491
FXUS63 KILX 212327
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
627 PM CDT WED OCT 21 2026
KEY MESSAGES
- SUNNY MILD DAYS AND COOL NIGHTS PERSIST ACROSS CENTRAL AND
SOUTHEAST ILLINOIS THROUGH SUNDAY, WITH HIGHS IN THE MID-
UPPER 70S AND LOWS IN THE 40S.
- A COLD FRONT MOVES ACROSS THE REGION EARLY NEXT WEEK, BRINGING
PROSPECTS FOR LIGHT RAIN, FOLLOWED BY COOLER TEMPERATURES.
DISCUSSION
ISSUED AT 1211 PM CDT WED OCT 21 2026
SURFACE RIDGE AXIS CENTERED ACROSS THE AREA PROVIDES QUIET,
CLEAR CONDITIONS ACROSS CENTRAL AND SOUTHEAST ILLINOIS. DRY AIR
AND SUBSIDENCE WILL CONTINUE TO PRODUCE MAINLY CLEAR SKIES AND
LARGE DIURNAL TEMPERATURE SWINGS OVER THE NEXT SEVERAL DAYS.
MID-LEVEL HEIGHTS BUILD ACROSS THE MISSISSIPPI VALLEY FRIDAY
AND THIS WEEKEND AS THE SURFACE HIGH SLIPS FARTHER EAST. MODELS
SHOW STRONG CONSENSUS ON ESTABLISHING PERSISTENT SOUTHERLY
RETURN FLOW. 850-HPA TEMPERATURES IN THE LOWER TEENS C, ALONG
WITH DEEPER MIXING SUPPORT AFTERNOON HIGHS AROUND 80F ON
SUNDAY, AROUND 15 DEGREES ABOVE CLIMATOLOGICAL AVERAGES.
MEDIUM-RANGE DETERMINISTIC SOLUTIONS (ECMWF, ECMWF-AI, AND GFS)
AND THE ENSEMBLE SUITE DIVERGE EARLY NEXT WEEK REGARDING THE
PROGRESSION OF AN UPSTREAM LONGWAVE TROUGH AND ASSOCIATED
SURFACE COLD FRONT. THE DETERMINISTIC GFS EXHIBITS A FASTER
FRONTAL TRANSIT ACROSS CENTRAL ILLINOIS MONDAY EVENING WITH
STRONGER PRE-FRONTAL 850-HPA FLOW (4050 KT). CONVERSELY, THE
ECMWF AND ECMWF-AI ARE ROUGHLY 6 TO 12 HOURS SLOWER, MAINTAINING
A BROADER FRONTAL STRUCTURE AND TRACKING THE PRIMARY BOUNDARY
THROUGH THE FORECAST AREA TUESDAY. GEFS AND ECMWF ENSEMBLE
MEMBERS FAVOR THIS SLOWER PROGRESSION. LATEST NBM RUN HAS
LOWERED POPS BELOW MENTIONABLE LEVELS, BUT THIS WILL LIKELY
CHANGE AS THE SYSTEM DEVELOPS. BEHIND THE FRONT, A SHOT OF
COOLER AIR WILL MOVE IN, RETURNING TEMPERATURES TO MORE
SEASONABLE LEVELS TUE-WED.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 627 PM CDT WED OCT 21 2026
HIGH PRESSURE WILL PRODUCE MOSTLY CLEAR SKIES AND LIGHT WINDS
FOR THE UPCOMING 24 HOURS, WITH VFR CONDITIONS PREVAILING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...37
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