850
FXUS63 KLOT 020506
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1106 PM CST THU DEC 1 2022
SHORT TERM
ISSUED AT 326 PM CST THU DEC 1 2022
THROUGH SATURDAY...
KEY FORECAST MESSAGES THROUGH SATURDAY:
*GUSTY WINDS FRIDAY THROUGH SATURDAY WITH GUSTS OF 40 TO 45 MPH
EXPECTED.
*CHANCE FOR LIGHT RAIN SHOWERS AND/OR DRIZZLE LATE FRIDAY AFTERNOON
AND EVENING ALONG A COLD FRONT.
*RAPIDLY COOLING TEMPERATURES FRIDAY NIGHT BEHIND THE FRONT.
THE SURFACE HIGH THAT IS RESPONSIBLE FOR THE SUNNY SKIES TODAY
CONTINUES TO MOVE EASTWARD INTO THE NORTHEAST THIS AFTERNOON AS A
DEVELOPING SURFACE LOW MOVES INTO THE NORTHERN PLAINS AHEAD OF AN
UPPER-LEVEL TROUGH THAT IS MOVING THROUGH THE PACIFIC NORTHWEST. THE
SURFACE LOW IS EXPECTED TO CONTINUE TO DEEPEN AS IT MOVES INTO THE
NORTHERN GREAT LAKES AND SOUTHERN CANADA THROUGH THE DAY ON FRIDAY
WHICH WILL CREATE A TIGHTENING PRESSURE GRADIENT ACROSS NORTHEASTERN
ILLINOIS AND NORTHWEST INDIANA AHEAD OF A COLD FRONT THAT WILL SWING
THROUGH THE AREA FRIDAY EVENING. THIS WILL ALLOW GUSTY SOUTHERLY
WINDS TO DEVELOP ACROSS THE AREA LATE TONIGHT AND LINGER INTO THE
DAY ON SATURDAY WITH WIND GUSTS OF 30 TO 35 MPH ON FRIDAY BECOMING
WESTERLY 40 TO 45 MPH FRIDAY NIGHT INTO SATURDAY MORNING BEHIND THE
COLD FRONT. THERE CONTINUES TO BE SOME UNCERTAINTY IN EXACTLY HOW
STRONG THE WINDS WILL BECOME ESPECIALLY IN THE WARM ADVECTION WING
FRIDAY AFTERNOON, BUT IF THE ATMOSPHERE IS ABLE TO MIX AS FORECAST
SOUNDINGS SUGGEST HIGHER GUSTS COULD CERTAINLY BE REALIZED DURING
THE AFTERNOON AND EVENING HOURS. THE STRONGEST WINDS ARE EXPECTED TO
ARRIVE BEHIND THE COLD FRONT AS STRONG COLD ADVECTION TAKES OVER AND
ALLOWS THE ATMOSPHERE TO TAP INTO A STRONG LOW-LEVEL JET AND BRINGS
40 TO 45 MPH GUSTS TO THE SURFACE. WHILE THESE WINDS ARE CLOSE TO
WIND ADVISORY CRITERIA I DECIDED TO HOLD OFF ON A FORMAL ISSUANCE
FOR NOW GIVEN THE LINGERING UNCERTAINTY AND TIME RANGE OF THE
STRONGEST WINDS, BUT ONE MAY BE NEEDED WITH THE OVERNIGHT FORECAST
UPDATE.
IN ADDITION TO THE WINDS, THE COLD FRONT WILL ALSO BRING WITH IT THE
CHANCE FOR LIGHT RAIN SHOWERS AND/OR DRIZZLE LATE FRIDAY AFTERNOON
INTO THE EARLY PART OF SATURDAY MORNING. FORECAST SOUNDINGS CONTINUE
TO SHOW THAT WHILE THE LOW-LEVELS ARE RATHER SATURATED THE MID-
LEVELS ARE EXPECTED TO REMAIN DRY. THIS DRY AIR SHOULD LIMIT THE
DEVELOPMENT OF MORE ROBUST PRECIPITATION AND KEEP ANY SHOWERS LIGHT
AND CONFINED MOSTLY TO THE COLD FRONT. HOWEVER, SOME POCKETS OF
DRIZZLE DO LOOK TO BE POSSIBLE LATE FRIDAY AFTERNOON AS SURFACE
MOISTURE SURGES INTO THE REGION. PRECIPITATION CHANCES WILL COME TO
AN END AS THE FRONT PASSES WITH MOST AREAS EXPECTED TO BE RAIN-FREE
BY SATURDAY MORNING.
