059
FXUS63 KILX 202022 CCA
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
221 PM CST FRI DEC 20 2024
KEY MESSAGES
- SEASONABLY COLD THROUGH SATURDAY, THEN TURNING MILD. THE AVERAGE
TEMPERATURE NEXT WEEK WILL RUN ABOUT 10 DEGREES WARMER THAN
WHAT IS CONSIDERED NORMAL FOR LATE DECEMBER.
- CHOPPY ATMOSPHERIC FLOW WILL BRING FORTH MULTIPLE CHANCES FOR
LIGHT RAIN THROUGHOUT NEXT WEEK.
DISCUSSION
(THROUGH NEXT FRIDAY)
ISSUED AT 1231 PM CST FRI DEC 20 2024
THE MAIN FORECAST CHALLENGES THIS EVENING INVOLVE CLOUD COVER AND
OVERNIGHT TEMPS. UPSTREAM OBSERVATIONS ACROSS NORTHERN IL AND
SOUTHEAST IA REVEAL QUITE A BIT OF CLEARING, AND THIS MAKES SENSE
AS A DRIER/SUBSIDENT AIRMASS MOVES IN BEHIND THE DEPARTING UPPER-
LEVEL SHORTWAVE TROUGH. WHILE MODEL GUIDANCE IS IN FAIRLY GOOD
AGREEMENT THAT LOW CLOUDS WILL CLEAR OVERNIGHT, THERE REMAINS SOME
MINOR DIFFERENCES ON EXACTLY WHEN, AS WELL AS THE EASTERN EXTENT
OF CLEARING. WITH N/NE LOW-LEVEL WINDS IN PLACE TONIGHT, THERE
COULD BE A SHALLOW PLUME OF MOISTURE/CLOUDS BENEATH THE INVERSION
THAT ADVECTS IN FROM LAKE MICHIGAN. THE LATEST HREF GUIDANCE
SUPPORTS GREATER THAN A 70% CHANCE FOR CLOUDS WITH BASES BELOW 3
KFT TO STICK AROUND THROUGH 09Z/3AM IN AREAS EAST OF A CHAMPAIGN
TO CHARLESTON LINE. THE HIGHEST PROBABILITIES WILL COME ALONG THE
IL/IN STATE LINE.
AS FAR AS TEMPERATURES GO TONIGHT, THEY WILL BE IMPACTED BY NOT
ONLY CLOUD COVER BUT ALSO SNOWPACK. MOST SHORT RANGE GUIDANCE
SUPPORTS OVERNIGHT LOWS AROUND 20 DEGF, THOUGH IT WOULD BE
REASONABLE FOR LOCATIONS WITH A FRESH SNOWPACK AND CLEAR SKIES TO
DIP DOWN INTO THE MID TEENS. AREAS NORTH OF PEORIA TO PARIS LINE
COULD FIT THIS BILL.
CONDITIONS THEN REMAIN DRY AND SEASONABLY COLD THROUGH SATURDAY
AS A RIDGE OF HIGH PRESSURE QUICKLY BUILDS ACROSS THE MIDWEST.
THE PATTERN BECOMES MORE MILD BY SUNDAY AS BREEZY SOUTHERLY WINDS
INCREASE AHEAD AN AREA OF DEVELOPING LOW PRESSURE. AFTERNOON
TEMPERATURES WILL WARM INTO UPPER 30S BY SUNDAY, AND MID-TO-UPPER
40S BY MONDAY AHEAD OF THE COLD FRONT. MOISTURE RETURN AHEAD OF
FRONTAL PASSAGE IS FAIRLY LIMITED, WITH MID-LEVEL DRY AIR KEEPING
QPF BELOW 0.10".
DESPITE COLD FRONTAL PASSAGE ON MONDAY, MILD TEMPERATURES WILL
REMAIN IN PLACE THROUGH THE REMAINDER OF NEXT WEEK AS A PAIR OF
UPPER- LEVEL SHORTWAVE TROUGHS DIG INTO THE SOUTHERN PLAINS AND
THEN LIFT/PIVOT ACROSS THE OHIO VALLEY. PLENTY OF WARM/MOIST GULF
AIR WILL BE WRAPPED INTO THESE DISTURBANCES, PROPPING TEMPERATURES
UP INTO THE 50S BY THE BACK HALF OF NEXT WEEK WHILE SUPPORTING
MULTIPLE CHANCES FOR RAIN. WITH CENTRAL ILLINOIS POSITIONED ON THE
NORTHERN FRINGE OF THESE DISTURBANCES, AT LEAST FOR NOW, QPF
AMOUNTS ARE CURRENTLY LESS THAN 0.25" THROUGH NEXT WEEK.
MJA
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1124 AM CST FRI DEC 20 2024
UPSTREAM OBSERVATIONS ACROSS NORTHERN ILLINOIS INDICATE A STEADY
IMPROVEMENT TO VFR THIS AFTERNOON AS A DRIER/SUBSIDENT AIRMASS
WORKS IN FROM THE NORTH. THE EXCEPTION COULD BE AT BMI/CMI WHERE
MVFR CEILINGS COULD LINGER A LITTLE LONGER INTO THIS EVENING AS
N/NE WINDS STEER SOME SHALLOW MOISTURE/CLOUDS FROM LAKE MICHIGAN
INTO EASTERN ILLINOIS. HAVE OPTED TO SCATTER MVFR CEILINGS AT
BMI BY 21Z AND CMI BY 23Z DESPITE MODEL TRENDS CLEARING BOTH
TERMINALS TO VFR.
OTHERWISE, WINDS WILL STEADILY DIMINISH THIS EVENING AS SURFACE
LOW PRESSURE DEPARTS THE REGION, AND WE WILL BE LEFT WITH LIGHT
NORTHERLY WINDS GOING INTO SATURDAY MORNING.
MJA
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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