478
FXUS63 KILX 011751
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1251 PM CDT WED JUL 1 2026
KEY MESSAGES
- HOT AND HUMID WEATHER WILL PREVAIL FOR THE NEXT SEVERAL DAYS,
WITH PEAK AFTERNOON HEAT INDEX READINGS PEAKING 100 TO 110
DEGREES THROUGH AT LEAST FRIDAY.
- RAIN CHANCES WILL GRADUALLY RETURN BY THE END OF THE WEEK INTO
THE 4TH OF JULY HOLIDAY WEEKEND. THE LATEST NBM INDICATES A
40-70% CHANCE FOR THUNDERSTORMS ON JULY 4TH.
DISCUSSION
ISSUED AT 343 AM CDT WED JUL 1 2026
**** HOT AND HUMID WEATHER CONTINUES ****
07Z/2AM UPPER AIR ANALYSIS SHOWS A PROMINENT 595DM HIGH
CENTERED OVER THE OHIO RIVER VALLEY WHILE A 555DM LOW SPINS
ACROSS MANITOBA. 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 TEMPERATURE FORECAST,
SUGGESTING READINGS IN THE MIDDLE TO UPPER 90S IN A FEW SPOTS
BOTH TODAY AND THURSDAY. BASED ON CONSISTENCY AND A CONTINUED
VERY MOIST BOUNDARY LAYER THAT WILL TEMPER HEATING, HAVE
UNDERCUT THE NBM AND GONE WITH HIGHS IN THE LOWER TO MIDDLE 90S
BOTH DAYS. NAM/RAP FORECAST SOUNDINGS SHOW MIXING UP TO ABOUT
5000FT THIS AFTERNOON, WHICH IS 1000FT DEEPER THAN YESTERDAY.
THIS HAS THE POTENTIAL TO BRING SLIGHTLY LOWER DEWPOINTS DOWN TO
THE SURFACE LATER IN THE DAY AS EVIDENCED BY THE RAP/HRRR
SHOWING READINGS MIXING INTO THE UPPER 60S. THINK THIS MAY BE A
BIT TOO EXTREME, ESPECIALLY CONSIDERING THE VERY MOIST GROUND
CONDITIONS AND ACTIVELY GROWING CROPS. HAVE THEREFORE USED AN
NBM/CONSALL BLEND TO NUDGE DEWPOINTS DOWN INTO THE LOWER TO
MIDDLE 70S THIS AFTERNOON AS OPPOSED TO THE UPPER 70S TO NEAR 80
DEGREE READINGS FROM YESTERDAY. DESPITE THE LOWER DEWPOINTS,
CORRESPONDING PEAK HEAT INDEX READINGS WILL STILL TOP OUT AROUND
105 DEGREES.
**** THUNDERSTORMS FOR THE HOLIDAY WEEKEND ****
A SERIES OF SHORT-WAVES EJECTING NORTHEASTWARD FROM THE SOUTHERN
ROCKIES TO THE GREAT LAKES WILL FLATTEN THE PREVAILING UPPER
RIDGE...RESULTING IN A WEST-TO-EAST ZONAL FLOW PATTERN ACROSS
THE MIDWEST FRIDAY THROUGH SUNDAY. THE FIRST WAVE WILL INTERACT
WITH A NOCTURNAL LOW-LEVEL JET STREAK TO TRIGGER AN MCS ACROSS
SOUTH DAKOTA/NEBRASKA THURSDAY EVENING...WITH THE STORM CLUSTER
THEN PUSHING MAINLY EASTWARD INTO WISCONSIN/NORTHERN ILLINOIS
BY FRIDAY MORNING. THERE IS STILL SOME UNCERTAINTY REGARDING THE
EXACT TRACK OF THE CONVECTION, BUT THE SYNOPTIC PATTERN STRONGLY
SUGGESTS IT WILL REMAIN NORTH OF THE KILX CWA. HAVE INCLUDED
30-50 POPS AS FAR SOUTH AS THE I-72 CORRIDOR LATE THURSDAY NIGHT
INTO FRIDAY MORNING, BUT THINK THE BULK OF THE PRECIP WILL STAY
NORTH. THE BIG QUESTION FOR CENTRAL ILLINOIS WILL BE WHERE THE
RESIDUAL OUTFLOW BOUNDARY LAYS OUT, AS THIS WILL BE THE FOCUS
FOR CONVECTIVE RE-DEVELOPMENT FRIDAY AFTERNOON AND EVENING. THE
00Z RRFS SHOWS THE BOUNDARY FIRING ALONG/NORTH OF I-72, AND THIS
SEEMS REASONABLE BASED ON THE EXPECTED MORNING STORM TRAJECTORY.
