860
FXUS63 KLOT 181802
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1202 PM CST MON NOV 18 2024
KEY MESSAGES
- PERIODS OF RAIN LATER TODAY THROUGH TUESDAY MORNING, ALONG
WITH A SLIGHT CHANCE OF THUNDERSTORMS TONIGHT. SOME SHOWERS
AND STORMS TONIGHT MAY PRODUCE LOCALLY GUSTY WINDS.
- STRONG AMBIENT SOUTHERLY WINDS TONIGHT INTO TUESDAY MORNING,
WITH GUSTS OF 30-40 MPH POSSIBLE.
- THE FIRST SNOWFLAKES OF THE SEASON APPEAR LIKELY WEDNESDAY
NIGHT INTO THURSDAY MORNING, WITH A CHANCE FOR THE FIRST
MEASURABLE SNOW (I.E. AT LEAST 0.1") FOR SOME OF THE AREA.
- A COLDER AIR MASS WITH BELOW NORMAL TEMPERATURES WILL SETTLE
ACROSS THE AREA THURSDAY THROUGH THE UPCOMING WEEKEND.
DISCUSSION
ISSUED AT 340 AM CST MON NOV 18 2024
THROUGH TUESDAY:
WIDESPREAD DENSE FOG DEVELOPED LATE LAST EVENING ACROSS FAR
NORTHERN IL, MAINLY NEAR AND NORTH OF THE I-88 CORRIDOR. AN
EXPANSIVE STRATUS DECK ACROSS THE REMAINDER OF THE AREA HAS BEEN
SPREADING SLOWLY NORTH OVER THE PAST FEW HOURS, ALLOWING
VISIBILITY TO SLOWLY IMPROVE CLOSER TO I-88. VISIBILITY SHOULD
ALSO GRADUALLY IMPROVE FARTHER NORTH AS THE CLOUD DECK
CONTINUES TO LIFT TOWARD THE IL/WI BORDER, BUT FOR NOW A DENSE
FOG ADVISORY REMAINS IN EFFECT UNTIL 7 AM.
UPSTREAM TO OUR SOUTHWEST, A VIGOROUS MID-LEVEL SHORT WAVE WAS
EVIDENT IN VAPOR IMAGERY ACROSS NM/TX THIS MORNING, WITH A
CORRESPONDING 983 HPA SURFACE LOW CENTERED NEAR LUBBOCK TX. THE
MID-LEVEL WAVE IS PROGGED TO TAKE ON A NEGATIVE-TILT, AND LIFT
STEADILY NORTHEAST INTO THE UPPER MISSISSIPPI VALLEY THROUGH
TUESDAY MORNING. IN THE PROCESS, THE SYSTEM IS EXPECTED TO
BECOME VERTICALLY STACKED ABOVE IT'S OCCLUDING SURFACE LOW WHICH
IS EXPECTED TO BE OVER CENTRAL MN BY TUESDAY MORNING. THIS
ROBUST WAVE WILL INDUCE STRENGTHENING SOUTH-SOUTHEAST LOW-LEVEL
WINDS ACROSS THE AREA TONIGHT INTO TUESDAY MORNING, WHICH MAY
PRODUCE GUSTS OF 30-40 MPH AT TIMES. THESE STRENGTHENING WINDS,
MORE SOUTH-SOUTHWESTERLY ALOFT, WILL ALSO RESULT IN STRONG
WARM/MOIST ADVECTION INTO THE REGION BEGINNING TODAY, SPREADING
SHOWERS INTO THE FORECAST AREA FROM SOUTH TO NORTH LATER THIS
MORNING AND AFTERNOON. THERE MAY BE A LULL IN THE SHOWER
ACTIVITY FOR A TIME EARLY THIS EVENING, BEFORE MORE WIDESPREAD
RAIN AND SOME EMBEDDED THUNDERSTORMS ARRIVE AHEAD OF THE PRIMARY
MID-LEVEL WAVE AND OCCLUDING FRONTAL SYSTEM LATE THIS EVENING
AND OVERNIGHT. WITH THE STRONG WINDS ALOFT, SOME OF THESE
SHOWERS AND STORMS TONIGHT MAY PRODUCE LOCALLY GUSTY WINDS IN
EXCESS OF 30 MPH.
THE SHORT WAVE WILL LIFT NORTH OF THE AREA TUESDAY MORNING,
WITH DRIER MID-LEVEL AIR SPREADING ACROSS THE CWA DURING THE
DAY. SHOWERS SHOULD DECREASE IN COVERAGE FROM SOUTHWEST TO
NORTHEAST TUESDAY MORNING, WITH MOST OF THE AREA REMAINING DRY
FOR THE REMAINDER OF THE DAY, THOUGH A FEW ADDITIONAL STRAY
SPRINKLES CAN'T BE COMPLETELY RULED OUT. GUSTY SOUTHWEST WINDS
SHOULD EASE A BIT BY AFTERNOON AS THE SURFACE PRESSURE GRADIENT
RELAXES. TEMPERATURES WILL BE QUITE MILD FOR MID-LATE NOVEMBER.
