500
FXUS63 KILX 182337
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
537 PM CST WED DEC 18 2024
KEY MESSAGES
- LOW PRESSURE TRACKING FROM THE NORTHERN PLAINS TO SOUTHERN GREAT
LAKES THURSDAY AND FRIDAY WILL BRING BREEZY WEATHER TO CENTRAL
IL, ALONG WITH SCATTERED SNOW SHOWERS THURSDAY NIGHT AND
FRIDAY.
- A BRIEF SHOT OF COLDER AIR WILL AFFECT THE REGION FRIDAY AND
SATURDAY, BEFORE TEMPERATURES TURN ABOVE NORMAL NEXT WEEK.
DISCUSSION
ISSUED AT 200 PM CST WED DEC 18 2024
NEXT SHORTWAVE OF INTEREST WAS NOTED ON WATER VAPOR IMAGERY OVER
THE NORTHERN ROCKIES EARLY THIS AFTERNOON. LOW PRESSURE OVER
SOUTHERN ALBERTA IS FORECAST TO SHIFT SOUTHEAST TOWARD SOUTHERN
WI BY FRIDAY EVENING. THIS TRACK IS SLIGHTLY FARTHER NORTH THAN
WHAT WAS SHOWN 24 HOURS AGO, AND LENDS HIGHER CONFIDENCE THAT
MOST, IF NOT ALL, OF THE WARM ADVECTION PRECIP WILL REMAIN NORTH
OF OUR AREA THROUGH THURSDAY EVENING. THE INITIAL IMPACT OF THE
LOW WILL BE FELT WITH AN INCREASE IN SOUTH WINDS LATE THU MORNING
THROUGH THE AFTERNOON, GUSTING 20-25 MPH. SHORT RANGE, HIGH-RES
GUIDANCE SUPPORTS THE FARTHER NORTH LOW TRACK OF THE
REGIONAL/GLOBAL MODELS/ENSEMBLES, AND HAVE TRIMMED 20-30% POPS TO
THE FAR NORTHERN CWA (NORTH OF I-74) THU NIGHT.
GUIDANCE SHOWS A PRONOUNCED SHORTWAVE ROTATING THROUGH THE BACK
SIDE OF THE UPPER TROUGH FRIDAY MORNING, AND GIVEN STEEP LAPSE
RATES IN COLD ADVECTION FEEL SCATTERED SNOW SHOWERS WILL BE A
GOOD BET, AT LEAST FOR THE NORTHEAST HALF OF THE CWA. ANY
ACCUMULATION SHOULD BE MINOR, WITH 12Z/18TH LREF PROBS OF 0.5"
RUNNING 25% NORTH OF I-74. NORTHWEST WIND GUSTS WILL BE ANOTHER
ISSUE LATE THURSDAY NIGHT AND FRIDAY IN THE TIGHTENING MSLP
GRADIENT BEHIND THE LOW. EFFICIENT MIX-DOWN OF THE HIGHER MOMENTUM
AIR IN CAA WILL LEAD TO 25-35 MPH GUSTS, AND WIND CHILLS IN THE
TEENS TO LOWER 20S THROUGH THE DAY.
THE COOL-DOWN BEHIND THE CLIPPER WILL BE SHORT LIVED AND NOT
PARTICULARY IMPRESSIVE FOR THIS TIME OF YEAR. CURRENT BLENDED
GUIDANCE SHOWS MAXES AND MINS ONLY A COUPLE DEGREES BELOW NORMAL
FRIDAY THROUGH SATURDAY NIGHT, WITH WARM ADVECTION COMMENCING
ALREADY BY SUNDAY AFTERNOON AS SOUTH WINDS INCREASE ON THE BACK OF
SURFACE RIDGING.
QUASI-ZONAL FLOW SETS UP EARLY NEXT WEEK, AND NBM GUIDANCE OFFERS
5-10 DEGREE ABOVE NORMAL TEMPERATURES THROUGH THE FIRST HALF OF
THE WEEK. A SHORTWAVE AND ASSOCIATED FRONT RIPPLING THROUGH THE
WESTERLY FLOW WILL BRING PRIMARILY RAIN CHANCES TO THE REGION
MON/TUE.
25
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 537 PM CST WED DEC 18 2024
MVFR CIGS COVER MUCH OF THE REGION THIS EVENING, DESPITE A HOLE IN
THIS CLOUD COVERAGE OVER PORTIONS OF CENTRAL IL TO START THE 00Z
TAF PERIOD. OVER THE NEXT SEVERAL HOURS, MVFR CIGS ARE EXPECTED TO
SPREAD BACK OVER THE AREA, ALTHOUGH THE MOST UNCERTAINTY IS FOR
KSPI AND KDEC WHERE THERE IS SOME POTENTIAL CLOUD COVER WILL NOT
CONTINUE SPREADING SOUTHWARD INTO THIS AREA. AFTER THIS, IMPROVING
CONDITIONS ARE EXPECTED THURSDAY AS SOUTH-SOUTHWESTERLY FLOW
DEVELOPS, BUT VFR CIGS ARE MORE UNCERTAIN AS FAR NORTH AS I-74.
WINDS NW 6-12 KTS, BECOMING LIGHT AND VARIABLE BY 03Z-06Z, THEN
BECOMING S 10-14 KTS WITH GUSTS AROUND 20 KTS BY 17Z.
37
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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