LASTLY, TEMPERATURES WILL BE A ROLLER COASTER TO CLOSE OUT THE WEEK
AND START THE WEEKEND. THE WARM ADVECTION AHEAD OF THE FRONT WILL
ALLOW TEMPERATURES TO WARM INTO UPPER 40S AND LOWER 50S FRIDAY
AFTERNOON AND EVENING, BUT ONCE THE FRONT PASSES THE STRONG COLD
ADVECTION BEHIND IT WILL CAUSE TEMPERATURES TO PLUMMET HEADING INTO
SATURDAY MORNING. LOWS ON SATURDAY MORNING ARE EXPECTED TO START OFF
IN THE UPPER TEENS AND LOWER 20S WITH WIND CHILLS IN THE SINGLE
DIGITS FOR MOST AREAS. HIGHS ON SATURDAY WILL ALSO BE COLD WITH
TEMPERATURES STRUGGLING TO REACH FREEZING. DESPITE THE COLD
TEMPERATURES SKIES WILL CLEAR OUT THROUGH THE DAY ON SATURDAY AS HIGH
PRESSURE BUILDS BACK INTO THE AREA WITH WINDS GRADUALLY EASING
THROUGH THE DAY AS WELL.
YACK
LONG TERM
ISSUED AT 252 PM CST THU DEC 1 2022
SATURDAY NIGHT THROUGH THURSDAY...
EXPANSIVE HIGH PRESSURE DRIFTING EASTWARD ALONG THE OHIO RIVER
VALLEY WILL MAINTAIN DRY CONDITIONS THROUGH SUNDAY NIGHT AS SOME
UPPER-LEVEL CIRRUS FILTER OVER THE AREA. WITH A RATHER DRY AIRMASS
IN PLACE, A WEAKENING LOW-LEVEL TROUGH PASSING NORTH OF THE AREA
WILL BRING ONLY BLUSTERY CONDITIONS WITH WSW GUSTS OVER 25 MPH ON
SUNDAY AFTERNOON.
BROAD SUB-TROPICAL RIDGING OVER THE GULF OF MEXICO AND A LONG-
WAVE TROUGH OVER SOUTHERN CANADA WILL ENHANCE MID-LEVEL WESTERLIES
EARLY NEXT WEEK AS SUBSTANTIAL BAROCLINICITY (40C N/S RANGE IN
THE CENTRAL CONUS) DEVELOPS. PRECIP POTENTIAL IN THE FORECAST AREA
WILL HINGE ON THE EXACT TIMING/STRENGTH OF ANY MID-LEVEL WAVES
PROPOGATING THROUGH THE STRONG MID-LEVEL FLOW, WITH
ENSEMBLE/DETERMINISTIC GUIDANCE VARIED ON THE TIMING OF ONE SUCH
EMBEDDED WAVE SOMETIME LATE MONDAY INTO EARLY TUESDAY. LOW-LEVEL
MOISTURE WILL REMAIN SUPPRESSED TO THE GULF COAST THROUGH SUNDAY,
SO AMPLE MOISTURE RETURN THIS FAR NORTH WILL NOT OCCUR UNTIL AT
LEAST LATE MONDAY OR EVEN TOWARD TUESDAY MORNING. FOR THAT REASON,
ANY TROUGH PASSAGE MONDAY INTO MONDAY NIGHT WILL NEED TO TAP INTO
LIMITED PACIFIC-SOURCED MID-LEVEL MOISTURE. PRIMARY PRECIP TYPE
WITH ANYTHING MONDAY AFTERNOON WOULD BE LIGHT RAIN/SHOWERS, THOUGH
WITH THE NOTED DEEP DRY AIRMASS, SNOW ALOFT WILL BE SUSCEPTIBLE
TO COMPLETELY SUBLIMATING BEFORE REACHING THE MELTING LAYER.
THE OVERALL COLUMN WILL GRADUALLY COOL INTO TUESDAY, WITH LOW
WET- BULB ZERO HEIGHTS FAVORING PRIMARILY SNOW FOR ANY PRECIP. BUT
WITH A VAST MAJORITY OF MODEL MEMBERS ALREADY ADVERTISING THE
PASSAGE OF THE TROUGH BY THIS POINT, THE CURRENT FORECAST
INDICATES ONLY A LOW CHANCE OF LIGHT SNOW.
THE SUB-TROPICAL RIDGE WILL REMAIN ENTRENCHED OVER THE GULF OF
MEXICO THROUGH THE REST OF THE WEEK, MAINTAINING STRONG MID-LEVEL
WESTERLIES THAT FOSTER AN ACTIVE STORM TRACK SOUTH OF THE CWA.
WITH OUR AIRMASSES ORIGINATING MORE FROM WESTERN CANADA THAN THE
PACIFIC NORTHWEST DURING THIS TIME, TEMPS WILL LIKELY REMAIN
SEASONABLE.
