366
FXUS63 KLOT 141807
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
107 PM CDT WED OCT 14 2026
KEY MESSAGES
- TODAY WILL START OUT DRAB WITH MOSTLY CLOUDY SKIES. A FEW
SHOWERS OR AREAS OF DRIZZLE CANNOT BE RULED OUT THROUGH THE
AFTERNOON.
- A FALL STORM SYSTEM WILL MOVE THROUGH THE AREA THURSDAY AND
FRIDAY BRINGING PERIODS OF RAIN SHOWERS AND GUSTY
NORTHWESTERLY WINDS (THE LATTER PRIMARILY ON FRIDAY).
- FROSTY AND LOCALLY FREEZING CONDITIONS ARE FAVORED AWAY FROM
LAKE MICHIGAN FRIDAY NIGHT INTO SATURDAY.
- AFTER THE BRIEF PERIOD OF CHILLY WEATHER, THERE WILL BE A
WARMING TREND THIS WEEKEND INTO EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 210 AM CDT WED OCT 14 2026
THOUGH TONIGHT:
EARLY MORNING GOES-19 WATER VAPOR IMAGERY DEPICTS A (NEARLY
CUT-OFF) UPPER-LEVEL TROUGH PROPAGATING ATOP THE FOUR CORNERS
REGION. SEVERAL CLUSTERS OF SHOWERS AND THUNDERSTORMS ARE
ONGOING AHEAD OF THE TROUGH ASSOCIATED WITH SEVERAL UPPER-
LEVEL VORTICITY MAXIMA PROPAGATING ATOP AN ELONGATED BAROCLINIC
ZONE DRAPED FROM THE SOUTHERN PLAINS THROUGH THE LOWER GREAT
LAKES. LOCALLY, HAVE BEEN MONITORING SCATTERED STORMS ACROSS THE
AREA THOUGH RELATIVELY MEAGER INSTABILITY IS MAINTAINING A
RELATIVELY GENERIC QUALITY INTENSITY IN SPITE OF AN OTHERWISE
FAVORABLE SHEAR PROFILE FOR ORGANIZED CONVECTION. MEANWHILE, A
SPRAWLING 1020MB+ SURFACE HIGH PRESSURE SYSTEM IS BUILDING INTO
THE NORTHERN PLAINS, AHEAD OF WHICH AN EXPANSIVE REGION OF LOW-
LEVEL STRATUS IS OOZING SOUTHWARD THROUGH THE UPPER MIDWEST.
AFTER DAYBREAK, THE AFOREMENTIONED SURFACE HIGH PRESSURE SYSTEM
WILL SHIFT EASTWARD TOWARD THE UPPER GREAT LAKES LEADING TO AN
INCREASE IN NORTHEASTERLY FLOW ACROSS NORTHERN ILLINOIS AND
NORTHWESTERN INDIANA. AS A RESULT, THE LOW-LEVEL BAROCLINIC ZONE
IN WHICH SHOWERS AND THUNDERSTORMS ARE ONGOING WILL SHIFT
SOUTHWARD WITH TIME. LOW-LEVEL ONSHORE FLOW WITHIN A MARGINALLY
UNSTABLE LAKE EFFECT REGIME BENEATH A STOUT LOW-LEVEL INVERSION
WILL REINFORCE LOW-LEVEL STRATUS THROUGH THE MORNING AND EARLY
AFTERNOON HOURS, LEADING TO A GRAY START TO THE DAY. CANNOT RULE
OUT A FEW INSTANCES OF SPRINKLES OR DRIZZLE NEAR LAKE MICHIGAN
OR NEAR US-24 (CLOSER TO THE LOW-LEVEL BAROCLINIC ZONE), SO WILL
MAINTAIN LOW-END POPS (10-20% CHANCES) GENERALLY EAST OF I-39
AND SOUTH OF I-80 THROUGH THE DAY. THE HIGH TEMPERATURE FORECAST
WILL HINGE ENTIRELY ON WHETHER OR NOT STRATUS IS ABLE TO CLEAR
BY EARLY THIS AFTERNOON, WITH HIGH RES GUIDANCE PROVIDING AN
AFFIRMATIVE "NO." AS SUCH GUIDANCE CAN SOMETIMES BE TOO
AGGRESSIVE WITH STRATUS, WILL TAKE THE MIDDLE GROUND AND ADVERTISE
HIGHS IN THE LOW TO MID 60S NORTH OF I-80 AND UPPER 60S TO
AROUND 70 SOUTH OF I-80 KEEPING IN MIND ACTUAL VALUES MAY VERIFY PLUS
OR MINUS A FEW DEGREES OF OUR FORECAST.
TONIGHT LOOKS QUIET. INCREASING UPPER-LEVEL CLOUD COVER AND
CONTINUED ONSHORE FLOW WILL HOLD OVERNIGHT LOWS GENERALLY IN THE
MID TO UPPER 50S, WARMEST NEAR LAKE MICHIGAN AND NEAR US-24.
THURSDAY INTO FRIDAY:
ENSEMBLE MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT THAT THE
SOUTHWESTERN US TROUGH WILL EJECT NORTHEASTWARD AND PHASE WITH
A NORTHERN-STREAM TROUGH SCREAMING SOUTHEASTWARD OUT OF CANADA.
AM NOTING INCREASING AGREEMENT IN THE EXACT TRACK AND EVOLUTION
OF THE RESULTING SURFACE LOW, EMERGING FROM NEAR DODGE CITY, KS
THURSDAY MORNING TO KANSAS CITY, MISSOURI BY EARLY AFTERNOON,
PASSING DIRECTLY OVER OUR AREA THURSDAY EVENING, AND THEN
CONTINUING TOWARD SOUTHERN ONTARIO OVERNIGHT INTO FRIDAY.
