332
FXUS63 KILX 172201
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
401 PM CST SUN NOV 17 2024
KEY MESSAGES
- RAIN ON MONDAY WILL BE ACCOMPANIED BY GUSTY WINDS. THERE IS A
MEDIUM PROBABILITY (60% CHANCE) THAT GUSTS WILL EXCEED 45 MPH
MONDAY EVENING, PRIMARILY IN AREAS WEST OF INTERSTATE 55.
- A SHARP COOL DOWN WILL ARRIVE BY MIDWEEK, SIGNALING THE RETURN
OF BELOW-NORMAL TEMPERATURES.
DISCUSSION
ISSUED AT 128 PM CST SUN NOV 17 2024
A SURFACE LOW, CURRENTLY POSITIONED OVER CENTRAL ONTARIO, HAS
FILLED AND WEAKENED WITH A DIFFUSE COLD FRONT EXTENDING FROM
ROUGHLY MILWAUKEE TO DAVENPORT TO KANSAS CITY. A NARROW BAND OF
LIGHT RAIN HAS DEVELOPED IN THE VICINITY OF THE FRONT, WITH
SPRINKLES AND PATCHY DRIZZLE BEING OBSERVED WELL OUT AHEAD OF THE
FRONT WITHIN A BROAD AREA OF WARM/ISENTROPIC ASCENT.
THE COLD FRONT WILL STALL-OUT OVER CENTRAL ILLINOIS TONIGHT AS
THE UPPER-LEVEL FORCING BECOMES DISPLACED TOO FAR EAST. WITH A
STRONG PUSH OF WARM/ISENTROPIC ASCENT IMPINGING ON THE STATIONARY
BOUNDARY, WE SHOULD SEE AREAS OF LOW STRATUS AND PATCHY DRIZZLE
DEVELOP OVERNIGHT. MODEL GUIDANCE IS THEN IN EXCELLENT AGREEMENT
OF RESURRECTING THE STATIONARY BOUNDARY AS A WARM FRONT BY MONDAY
MORNING, LIFTING IT BACK NORTHWARD AS A STRONG SHORTWAVE TROUGH
EJECTS OUT OF THE SOUTHERN ROCKIES AND KICKS OFF RAPID CYCLOGENESIS
OVER THE PLAINS. A ROBUST INFLUX OF MOISTURE SURGING NORTHWARD
FROM THE WESTERN GULF WILL ADVECT ANOMALOUS PWATS (> 1.5") INTO
CENTRAL ILLINOIS AHEAD OF THE FRONTAL SYSTEM. WITH STRONG SYNOPTIC
ASCENT JUXTAPOSED TO THE MOISTURE-LADEN AIRMASS, WE SHOULD SEE
ANOTHER BENEFICIAL RAINFALL ACROSS MUCH OF THE REGION. THE LATEST
HREF LPMM QPF GUIDANCE SUPPORTS BETWEEN 0.25"-1" IN AREAS NORTH OF
I-70.
PERHAPS MORE IMPACTFUL THAN THE RAIN WILL BE THE WIND. WITH THE
DEEPENING SURFACE LOW LIFTING ACROSS CENTRAL IOWA BY MONDAY
EVENING, WE SHOULD BEGIN TO EXPERIENCE SYNOPTIC GUSTS GREATER THAN
30 MPH. HI-RES GUIDANCE REMAINS FAIRLY BULLISH WITH PEAK GUSTS,
WITH THE DETERMINISTIC HRRR AND NAMNEST OFFERING A BROAD AREA OF
45+ MPH GUSTS ACCOMPANYING SHOWERS ALONG THE COLD FRONT MONDAY
EVENING. MODEL SOUNDINGS SUGGEST THIS MIGHT BE OVERDONE, WITH A
STABLE LAYER LIKELY LIMITING MOMENTUM TRANSFER DURING THE EVENING
HOURS. THE MORE LIKELY WINDOW FOR GUSTS EXCEEDING 45 MPH LOOKS TO
COME LATE MONDAY NIGHT INTO EARLY TUESDAY MORNING AS THE OCCLUDED
FRONT LIFTS ACROSS WEST CENTRAL ILLINOIS. BY THIS TIME, THE LOW-
LEVEL JET CORE WON'T BE QUITE AS STRONG, BUT LOW-LEVEL LAPSE RATES
APPEAR TO STEEPEN, MAKING THE BOUNDARY LAYER UNSTABLE, AND
AUGMENTING VERTICAL MOMENTUM TRANSFER. AT THIS POINT, CONFIDENCE
AND DURATION OF ENHANCED GUSTS REMAINS LOW ENOUGH TO PRECLUDE A
WIND ADVISORY, BUT WE WILL CONTINUE TO MONITOR TRENDS.
ATTENTION THEN TURNS TO WED/THU AS THE FRONTAL SYSTEM OCCLUDES AND
PHASES TOGETHER WITH ANOTHER SHORTWAVE DIGGING OUT OF THE PACIFIC
NORTHWEST. MODEL TRENDS HAVE BEEN FOR THE UPPER-LEVEL LOW TO BE
FURTHER EAST AND NOT QUITE AS DEEP, RESULTING IN A SLIGHTLY LESS
IMPACTFUL EVENT FOR CENTRAL ILLINOIS. THE CMC AND ITS ENVELOPE OF
ENSEMBLE GUIDANCE CONTINUES TO BE THE OUTLIER WITH THE COLD PUSH,
THOUGH THE ECMWF/EPS STILL HANGS ONTO A GLANCING BLOW OF COLD
TEMPERATURES LATE NEXT WEEK. AT THIS POINT WE COULDN'T RULE OUT
SOME SCATTERED SNOW SHOWERS ALONG THE I-74 CORRIDOR DURING THE
WED/THU TIMEFRAME, BUT ANYTHING IMPACTFUL CONTINUES TO TREND EAST
OF OUR AREA.
AT THIS POINT, TEMPERATURES INTO NEXT WEEKEND ARE NOT LOOKING AS
COLD EITHER. IF ANYTHING, THE DETERMINISTIC NBM APPEARS
UNREALISTICALLY COLD WITH ITS BIAS-CORRECTION SOLUTIONS COMING IN
BELOW THE 25TH PERCENTILE OF THE RAW GUIDANCE.
MJA
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1127 AM CST SUN NOV 17 2024
LIGHT SHOWERS HAVE BEEN REPORTED ACROSS THE REGIONAL TERMINALS
THIS MORNING AND EARLY AFTERNOON. THIS ACTIVITY HAS RESULTED IN
LOW VFR CEILINGS, DUE TO A PLUME OF LOW-LEVEL MOISTURE POOLING
AHEAD OF WEAK COLD FRONT. THESE CEILINGS WILL LIKELY PERSIST
THROUGH MUCH OF THE EVENING WITH OCCASIONAL SPRINKLES OR EVEN
DRIZZLE, PERHAPS RESULTING IN BROKEN MVFR CEILINGS BY 00Z, THOUGH
CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE IN THE WRITTEN TAFS.
A MORE DEFINITIVE PUSH OF MVFR CEILINGS ARRIVE BY (OR JUST PRIOR)
TO 06Z AS THE COLD FRONT MOVES IN AND STALLS OUT OVER THE REGIONAL
TERMINALS. CONDITIONS WILL THEN GRADUALLY DETERIORATE BETWEEN
06Z-12Z WITH CEILINGS LOWERING INTO THE IFR/LIFR RANGE BEYOND 12Z
AS RAIN SPREADS IN FROM THE SOUTH.
MJA
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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