642
FXUS63 KILX 301702
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1202 PM CDT TUE JUN 30 2026
KEY MESSAGES
- HOT AND HUMID WEATHER WILL PREVAIL FOR THE NEXT SEVERAL
DAYS...WITH PEAK AFTERNOON HEAT INDEX READINGS EXCEEDING 105
DEGREES THROUGH AT LEAST THURSDAY.
- RAIN CHANCES WILL GRADUALLY RETURN BY THE END OF THE WEEK INTO
THE HOLIDAY WEEKEND. THE LATEST NBM INDICATES A 30-50% CHANCE
FOR THUNDERSTORMS ON JULY 4TH.
DISCUSSION
ISSUED AT 235 AM CDT TUE JUN 30 2026
**** HOT AND HUMID WEATHER CONTINUES ****
07Z/2AM UPPER AIR ANALYSIS SHOWS A PROMINENT 596DM HIGH CENTERED
OVER THE OHIO RIVER VALLEY WHILE A 558DM LOW SPINS ACROSS
SOUTHERN SASKATCHEWAN. AS THE HIGH REMAINS ESSENTIALLY IN PLACE
AND THE LOW LIFTS NORTHEASTWARD, THE PRIMARY CONVECTIVE ZONE
WILL FOCUS FROM NEBRASKA TO MICHIGAN THROUGH THURSDAY. MEANWHILE
FURTHER SOUTH, CENTRAL ILLINOIS WILL REMAIN HIGH AND DRY WITH
TYPICAL SUMMERTIME HEAT AND HUMIDITY. THE NBM CONTINUES TO BE
ABOUT 2-4 DEGREES TOO WARM WITH ITS HIGH TEMPERATURES FORECAST,
SUGGESTING READINGS POTENTIALLY CLIMBING INTO THE UPPER 90S IN A
FEW SPOTS BOTH TODAY AND WEDNESDAY. WHILE THERE WILL BE
CONSIDERABLY LESS HIGH CLOUD COVER AROUND AND UPPER HEIGHTS WILL
REMAIN HIGH, COPIOUS BOUNDARY LAYER MOISTURE WILL MITIGATE
TEMPS. AS A RESULT, AM EXPECTING HIGHS MOSTLY IN THE LOWER 90S
TODAY...THEN THE MIDDLE 90S FOR BOTH WEDNESDAY AND THURSDAY. THE
HEAT COUPLED WITH DEWPOINTS WELL INTO THE 70S WILL LEAD TO HEAT
INDEX READINGS PEAKING AT OR ABOVE 105 DEGREES THROUGH AT LEAST
THURSDAY. THE HEAT WILL EASE A BIT BY THE END OF THE WEEK DUE
TO DECREASING UPPER HEIGHTS AND INCREASING CLOUD COVER/POPS.
**** THUNDERSTORMS FOR THE HOLIDAY WEEKEND ****
A SERIES OF SHORT-WAVE TROUGHS EJECTING FROM THE SOUTHERN
ROCKIES INTO THE GREAT LAKES WILL FLATTEN THE PREVAILING UPPER
RIDGE AXIS CURRENTLY OVER THE MIDWEST, RESULTING IN THE RETURN
OF FLAT WEST-TO-EAST ZONAL FLOW BY THE END OF THE WEEK. ONCE
THIS HAPPENS, ADDITIONAL WAVES TRAVERSING THE PLAINS WILL LEAD
TO INCREASING RAIN CHANCES DURING THE FRIDAY THROUGH SUNDAY
TIMEFRAME. THE 00Z JUN 30 MODEL SUITE CONTINUES TO SUGGEST THE
FIRST WAVE TRACKING THROUGH THE REGION ON FRIDAY, ALBEIT
SLIGHTLY FURTHER NORTH THAN PREVIOUSLY THOUGHT. WITH THE MAIN
BAROCLINIC ZONE STILL DRAPED TO THE NORTH, THINK THE PRIMARY
FOCUS FOR SHOWERS/THUNDER ON FRIDAY WILL BE ALONG/NORTH OF I-80.
THE SHOWERS WILL BE MUCH LESS NUMEROUS FURTHER SOUTH INTO
CENTRAL ILLINOIS, BUT HAVE INCLUDED 40-60 POPS AS FAR SOUTH AS
THE I-74 CORRIDOR. ONCE THE INITIAL WAVE PASSES, IT WILL NUDGE
THE FRONTAL BOUNDARY INTO NORTH-CENTRAL ILLINOIS ON SATURDAY,
SETTING THE STAGE FOR SCATTERED SHOWERS/THUNDER FOR JULY 4TH.
THE LATEST NBM SHOWS A 30-50% CHANCE FOR THUNDERSTORMS DURING
THE AFTERNOON AND EVENING. STAY TUNED TO LATER FORECASTS FOR
MORE DETAILS. AFTER THAT, ANOTHER WAVE AND ITS ASSOCIATED COLD
FRONT WILL PASS THROUGH THE REGION ON SUNDAY...BRINGING MORE
SHOWERS. AS NOTED BY THE PAST FEW MODEL CYCLES, ALL SYNOPTIC
MODELS FEATURE THE OHIO RIVER VALLEY UPPER RIDGE FLATTENING BY
THE END OF THE WEEK...THEN SHIFTING/RE-DEVELOPING FURTHER WEST
ACROSS THE DESERT SOUTHWEST BY EARLY NEXT WEEK. AS RIDGING
BUILDS IN THE ROCKIES, WEAK TROUGHING WILL FORM DOWNSTREAM OVER
THE MIDWEST...PUSHING THE COLD FRONT THROUGH CENTRAL ILLINOIS
SUNDAY NIGHT INTO MONDAY MORNING. THE END RESULT WILL BE
DECREASING PRECIP CHANCES/TEMPS BY MONDAY AS HIGHS DROP BACK
INTO THE MIDDLE TO UPPER 80S.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1144 AM CDT TUE JUN 30 2026
VFR CONDITIONS WILL PERSIST THROUGH THIS TAF CYCLE AS AN
EXPANSIVE HEAT RIDGE SUPPRESSES CLOUD COVER AND PRECIPITATION
CHANCES. THE ONLY FAILURE MODE COULD BE PATCHY SHALLOW FOG
AROUND THE 12Z PERIOD, WHICH MAY BRIEFLY LOWER VISIBILITY INTO
THE MVFR RANGE.
SURFACE WINDS WILL REMAIN FROM THE SOUTH AROUND 10 KTS.
ILX WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WARNING UNTIL MIDNIGHT CDT THURSDAY NIGHT FOR
ILZ027>031-036>038-040>057-061>063-066>068-071>073.
KEY MESSAGES...BARNES
DISCUSSION...BARNES
AVIATION...MJA
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