTED TO REMAIN IN THE UPPER 60S TO MID 70S.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 548 PM CDT FRI SEP 18 2026
KBMI-KCMI ARE NEAR THE SOUTHERN EDGE OF THE IFR CLOUD DECK, AND
THESE LOW CEILINGS SHOULD SCATTER OUT SOON. MVFR CEILINGS ARE
FORECAST TO SHIFT BACK SOUTH LATER TONIGHT, AFFECTING KPIA-
KBMI-KCMI WELL INTO SATURDAY MORNING. A DISTURBANCE WILL BRING A
CHANCE OF SCATTERED TSRA AROUND MIDDAY, AND THIS IS ACCOUNTED
FOR WITH PROB30 GROUPS FOR LOW DUE TO LOW CONFIDENCE. EAST WINDS
WILL GRADUALLY VEER SOUTHEAST OVERNIGHT AND ON SATURDAY, NEAR TO
UNDER 10 KT.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...25
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