KLUBER
AVIATION
FOR THE 06Z TAFS...
THE MAIN AVIATION WEATHER CONCERNS INCLUDE:
* CONTINUED MARGINAL LLWS, MAINLY INVOF RFD TONIGHT
* WINDS BECOMING INCREASINGLY GUSTY THROUGH FRIDAY, WITH CROSSWIND
CHALLENGES FOR E-W RUNWAY OPERATIONS, ESPECIALLY LATER IN THE
AFTERNOON
* DEVELOPING MVFR CIGS FRIDAY AFTERNOON AND EVENING
* BRIEF POTENTIAL FOR SHOWERS AND/OR DRIZZLE AHEAD OF AND
IMMEDIATELY BEHIND AN ARCTIC COLD FRONT
* VERY STRONG AND GUSTY WNW WINDS FRIDAY NIGHT
SURFACE WINDS WILL REMAIN INTERMITTENTLY GUSTY OVERNIGHT, WITH A
PERIOD OF LLWS CONTINUING MAINLY AT RFD UNDER THE CORE OF THE
LOW-LEVEL JET. WIND SPEEDS AND GUSTS WILL CLIMB THROUGH THE DAY ON
FRIDAY, WITH ROUTINE GUSTS TOWARDS 35 KTS BY THE MID TO LATE
AFTERNOON. WINDS WILL FAVOR A 190-200 DIRECTION DURING THIS
PERIOD, WHICH WILL RESULT IN SOME CROSSWIND CHALLENGES ON E-W
RUNWAYS.
DEEPER MOISTURE IS EXPECTED TO ARRIVE THROUGH FRIDAY EVENING, AND
THIS MAY BE SUFFICIENT TO SQUEEZE OUT A PERIOD OF SHRA AND/OR DZ
AS MVFR CIGS OVERSPREAD THE REGION. PROB30S HAVE BEEN MAINTAINED
FOR THIS POTENTIAL. A POWERFUL COLD FRONT WILL ARRIVE AROUND 06Z
AT THE CHICAGO-AREA SITES WITH A WNW WIND SHIFT AND SHARPLY-
FALLING TEMPERATURES. WINDS LOOK TO GUST TOWARDS 40 KTS IN THE
WAKE OF THE FRONT BEFORE EASING SOMEWHAT BY EARLY SATURDAY
MORNING. AT THIS TIME, ALL PRECIPITATION IS EXPECTED TO END BEFORE
SURFACE TEMPERATURES FALL BELOW FREEZING.
CARLAW
MARINE
ISSUED AT 326 PM CST THU DEC 1 2022
ANOTHER QUICK-MOVING, DEEPENING LOW PRESSURE SYSTEM WILL CRUISE
EAST ACROSS THE INTERNATIONAL BORDER FRIDAY INTO EARLY SATURDAY.
THIS IS A VERY FAVORABLE SETUP FOR GALES, INCLUDING SOME HIGHER
END GALE GUSTS (40 TO MAYBE 45 KT) IMMEDIATELY BEHIND THE COLD
FRONT. THAT COLD FRONTAL TIMING FOR THE ILLINOIS AND INDIANA
NEARSHORE WATERS IS NEAR OR SHORTLY AFTER MIDNIGHT FRIDAY NIGHT.
SO THE PEAK WINDS WILL BE OVERNIGHT FRIDAY NIGHT INTO EARLY
SATURDAY MORNING. AHEAD OF THE FRONT ON FRIDAY, SOUTHERLY WIND
GUSTS WILL AT THE LEAST APPROACH GALES AND MAY FREQUENTLY GUST TO
35 KT DEPENDING ON MAGNITUDE OF MIXING. AS FOR BEHIND THE PEAK
GALES ON SATURDAY, WIND SPEEDS ON THE AFTERNOON LOOK TO COME DOWN
QUICKLY WITH RESIDUAL WAVE ACTION LIMITED DUE TO THE WESTERLY
COMPONENT OF THE WINDS. GIVEN THE CONTINUED CONFIDENCE IN GALE
FORCE GUSTS THE GALE WATCH HAS BEEN UPDATED TO A GALE WARNING
THROUGH SATURDAY MORNING.
MTF/YACK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...IL NEARSHORE WATERS UNTIL 3 PM FRIDAY.
GALE WARNING...LMZ740-LMZ741-LMZ742...3 PM FRIDAY TO NOON
SATURDAY.
SMALL CRAFT ADVISORY...IN NEARSHORE WATERS UNTIL 9 AM FRIDAY.
GALE WARNING...LMZ743-LMZ744-LMZ745...9 AM FRIDAY TO NOON
SATURDAY.
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