567
FXUS63 KILX 182303
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
503 PM CST SAT JAN 18 2025
KEY MESSAGES
- FRIGID AIR MOVES IN TONIGHT AND WILL PERSIST THROUGH WEDNESDAY
MORNING. LOW TEMPERATURES ARE EXPECTED TO RANGE FROM 5 DEGREES
ABOVE OR BELOW ZERO EACH NIGHT SUNDAY THROUGH TUESDAY.
- WIND CHILL VALUES WILL FALL BELOW ZERO BY SUNDAY MORNING, AND WITH
THE EXCEPTION OF THE DAYTIME HOURS ON MONDAY, LIKELY STAY BELOW ZERO
IN MOST AREAS THROUGH TUESDAY NIGHT. MINIMUM WIND CHILL VALUES OF 10
TO 20 BELOW ZERO DEGREES WILL BE COMMON NORTH OF I-72, WITH VALUES
OF 5 TO 15 BELOW COMMON SOUTH OF I-72.
DISCUSSION
ISSUED AT 219 PM CST SAT JAN 18 2025
THE PRIMARY WEATHER HAZARD THROUGH THE MIDDLE OF NEXT WEEK IS A
STRETCH OF BITTER COLD CONDITIONS. AS OF SATURDAY AFTERNOON, RAP
ANALYSIS SHOWED A STRONG, 1046-MB SFC HIGH PRESSURE JUST NORTH OF
THE MONTANA BORDER, WHILE A 989-MB SFC LOW WAS LOCATED NORTHEAST
OF THE HUDSON BAY, WITH AN EXPANSIVE COLD FRONT DRAPED SOUTHWARD
FROM THERE, APPROACHING THE EASTERN APPALACHIANS. THE SFC HIGH
WILL SLOWLY SHIFT SOUTHEAST, BUT THIS SFC PATTERN WILL SUPPORT THE
PRESENCE OF A PERSISTENT TIGHT PRESSURE GRADIENT ACROSS IL, WHICH
WILL KEEP BREEZY NORTHWEST WINDS IN PLACE. CONTINUED COLD AIR
ADVECTION WILL PUSH A VERY COLD, ARCTIC AIR MASS BEING IN PLACE BY
MIDDAY SUNDAY, WITH MOST DETERMINISTIC MODELS SUGGESTING 850MB
TEMPS BETWEEN -20 AND -25 DEGC, WHICH IS WELL BELOW THE 10TH
PERCENTILE OF THE ILX OBSERVED SOUNDING CLIMATOLOGY (-15 DEGC).
FOR TONIGHT, THE COLDEST CONDITIONS ARE EXPECTED IN AREAS
NORTHWEST OF THE IL RIVER VALLEY, WHERE TEMPS FALL INTO THE LOW
SINGLE DIGITS AND NORTHWEST WINDS REMAIN SUSTAINED AROUND 15-20
MPH. THE LATEST HREF GUIDANCE INDICATES THERE IS A 60-80% CHANCE
THAT WIND CHILL VALUES FALL BELOW OUR COLD WEATHER ADVISORY
CRITERIA (-15 DEGF FOR THOSE COUNTIES). DAYTIME HIGHS WILL BE
SIGNIFICANTLY BELOW NORMAL, AND THIS IS DESPITE THE FACT THAT WE
ARE CLIMATOLOGICALLY AT THE COOLEST POINT OF THE WINTER SEASON.
NORMAL HIGH TEMPS ARE RIGHT AROUND FREEZING THIS TIME OF YEAR. THE
FORECAST HIGH TEMPS DON'T QUITE THREATEN RECORD COLD HIGHS,
HOWEVER, WHICH ARE AT OR BELOW ZERO FOR PEORIA.
