550
FXUS63 KILX 170443
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
1043 PM CST SAT NOV 16 2024
KEY MESSAGES
- RAIN AND GUSTY WINDS WILL OVERSPREAD THE REGION ON MONDAY. THE
RAINFALL FORECAST IS GENERALLY BETWEEN 0.25" - 1", AND WE ARE
ANTICIPATING 30-40 MPH WIND GUSTS BY MONDAY EVENING.
- A POWERHOUSE AUTUMN STORM SYSTEM WILL PUSH INTO THE REGION
WEDNESDAY AND THURSDAY, BRINGING GUSTY WINDS (30-40 MPH) AND
SHOWERY PRECIPITATION (40-60% CHANCE).
- MUCH COLDER TEMPERATURES ARRIVE THURSDAY - SATURDAY WITH SUB-
FREEZING OVERNIGHT LOWS LIKELY (> 60% CHANCE) AT SOME POINT
DURING THIS STRETCH.
UPDATE
ISSUED AT 858 PM CST SAT NOV 16 2024
MOIST WARM ADVECTION HAS BEEN PRODUCING MID LEVEL CLOUD COVER NEAR
THE MISSISSIPPI VALLEY THIS EVENING AHEAD OF A FRONTAL ZONE
STRETCHING FROM MN TO WEST TX. ALTHOUGH SOME WEAK ECHOES HAVE BEEN
DETECTED ON RADAR, SURFACE OBSERVATIONS INDICATE MOST OR ALL OF
THIS ISN'T REACHING THE GROUND, ESPECIALLY FARTHER EAST INTO WEST
CENTRAL IL. NEVERTHELESS, THIS BAND OF ECHOES LOOKS TO KEEP
SHIFTING EASTWARD OVERNIGHT, AND SHOULD RESULT IN AT LEAST A
POTENTIAL FOR SPRINKLES REACHING AS FAR EAST AS I-55 AS ADDITIONAL
MOISTURE CONTINUES TO ADVECT INTO THE AREA. CLOUD COVER HAS BEEN
MORE SPARSE THAN EXPECTED IN EASTERN IL SO HAVE DECREASED SKY
COVER THERE. BREEZY SOUTH WINDS AROUND 10 MPH WILL CONTINUE ACROSS
THE AREA TONIGHT. OTHERWISE, LOWS STILL APPEAR TO BE ON TRACK FOR
MID 40S TONIGHT, WITH THE LOWEST READINGS LIKELY EAST OF I-57
WHERE CLEARER SKIES AND LIGHTER WINDS ARE MORE PREVALENT.
37
DISCUSSION
ISSUED AT 149 PM CST SAT NOV 16 2024
AFTERNOON WATER VAPOR IMAGERY CURRENTLY DEPICTS TWO AREAS OF
INTEREST: (1) A SHORT-WAVE TROUGH MOVING ACROSS THE BLACK HILLS,
AND (2) A DEEP TROUGH DIGGING INTO BAJA CALIFORNIA. WHILE BOTH
WAVES WILL BE RESPONSIBLE FOR BRINGING SENSIBLE WEATHER TO
CENTRAL ILLINOIS, THE LATTER IS EXPECTED TO BE MORE IMPACTFUL IN
THE WEEK AHEAD.
BY LATE TONIGHT, A PRE-FRONTAL SURFACE TROUGH AND TRAILING COLD
FRONT ASSOCIATED WITH THE NORTHERN TRACK SHORTWAVE WILL MOVE
ACROSS THE MID-MISSISSIPPI VALLEY. A PLUME OF LOW-LEVEL MOISTURE
AND WEAK ISENTROPIC ASCENT AHEAD OF THIS FEATURE COULD RESULT IN
A FEW SPRINKLES SUNDAY MORNING WEST OF I-55. SOME GUIDANCE (E.G.
RAP & NAM) SUPPORTS SPRINKLES THROUGH MUCH OF THE DAY ON SUNDAY AS
THE COLD FRONT PUSHES INTO CENTRAL ILLINOIS AND STALLS OUT.
WHATEVER PRECIP WE'RE ABLE TO SQUEEZE OUT SUNDAY, IT'S GOING TO
HAVE TO BE FROM LOW- LEVEL PROCESSES, WITH THE UPPER FORCING
SAILING WELL OUT OF OUR AREA.
