395
FXUS63 KILX 282331
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
631 PM CDT THU AUG 28 2025
KEY MESSAGES
- THERE IS A VERY LOW (10%) CHANCE CENTRAL AND SOUTHEAST ILLINOIS
EXCEEDS 1 INCH OF RAINFALL OVER THE NEXT 7 DAYS, AND ONLY A
MEDIUM (40%) CHANCE OF EXCEEDING ONE-QUARTER INCH. SOURCE(S):
NBM (13Z) AND LREF (00Z) QPF.
- THERE IS A LOW (20%) CHANCE FOR THUNDERSTORMS NEXT WEDNESDAY, AND
SEVERE WEATHER IS NOT ANTICIPATED AT CURRENT TIME.
- AT LEAST SOME SIGNAL FOR NEAR-RECORD LOW TEMPERATURES IS
EMERGING FOR LATE NEXT WEEK, PARTICULARLY IN THE
THURSDAY/FRIDAY TIMEFRAME.
DISCUSSION
ISSUED AT 1228 PM CDT THU AUG 28 2025
A ROBUST MID-LEVEL SHORTWAVE TROUGH IS CURRENTLY OBSERVED DIGGING
INTO THE EASTERN GREAT LAKES REGION, ACCOMPANIED BY A BACKDOOR
COLD FRONT PROGRESSING SOUTHWARD ALONG THE I-80 CORRIDOR. WHILE
THE LATEST HREF GUIDANCE INDICATES A LOW (10-30%) PROBABILITY OF
SCATTERED SHOWERS THIS AFTERNOON, PARTICULARLY IN AREAS NEAR AND
NORTH OF I-74, THE EXPECTATION IS FOR A MORE PREVALENT INCREASE IN
MID-LEVEL CLOUDINESS AND ONLY A FEW SPRINKLES. THIS IDEA IS
INFLUENCED BY POOR LOW-LEVEL MOISTURE, AS EVIDENCED BY THE 12Z
KILX RAOB, AND RELATIVELY WEAK FORCING (SFC CONVERGENCE) ALONG THE
FRONT.
THE COLD FRONT WILL SETTLE SOUTH OF THE REGION OVERNIGHT, WITH
SURFACE HIGH PRESSURE BUILDING INTO THE GREAT LAKES REGION FOR
FRIDAY. DRY, MILD AND OTHERWISE LOW-IMPACT WEATHER WILL THEN
EXTEND THROUGH AT LEAST MONDAY AS CENTRAL ILLINOIS FINDS ITSELF
POSITIONED BENEATH AN ATMOSPHERIC BLOCKING PATTERN. THE AVERAGE
TEMPERATURE THROUGH THE HOLIDAY WEEKEND WILL RANGE 3-5 DEGREES F
COOLER THAN WHAT IS CONSIDERED NORMAL FOR LATE AUGUST AND EARLY
SEPTEMBER, WITH DAILY HIGHS NEAR 80 AND OVERNIGHT LOWS IN THE MID
50S.
A NOTABLE PATTERN CHANGE BEGINS TO TAKE SHAPE BETWEEN TUESDAY AND
THURSDAY AS THE POLAR JETSTREAM BUCKLES OVER THE CANADIAN PRAIRIES
AND SENDS A DIGGING TROUGH SOUTHWARD INTO THE GREAT LAKES REGION.
THIS TROUGH AND ITS ATTENDANT COLD FRONT WILL MARK THE RETURN OF
SHOWER AND THUNDERSTORM CHANCES (30%) FOR CENTRAL ILLINOIS.
FOR SOME ADDED COMMENTARY INTO THE MIDDLE OF NEXT WEEK, IT IS
WORTH MENTIONING A DISLOCATION BETWEEN THE LATEST GLOBAL
DETERMINISTIC OUTPUT (GFS, ECMWF, CMC) VERSUS THE BLENDED/ENSEMBLE
OUTPUT (NBM, ECMWF AIFS). GLOBAL MODELS (SCENARIO A) SUGGEST A
FASTER AND DEEPER PROGRESSION OF THE UPPER-LEVEL TROUGH INTO THE
GREAT LAKES BY LATE WEDNESDAY INTO THURSDAY. CONVERSELY,
BLENDED/ENSEMBLE GUIDANCE (SCENARIO B) INDICATES A SLOWER,
SHALLOWER EVOLUTION OF THE UPPER TROUGH, LARGELY KEEPING THE COLD
CORE NORTHWARD IN ONTARIO. REGARDLESS, BOTH SCENARIOS PREDICT AT
LEAST ONE, IF NOT MULTIPLE, COLD FRONTS MOVING THROUGH CENTRAL
ILLINOIS NEXT WEEK. IN EITHER CASE, THE MOISTURE FLUX AHEAD OF THE
FRONT APPEARS LIMITED, ORIGINATING FROM THE PACIFIC RATHER THAN
THE GULF, SO SIGNIFICANT RAINFALL IS NOT ANTICIPATED. THE PRIMARY
DIFFERENCES BETWEEN SCENARIO A AND SCENARIO B INVOLVE THE SHEAR
AND FORCING PRECEDING THE FRONT, AS WELL AS THE TEMPERATURES
FOLLOWING IT. IF SCENARIO A UNFOLDS, CENTRAL ILLINOIS COULD SEE
MORE ORGANIZED CONVECTION MID-NEXT WEEK, FOLLOWED BY CHILLY
OVERNIGHT LOWS BY THE END OF THE WEEK. SOME GLOBAL MODELS (GFS AND
ECMWF) ARE FORECASTING SURFACE DEW POINTS IN THE LOW 30S FOR NEXT
THURSDAY NIGHT, WHICH COULD HELP US CHALLENGE RECORD LOW
TEMPERATURES.
MJA
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 631 PM CDT THU AUG 28 2025
A COLD FRONT IS IN THE PROCESS OF DROPPING SOUTH THROUGH THE AREA
THIS EVENING. A FEW SHOWERS HAVE DEVELOPED ALONG IT, WITH A LOW
CHANCE (20%) THAT ACTIVITY IMPACTS KPIA AND KBMI. ALTHOUGH VFR
CONDITIONS ARE EXPECTED THE MAJORITY OF THE TAF PERIOD, THERE IS A
LOW CHANCE FOR MVFR CEILINGS AND/OR VISIBILITY REDUCTIONS AS THE
FRONT PASSES LATE TONIGHT. WINDS WILL BE OUT OF THE WEST-NORTHWEST
AND THEN GRADUALLY VEER TO THE NORTHEAST OVERNIGHT BEHIND THE
FRONT.
NMA
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page