HIGHS TODAY SHOULD REACH THE MID-50S NORTH AND THE LOWER 60S
SOUTH, AND LOWER 60S ARE EXPECTED FOR MOST OF THE AREA ON
TUESDAY. OVERNIGHT LOWS TONIGHT WILL REMAIN IN THE MID AND UPPER
50S, A GOOD 10 DEGREES OR SO ABOVE OUR AVERAGE HIGHS.
RATZER
TUESDAY NIGHT THROUGH SUNDAY:
THE MID-LEVEL WAVE LIFTING NNE ACROSS THE CENTRAL GREAT PLAINS
TODAY WILL PHASE WITH A SERIES OF PACIFIC-BASED WAVES THROUGH
MID-WEEK, ULTIMATELY CONGEALING INTO A BROAD UPPER-LEVEL LOW
THAT IS EXPECTED TO DRIFT ESE ACROSS THE GREAT LAKES REGION MID
TO LATE WEEK. THE LOW WILL INGEST MUCH COLDER AIR FROM AN ARCTIC
AIR RESERVOIR OVER WESTERN CANADA AND THE PACIFIC NORTHWEST
WHILE ALSO DYNAMICALLY COOLING. THIS WILL SET THE STAGE FOR THE
COLDEST AIR OF THE SEASON TO FILTER ACROSS THE AREA WHILE ALSO
SUPPORTING THE POTENTIAL FOR THE FIRST SNOWFLAKES OF THE SEASON
WEDNESDAY NIGHT INTO THURSDAY.
AFTER AN UNSEASONABLY WARM DAY ON TUESDAY, A COLD FRONT WILL
USHER IN STRONG CAA ACROSS THE AREA LATE TUESDAY NIGHT THROUGH
THE DAY WEDNESDAY. THIS WILL OCCUR AS ONE OF THE PHASING WAVES
EXITS THE CENTRAL ROCKIES TOWARD THE WESTERN GREAT LAKES BY
WEDNESDAY MORNING. THOUGH DECENT DRY AIR ADVECTION IS EXPECTED
TO OCCUR IN CONCERT WITH THE CAA, THE WAVE MAY ARRIVE EARLY
ENOUGH TO BLOSSOM AN AREA OF RAIN ACROSS INDIANA AND LOWER
MICHIGAN WEDNESDAY MORNING. A SERIES OF MID- LEVEL PV LOBES
ROTATING CYCLONICALLY ACROSS THE UPPER MISSISSIPPI RIVER VALLEY
ARE THEN EXPECTED TO PRODUCE SCATTERED SHOWERS LATE WEDNESDAY
AFTERNOON THROUGH THURSDAY NIGHT AND POSSIBLY WELL INTO FRIDAY.
THERMAL PROFILES WILL QUICKLY BECOME FAVORABLE FOR A TRANSITION
FROM RAIN TO SNOW WITH THESE SHOWERS BY WEDNESDAY EVENING, WITH
THE EXPECTATION THAT PRECIP WILL BE ALL SNOW (EXCEPT NEAR THE
IMMEDIATE NW IN SHORE) LATE WEDNESDAY EVENING INTO THURSDAY
MORNING. WHILE IT IS BECOMING MORE LIKELY THAT WE WILL SEE THE
FIRST SNOWFLAKES OF THE SEASON WEDNESDAY NIGHT, MODEST FORCING
WITH THE LOBES ROTATING THROUGH THE BROADER LOW COMBINED WITH
DECENT DEEPER MOISTURE SUGGESTS WE COULD ALSO SEE THE FIRST
MEASURABLE SNOW (A FEW TENTHS OF AN INCH) FOR MANY LOCATIONS.
AS AN ADDED CLIMATE NOTE, CHICAGO HAS YET TO EXPERIENCE A
TEMPERATURE OF 32F OR LOWER THIS SEASON. THIS IS NOW THE 5TH
LATEST DATE FOR THE FIRST 32F OR LOWER IN THE COOL SEASON, AND
THE LATEST SINCE 1931. THE RECORD LATEST OCCURRED ON 11/24
(1931). BASED ON THE CURRENT FORECAST, CHICAGO WILL HAVE
MULTIPLE CHANCES TO REACH 32F OR LOWER LATE THIS WEEK THROUGH
THE WEEKEND.
