009
FXUS63 KILX 130538
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1238 AM CDT THU AUG 13 2026
KEY MESSAGES
- OCCASIONAL THUNDERSTORMS ARE EXPECTED THE NEXT FEW DAYS. SOME
OF THESE STORMS MAY BE SEVERE, WITH LOCALLY DAMAGING WINDS, A
FEW TORNADOES POSSIBLE, AND ISOLATED LARGE HAIL.
- DANGEROUS HEAT REMAINS A CONCERN THROUGH THE WEEKEND,
ESPECIALLY ACROSS SOUTHERN PORTIONS OF CENTRAL IL, AS
AFTERNOON HEAT INDEX VALUES APPROACH 105 DAILY UNLESS
THUNDERSTORM ACTIVITY DISRUPTS AFTERNOON HEATING.
- A COLD FRONT ARRIVING SUNDAY LOOKS TO BRING RELIEF FROM THE
HEAT FOR AT LEAST A FEW DAYS BY MONDAY.
DISCUSSION
ISSUED AT 251 PM CDT WED AUG 12 2026
SHOWERS AND A FEW THUNDERSTORMS REMAIN OVER PORTIONS OF CENTRAL AND
SOUTHEAST IL WHICH RESIDES IN A RELATIVELY STATIONARY FRONTAL ZONE.
WITH A COMPLEX OF STRONG THUNDERSTORMS THAT PUSHED EASTWARD ALONG
ROUGHLY THE I-74 CORRIDOR THIS MORNING, AN OUTFLOW PUSHED SOUTHWARD
ACROSS MUCH OF THE AREA WITH COOLER AIR AND CLOUD COVER TEMPERING
INSTABILITY ACROSS MUCH OF THE AREA. HOWEVER, SPC MESOANALYSIS
INDICATES STRONG MLCAPE AROUND 4000 J/KG LINGERING SOUTH OF I-70.
ANOTHER SHORTWAVE IMPULSE CURRENTLY INITIATING THUNDERSTORMS NEAR
WESTERN PORTIONS OF I-72 IS SHOWING EFFECTIVE BULK SHEAR OF 40-50
KTS AND COULD DRIVE ANOTHER COMPLEX OF SEVERE STORMS AS MOVES OVER
THAT AREA THIS EVENING. SPC MAINTAINS A SLIGHT RISK FOR SEVERE
STORMS IN EAST-CENTRAL AND SOUTHEAST IL, WITH DAMAGING WIND AS THE
HIGHEST PROBABILITY FOR SEVERE WEATHER (15% RISK), BUT ALSO A 2%
TORNADO RISK AND 5% HAIL RISK.
TONIGHT, MOST MODELS HAVE A RELATIVE LULL IN THUNDERSTORM ACTIVITY
DESPITE A FEW STORMS DEVELOPING OVER THE STALLED FRONTAL BOUNDARY,
HOWEVER ANOTHER NOCTURNAL MCS LOOKS TO BE MOVING ACROSS IA
OVERNIGHT, HEADING TOWARD NORTHERN OR CENTRAL IL THURSDAY MORNING.
HIGH-RES ENSEMBLES DEPICT 1000-200 J/KG MUCAPE OVERLAPPING 30-40 KT
DEEP LAYER BULK SHEAR AND 100-200 SRH, AND ADDITIONAL SEVERE STORMS
WILL BE POSSIBLE, FOR WHICH SPC DEPICTS A MARGINAL RISK. THE PATTERN
WILL CONTINUE THROUGH FRIDAY IF NOT SATURDAY AS WELL.
ON SUNDAY, A COLD FRONT WILL TRAVERSE THE AREA DRIVEN BY A MORE
POTENT SHORTWAVE MOVING THROUGH THE NORTHERN STATES. ADDITIONAL
SHOWERS AND THUNDERSTORMS MAY ACCOMPANY THIS FRONTAL PASSAGE, THEN A
QUIETER PERIOD SHOULD ENSUE FOR EARLY NEXT WEEK.
HIGHS WILL RANGE FROM 80S TO LOWER 90S, WITH DEWPOINTS WELL INTO THE
70S, YIELDING AFTERNOON HEAT INDEX VALUES APPROACHING 105 DAILY FOR
PORTIONS OF CENTRAL AND SOUTHEAST IL, ESPECIALLY SOUTHERN PORTIONS.
HOWEVER, THUNDERSTORM ACTIVITY WILL GREATLY INFLUENCE TEMPERATURES
AND HEAT INDEX, AND PREDICTABILITY OF HEAT INDEX REMAINS LOW. HIGHS
LOOK TO REACH ONLY INTO THE 80S FOR EARLY NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1238 AM CDT THU AUG 13 2026
A CHALLENGING FORECAST OVER THE NEXT 24 HOURS CHARACTERIZED BY FOG,
LOW STRATUS, AND PERIODS OF SHOWERS AND STORMS. CIRRUS CONTINUES TO
CLEAR FROM WEST TO EAST LATE TONIGHT WITH LIGHT SURFACE WINDS IN
PLACE NORTH OF A SURFACE BOUNDARY. MVFR TO IFR FOG/LOW STRATUS
WILL EXPAND THROUGH EARLY MORNING WITH THE WORST CONDITIONS
EXPECTED NEAR AND NORTH OF THE I-74 CORRIDOR. VISIBILITY SHOULD
IMPROVE BETWEEN 12- 14Z, THOUGH CEILINGS AT NORTHERN TERMINALS
WILL REMAIN MVFR FOR AT LEAST THE FIRST HALF OF THE DAY.
A THUNDERSTORM COMPLEX WILL RACE THROUGH NORTH-CENTRAL PARTS OF IL
FROM MID-MORNING TO EARLY AFTERNOON, WITH THE HIGHEST PROBABILITIES
OF TSRA AT KPIA AND KBMI. PROB30 GROUPS ARE NOTED AT THE REMAINING
SITES WHERE CONFIDENCE REMAINS LOWER. ADDITIONAL STORMS ARE POSSIBLE
NEAR/NORTH OF I-74 LATE THURSDAY NIGHT WITH PROB30 GROUPS ADDED FOR
THIS POTENTIAL. EASTERLY WINDS WILL LARGELY REMAIN IN PLACE THROUGH
THE PERIOD, WITH THE DIRECTION MORE VARIABLE WITH ANY STORM
ACTIVITY.
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM NOON TODAY TO 8 PM CDT SUNDAY FOR
ILZ066>068-071>073.
KEY MESSAGES...37
DISCUSSION...37
AVIATION...NMA
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