694
FXUS63 KILX 182000
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
200 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 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1111 AM CST WED DEC 18 2024
TRICKY TAFS WITH RESPECT TO CEILING CATEGORY OVER THE NEXT 24
HOURS. CURRENTLY IFR HANGING ON FOR MOST CENTRAL IL TERMINALS,
THOUGH THESE WILL RISE TO MVFR EARLY THIS AFTERNOON. SATELLITE
TRENDS UPSTREAM (NORTHWEST) INDICATE PLENTY OF HOLES IN THE
OVERCAST, BUT PREDOMINANT MVFR CEILINGS INTO MN. GIVEN TYPICAL
TRENDS IN THE COOL SEASON, OPTED TO BE PESSIMISTIC WITH MVFR
CEILINGS FORECAST INTO THU MORNING, THOUGH PERIODS OF VFR WILL
LIKELY BE PRESENT THROUGH TONIGHT. NORTHWEST WINDS AT 10-14 KT
THIS AFTERNOON WILL PERIODICALLY GUST AROUND 20 KT, BEFORE GOING
LIGHT/VARIABLE LATER THIS EVENING AS HIGH PRESSURE MOVES OVERHEAD.
S/SSE WINDS TO INCREASE LATE THU MORNING AS THE MSLP GRADIENT
INCREASES ON THE BACK SIDE OF THE RIDGE.
25
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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