ATTENTION THEN QUICKLY TURNS TO MONDAY AS THE SOUTHERN STREAM
TROUGH LIFTS ACROSS THE SOUTHERN ROCKIES AND PIVOTS INTO THE
PLAINS. STRONG TEMPERATURE ADVECTION ASSOCIATED WITH THIS
DISTURBANCE WILL INCREASE BAROCLINIC INSTABILITY AND RESULT IN
RAPID CYCLOGENESIS THROUGHOUT MONDAY. WHILE THE MAIN IMPACT FROM
THIS SYSTEM, AT LEAST FOR CENTRAL ILLINOIS, APPEARS TO BE GUSTY
WINDS, THERE WILL BE WIDESPREAD RAINFALL AS WELL. A ROBUST INFLUX
OF SUB-TROPICAL MOISTURE SURGING NORTHWARD FROM THE WESTERN GULF
WILL HELP BRING 1.5" PWATS INTO CENTRAL ILLINOIS, WHICH EXCEEDS
THE 99TH PERCENTILE OF AVAILABLE MOISTURE FOR MID-NOVEMBER
CLIMATOLOGY. WITH STRONG SYNOPTIC LIFT (JET DYNAMICS) JUXTAPOSED
TO A MOISTURE-LADEN AIRMASS, WE SHOULD BE ABLE TO TAKE ANOTHER
HEALTHY BITE OUT OF OUR DROUGHT. WITH HI-RES GUIDANCE NOT OUT FAR
ENOUGH TO RESOLVE THIS FRONTAL SYSTEM, WE ARE RELYING ON NBM AND
LREF GUIDANCE FOR OUR RAINFALL GOALPOSTS (10TH-90TH PERCENTILE),
WHICH LOOK TO FALL BETWEEN 0.25"-1". MORE IMPACTFUL, HOWEVER,
WILL THE BE THE GUSTY WINDS. WITH THE DEEPENING SURFACE LOW
POSITIONED TO OUR NORTHWEST, SYNOPTIC WIND GUSTS WILL BE IN THE
30-40 MPH RANGE. WORTH MONITORING, THOUGH, WILL BE THE POTENTIAL
FOR CONVECTIVE SHOWERS TO HELP TRANSFER MOMENTUM DOWNWARD FROM A
50 KT, 925-MB JET CORE. IF THIS WERE TO HAPPEN, WE COULD BE
DEALING WITH A FEW 40-50 MPH GUSTS, PARTICULARLY MONDAY NIGHT.
AFTER THE MONDAY SYSTEM GOES THROUGH ITS OCCLUSION AND PHASES
TOGETHER WITH ANOTHER TROUGH DIGGING OUT OF THE PACIFIC
NORTHWEST, THE MIDWEST WILL ONCE AGAIN BE FACING A POWERHOUSE
LATE-AUTUMN STORM SYSTEM. WHILE ALL SIGNS POINT TO A DEEPENING
UPPER- LEVEL LOW BOTTOMING-OUT SOMEWHERE OVER THE GREAT LAKES,
JUST HOW DEEP AND EXACTLY WHERE IT DEVELOPS REMAINS AN ENIGMA.
HONING-IN ON DETERMINISTIC GLOBAL GUIDANCE SUCH AS THE GFS AND
ECMWF HAS LARGELY BEEN USELESS, WITH THE STORM TRACK FRUSTRATINGLY
BOUNCING BACK-AND-FORTH SOMEWHERE BETWEEN INDY AND CLEVELAND.
THIS, OF COURSE, CAN DRAMATICALLY CHANGE OUR WIND AND SNOW
FORECAST. BUT, IF WE KEY-IN ON THE BLENDED (NBM) AND ENSEMBLE
(LREF) GUIDANCE, WE CAN TAKE A MORE PROBABILISTIC APPROACH WHICH
LEADS US TO A FEW EARLY CONCLUSIONS: (1) GUSTY WINDS IN THE 30-40
MPH REALM; (2) A LOW PROBABILITY (< 15% CHANCE) FOR A 2" SNOWFALL;
AND (3) A HIGH PROBABILITY (> 50%) CHANCE FOR SUB-FREEZING
OVERNIGHT TEMPERATURES SOMETIME BETWEEN WEDNESDAY NIGHT AND FRIDAY
NIGHT. AS ALWAYS, WE WILL NEED SOME MORE TIME TO MONITOR SNOW
TRENDS. EVEN TAKING AN ENSEMBLE APPROACH, THE MEAN OFTEN
CAMOUFLAGES THE VARIANCE.
MJA
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1043 PM CST SAT NOV 16 2024
LOW LEVEL MOISTURE AHEAD OF AN APPROACHING FRONTAL ZONE WILL
BRING DECREASING CEILINGS LATE TONIGHT INTO SUNDAY AFTERNOON, AS
WELL AS A CHANCE FOR SCATTERED SPRINKLES OR SHOWERS. NUMERICAL
AND STATISTICAL GUIDANCE HAS TRENDED TOWARD HIGHER CIGS, REMAINING
VFR INTO SUNDAY AFTERNOON, SO HAVE HELD OFF MVFR CIGS UNTIL AROUND
00Z. ALTHOUGH SCATTERED SPRINKLES ARE POSSIBLE, THERE IS LITTLE
CHANCE FOR ANY MVFR VSBY TO DEVELOP. WINDS SSE AROUND 10-15 KTS
OVERNIGHT, SHIFTING TO SSW AND DECREASING SLIGHTLY BY BY AROUND
14Z. WIND SPEEDS CONTINUE TO GRADUALLY DECREASE SUNDAY AFTERNOON
AND EVENING.
37
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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