ANY AFTERNOON STORMS THAT DEVELOP WILL HAVE ACCESS TO RICH
BOUNDARY LAYER MOISTURE WITH SURFACE DEWPOINTS IN THE MIDDLE TO
UPPER 70S AND CORRESPONDING STRONG INSTABILITY WITH SBCAPES IN
EXCESS OF 3000J/KG. THE MISSING FACTOR FOR ORGANIZED SEVERE
WEATHER WILL BE WIND SHEAR, AS THE NAM/GFS SHOW 0-6KM BULK
SHEAR OF JUST 20-25KT. THE LATEST DAY 3 SPC CONVECTIVE OUTLOOK
HIGHLIGHTS ALL OF CENTRAL ILLINOIS WITH A MARGINAL RISK (LEVEL 1
OF 5) FOR SEVERE WEATHER ON FRIDAY. GIVEN THE LACK OF SHEAR AND
A STRONG FORCING MECHANISM, THE LOW RISK IS APPROPRIATE. THINK
THE SCATTERED CELLS THAT FORM FRIDAY AFTERNOON AND EVENING WILL
BE CAPABLE OF SPORADIC STRONG WIND GUSTS AS WELL AS LOCALLY
TORRENTIAL DOWNPOURS.
A SECOND SHORT-WAVE WILL TRIGGER ANOTHER MCS ACROSS THE SAME
AREA (SOUTH DAKOTA/NEBRASKA) FRIDAY EVENING: HOWEVER, THIS
SYSTEM MAY TAKE A MORE E/SE TRACK ACROSS NORTH-CENTRAL ILLINOIS
LATE FRIDAY NIGHT INTO SATURDAY. AS A RESULT, THE NBM HAS
INCREASED POPS INTO THE 40-70% RANGE FOR JULY 4TH. WHILE WIND
SHEAR WILL REMAIN MEAGER AND THE OVERALL SEVERE WEATHER RISK
WILL LIKELY STAY LOW, AM CONCERNED THAT THE STORMS WILL BE
EFFICIENT RAIN-PRODUCERS AND WILL PRODUCE POCKETS OF VERY HEAVY
RAINFALL. WPC NOW SHOWS A MARGINAL RISK (5-15% CHANCE) FOR
EXCESSIVE RAINFALL FOR BOTH FRIDAY AND SATURDAY ACCORDINGLY.
WHILE THE HOLIDAY WEEKEND WILL NOT BE A COMPLETE WASH-OUT,
CENTRAL ILLINOIS RESIDENTS SHOULD KEEP A CLOSE EYE ON THE
FORECAST AND BE AWARE THAT SOME OUTDOOR ACTIVITIES MAY BE
IMPACTED. AFTER THAT, THE UPPER RIDGE WILL RE-DEVELOP FURTHER
WEST ACROSS THE DESERT SOUTHWEST. THIS WILL LEAD TO WEAK
DOWNSTREAM TROUGHING OVER THE MIDWEST/GREAT LAKES AND A SLIGHT
COOLING TREND. RAIN CHANCES WILL DECREASE SUBSTANTIALLY AND HIGH
TEMPERATURES WILL DROP BACK INTO THE 80S BY NEXT MONDAY THROUGH
WEDNESDAY.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1250 PM CDT WED JUL 1 2026
VFR CONDITIONS ARE FORECAST TO CONTINUE ACROSS THE CENTRAL IL
AIRPORTS THROUGH 18Z/1 PM THU. ASIDE FROM A FEW HIGH/THIN
CLOUDS AND FEW-SCT DIURNAL CUMULUS CLOUDS WITH 3-5K FT BASES
TODAY AND THU, SKIES WILL REMAIN MOSTLY CLEAR. SW WINDS WILL
GUST TO AROUND 20 KTS THIS AFTERNOON BEFORE DECREASING TO LESS
THAN 10 KTS BY SUNSET AND VEERING MORE SOUTH TONIGHT. SW WINDS
NEAR 10 KTS WILL PREVAIL AFTER 15Z THU.
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...07
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