339
FXUS63 KILX 180259
AFDILX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LINCOLN IL
859 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.
UPDATE
ISSUED AT 859 PM CST SUN NOV 17 2024
UPDATES THIS EVENING TO SLOW THE ARRIVAL OF LOW CHANCES OF LIGHT
PRECIPITATION A COUPLE OF HOURS, BUT OTHERWISE FORECAST LOOKS ON
TRACK TO SPREAD WIDESPREAD RAIN INTO THE AREA NEAR SUNRISE AS
MOIST WARM ADVECTION DEVELOPS AHEAD OF AN APPROACHING LOW. THE
FIRST SPRINKLES COULD DEVELOP AS EARLY AS 1 AM. HAVE ALSO RAISED
LOWS FOR TONIGHT, AS WE HAVE LIKELY ALREADY SEEN THE LOWEST
TEMPERATURES OF THE NIGHT IN THE LOWER TO MID 50S, AND
TEMPERATURES SHOULD SUBTLY INCREASE THE REMAINDER OF THE NIGHT.
37
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 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 557 PM CST SUN NOV 17 2024
CIGS AND VSBYS WILL LOWER OVERNIGHT AS A FRONTAL ZONE STALLS OUT
OVER THE AREA AHEAD OF AN APPROACHING LOW AND INTERACTS WITH MOIST
SOUTHERLY FLOW. OBSERVATIONS WEST OF KDEC-KBMI SHOW OVERCAST CIGS
SPREADING EASTWARD AND APPROACHING MVFR LEVELS, WHICH SHOULD
OVERSPREAD CENTRAL IL OVER THE NEXT FEW HOURS. FURTHER LOWERING OF
CIGS OVERNIGHT SHOULD BE ACCOMPANIED BY RAIN SHOWERS DEVELOPING
AND BECOMING WIDESPREAD BY 11Z-15Z, ALONG WITH IFR CIGS. GRADUAL
IMPROVEMENT IN CIGS SHOULD TAKE PLACE INTO MONDAY AFTERNOON,
ALTHOUGH MVFR WILL LIKELY CONTINUE. WINDS S 4-8 KTS INITIALLY,
BECOMING SE AROUND 15 KTS OVERNIGHT. SE WINDS WILL INCREASE MONDAY
MORNING, BECOMING SE 12-16 KTS, WITH GUSTS AROUND 25 KTS BY
18Z-20Z.
37
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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