TEMPS TURN EVEN COLDER BY SUN NIGHT, WITH LOWS AROUND OR SLIGHTLY
BELOW ZERO, ALTHOUGH WINDS WILL BE LIGHTER (BUT NOT CALM) DURING
THE SUNDAY NIGHT-MONDAY MORNING PERIOD. THE NET RESULT IS THAT
FORECAST MINIMUM WIND CHILL VALUES ARE FORECAST TO BE AROUND OUR
COLD WEATHER ADVISORY CRITERIA FOR A GOOD CHUNK OF THE CWA
(CRITERIA VALUES ARE - 15 DEGF FOR COUNTIES ALONG AND NORTH OF
I-72, AND -10 DEGF SOUTH OF I-72). THE LATEST HREF HAS A 60-90%
CHANCE OF -10 WIND CHILL VALUES SOUTH OF I-72, WITH A 50-90%
CHANCE OF -15 WIND CHILL VALUES FROM CANTON TO DECATUR AND NORTH.
THESE AREAS WERE ALL INCLUDED IN A COLD WEATHER ADVISORY FOR
SUNDAY NIGHT INTO MONDAY. THE GREATEST UNCERTAINTY IN REGARDS TO
NEEDING AN ADVISORY WAS IN MASON, MENARD, AND SANGAMON COUNTIES,
WHERE THE PROBABILITY OF WIND CHILLS BELOW - 15 DEGF WAS JUST 40%.
BUT RATHER THAN SPLIT HAIRS, OPTED TO INCLUDE THESE COUNTIES IN
THE COLD WEATHER ADVISORY AS WELL.
CONDITIONS DO "MODERATE" A TAD DURING THE DAY ON MONDAY, WITH
HIGHS IN THE TEENS AND WIND CHILL VALUES RISING 10-15 DEGREES
ABOVE ADVISORY CRITERIA DURING THE DAY. THUS, THE COLD WEATHER
ADVISORIES ISSUED BY OUR OFFICE ARE SET TO EXPIRE BY MID-MORNING
MONDAY. THIS WON'T BE THE END OF THE COLD, HOWEVER, WITH TWO MORE
BITTER COLD NIGHTS ANTICIPATED (MON NIGHT AND TUES NIGHT).
BY WEDNESDAY, THE CENTER OF THE SFC HIGH PRESSURE IS PROGGED TO
PUSH EAST OF ILLINOIS, SWINGING SFC WINDS AROUND TO SOUTHERLY AND
RELEASING THE REGION FROM THE GRIP OF THE ARCTIC AIR. HIGH TEMPS
CLIMB BACK TO NEAR NORMAL (LOW/MID 30S) BY THURS/FRI. GUIDANCE
DOES SUGGEST A CLIPPER-STYLE SHORTWAVE TROUGH DIGGING TOWARDS THE
AREA WED NIGHT INTO THURS, BUT FLOW NEAR THE GULF COAST IS
DIRECTED OFFSHORE AT THIS TIME, LIMITING MOISTURE ADVECTION INTO
OUR AREA AHEAD OF THIS SYSTEM. ENSEMBLE MEAN PWAT VALUES ARE QUITE
LOW, ONLY AROUND 0.25", SO MEANINGFUL PRECIPITATION CURRENTLY
APPEARS UNLIKELY OUT OF THIS WAVE, AND THE LATEST BLENDED FORECAST
HAS POPS LESS THAN 10% THROUGH THE UPCOMING WORK WEEK.
ERWIN
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 503 PM CST SAT JAN 18 2025
MVFR CEILINGS ARE HANGING ON AT KDEC-KCMI, BUT THESE SHOULD SHIFT
SOUTH AND DISSIPATE BY 00Z. SCT/BKN MID LEVEL (VFR) CLOUDS WILL
THEN DOMINATE THE CENTRAL IL TERMINALS THROUGH THE FORECAST. NNW
WINDS AT 12-15 KT OVERNIGHT WILL OCCASIONALLY GUST NEAR 20 KT. BY
EARLY MORNING WINDS ARE FORECAST TO BACK SLIGHTLY NORTHWEST WITH
GUSTS BECOMING MORE FREQUENT AND INCREASING NEAR 25 KT. THESE
GUSTS ARE EXPECTED TO CONTINUE THROUGH SUN AFTERNOON.
25
ILX WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY FROM 3 AM SUNDAY TO NOON CST MONDAY FOR
ILZ027>030-036.
COLD WEATHER ADVISORY FROM 6 PM SUNDAY TO NOON CST MONDAY FOR
ILZ031-037-038-041>046-048-051>057-061>063-066>068-071>073.
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