SPREAD IN GUIDANCE CONTINUES TO GROW BEYOND THURSDAY MORNING
OWING TO THE INTRICATE INTERACTIONS OF THE SEVERAL WAVES
ROTATING THROUGH THE BROADER LOW ACROSS THE REGION. ENSEMBLE
GUIDANCE DOES KEEP A VAST MAJORITY OF THE PRIMARY FORCING AND
DEEPER MOISTURE ACROSS INDIANA INTO PENNSYLVANIA THURSDAY
AFTERNOON INTO FRIDAY. THIS FORECAST FOLLOWS SUITE WITH ONLY
SOME RESIDUAL RAIN SHOWERS (MIXED WITH SNOW AT NIGHT) OUTSIDE OF
THE NW WIND LAKE EFFECT BELTS, WHERE PERIODS OF LAKE EFFECT
RAIN SHOWERS ARE FAVORED POTENTIALLY INTO SATURDAY.
KLUBER
AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 1202 PM CST MON NOV 18 2024
KEY AVIATION MESSAGES:
- SHRA WITH PERIODS OF IFR CEILINGS THIS AFTERNOON AND AGAIN
LATE THIS EVENING THROUGH THE OVERNIGHT HOURS.
- 10-20% CHANCE OF TS WITH THE SECOND ROUND OF SHRA TONIGHT.
- SE WINDS GUSTING TO 30 KNOTS VEERING SSW AROUND SUNRISE
TUESDAY. A COUPLE HOUR PERIOD OF STRONGER SOUTH-SOUTHWEST
WINDS (GUST 35+ KT) POSSIBLE AROUND SUNRISE TUESDAY MORNING.
CONDITIONS CONTINUE TO QUICKLY DETERIORATE ACROSS THE NORTHERN
IL AND NORTHWESTERN IN TERMINALS THIS MIDDAY HOUR. THE
EXPECTATION THROUGH MID TO LATE THIS AFTERNOON IS FOR IFR (SOME
PATCHY LIFR) CIGS AND VSBYS TO PERSIST AHEAD OF A SURFACE WARM
FRONT. PERIODS OF RAIN CAN ALSO BE EXPECTED AS WARM FRONTAL BAND
OF RAIN CONTINUES TRACKING NORTHWARD ACROSS THE AREA. IT APPEARS
THE STEADIER RAIN WILL BECOME MORE SHOWERY, OR EVEN STOP FOR A
FEW HOUR PERIOD, AROUND SUNSET LATE THIS AFTERNOON (22-23Z) AS
THIS INITIAL FRONTAL DRIVEN BAND OF RAIN TRACKS NORTH OUT OF
THE AREA. WHILE VSBYS WILL IMPROVE WITH THE END OF THE RAIN,
SOME LOWER CIGS COULD LINGER FOR A COUPLE HOURS INTO EARLY THIS
EVENING BEFORE A PERIOD OF IMPROVING CIGS (VFR) IS LIKELY.
ANY IMPROVEMENT THIS EVENING WILL BE SHORT LIVED, HOWEVER, AS
ANOTHER BAND OF SHOWERS (POSSIBLY EVEN A FEW THUNDERSTORMS) IS
SLATED TO SLIDE EASTWARD INTO THE AREA IN ADVANCE OF AN
APPROACHING COLD FRONT. THE BEST TIMING FOR THIS LINE OF SHOWERS
WILL BE IN THE 05 TO 08Z TIMEFRAME AT THE CHICAGO AREA
TERMINALS, AND SLIGHTLY EARLIER AT KRFD. THE CURRENT TEMPO IN
THE TAFS HIGHLIGHTS THIS TIMING. ABOUT A 5-15% CHANCE FOR A
FEW RUMBLES OF THUNDER ALSO EXISTS WITH THIS LINE OF SHOWERS
TONIGHT, BUT WITH THE CHANCES BEING TOO LOW, THERE CONTINUES TO
BE NO FORMAL MENTION IN THE TAF.
WINDS WILL BECOME INCREASINGLY GUSTY (25-30 KT) FROM THE
SOUTHEAST THIS EVENING AND TONIGHT AS A STRONG SURFACE LOW
TRACKS NORTHEASTWARD ACROSS THE MID-MISSOURI VALLEY. WINDS WILL
THEN SHIFT SOUTH-SOUTHWESTERLY AROUND (OR A BIT BEFORE) DAYBREAK
TUESDAY MORNING AS A SURFACE COLD FRONT SWEEPS EASTWARD ACROSS
THE AREA. A PERIOD OF STRONG WIND GUSTS (35+KT) IS POSSIBLE
(40-50% CHANCE) WITH THE PASSAGE OF THIS FRONT. THESE STRONG
GUSTY WINDS WILL GRADUALLY EASE THROUGH THE AFTERNOON AS THEY
TURN WEST-SOUTHWESTERLY.
KJB
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM CST
TUESDAY FOR THE IL NEARSHORE WATERS.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 3 PM CST
TUESDAY FOR THE IN NEARSHORE WATERS.
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