AS THE SURFACE LOW APPROACHES ON THURSDAY, GRADUALLY INCREASING
LOW-LEVEL ISENTROPIC ASCENT WITHIN THE NORTHWARD-MOVING
BAROCLINIC ZONE MAY SUPPORT AREAS OF DRIZZLE AND RAIN SHOWERS AS
EARLY AS DAYBREAK BEFORE A HIGHER COVERAGE OF SHOWERS SLIDES
OVERHEAD DURING THE AFTERNOON AND EVENING HOURS. SUPPOSE THERE
MAY BE A THUNDERSTORM OR TWO AS WELL, PARTICULARLY THURSDAY
EVENING AS A NARROW INSTABILITY AXIS ATTEMPTS TO LIFT NORTHWARD
AHEAD OF A SOUTHEASTWARD-MOVING COLD FRONT. THE SEVERE WEATHER
THREAT CONTINUES TO LOOK VERY LOW FOR OUR AREA BOTH FROM A
CONCEPTUAL MODEL FRAMEWORK AS WELL AS FROM EXPLICIT OUTPUT (OF
NEARLY ZERO PROBABILITIES) FROM ML-BASED GUIDANCE. WITH OUR AREA
SMACK-DAB IN THE MIDDLE OF THE BAROCLINIC ZONE, AM ANTICIPATING
QUITE A GRADIENT IN HIGH TEMPERATURES ON THURSDAY. WILL
UNDERCUT NBM GUIDANCE AND FEATURE HIGHS IN THE UPPER 50S NEAR
AND NORTH OF I-88 AND LOWER 60S SOUTH OF I-80. TAKEN ALTOGETHER,
THURSDAY LOOKS FAIRLY DRAB.
THERE REMAINS AGREEMENT THAT AN UNUSUALLY STRONG SURFACE HIGH
PRESSURE SYSTEM WILL QUICKLY BUILD INTO THE CENTRAL UNITED
STATES IN THE WAKE OF THE DEPARTING SURFACE LOW LEADING TO AN
IMPRESSIVE 40 TO 45 MB PRESSURE GRADIENT DIRECTLY OVER THE GREAT
LAKES ON FRIDAY. A SOMEWHAT BIFURCATED PRESSURE RISE COUPLET (A
CONSEQUENCE OF THE UPPER-LEVEL TROUGHS PHASING DIRECTLY
OVERHEAD) SUGGEST A ONE-TWO PUNCH TO WINDS ON THE BACKSIDE OF
THE SYSTEM WITH A PERIOD OF GUSTY NORTHWESTERLY WINDS OF 30 TO
35 MPH FRIDAY MORNING FOLLOWED BY A STRONGER PERIOD OF GUSTS OF
35 TO 40 MPH DURING THE AFTERNOON AND EVENING HOURS. GUSTS MAY
BE HIGHER (LOCALLY 45 MPH) ALONG THE LAKE AND PORTER INDIANA
SHORELINES OF LAKE MICHIGAN WHERE LAKE INSTABILITY WILL SUPPORT
DEEPER MIXING PROFILES.
TUMBLING COLUMN TEMPERATURES BY WAY OF EFFICIENT COLD-AIR
ADVECTION WILL SUPPORT A FLARE IN DIURNAL INSTABILITY
LEADING TO AN EXPANSIVE STRATUS DECK. WHILE ENSEMBLE MEAN
TEMPERATURES SUPPORT HIGHS IN THE LOW TO MID 50S, AM NOTING
QUITE A FEW INDIVIDUAL MEMBERS AND DETERMINISTIC COUNTERPARTS
SHOWING EXPLICIT UPPER 40 DEGREE HIGHS ACROSS NORTHWESTERN
ILLINOIS. WILL (ONCE AGAIN) UNDERCUT NBM GUIDANCE TO FEATURE
HIGHS IN THE LOWER 50S AS A HAPPY MEDIUM.
AS THE CORE OF THE NORTHERN-STREAM TROUGH SLIDES OVERHEAD (PEAK
DIURNAL INSTABILITY), CAN ENVISION ISOLATED TO SCATTERED
SHOWERS ACCOMPANIED BY LOCALLY GUSTIER WINDS MOVING THROUGH THE
AREA DURING THE AFTERNOON HOURS. COVERAGE OF GUSTY SHOWERS
SHOULD BE MAXIMIZED IN NORTHWESTERN INDIANA BY SUNSET WHERE
850MB TO MARINE AIRMASS TEMPERATURE DIFFERENTIALS OF 15 TO 20C
WITHIN THE CYCLONIC SHEAR SIDE OF THE UPPER-LEVEL TROUGH WILL
PUSH LAKE-INDUCED INSTABILITY TOWARD 500 J/KG. (IT'LL BE PRETTY
RAW OUT THERE ALONG NORTHWESTERN INDIANA COMMUNITIES).
FRIDAY NIGHT ONWARD:
LAKE EFFECT RAIN SHOWERS SHOULD END OVERNIGHT AS INVERSION
HEIGHTS CRASH ON THE BACKSIDE OF THE DEPARTING UPPER-LEVEL
TROUGH AND THE SURFACE HIGH PRESSURE SYSTEM SLIDES INTO THE
MIDDLE MISSISSIPPI RIVER VALLEY. WITH WEAKENING WINDS AND
CLEARING SKIES, OVERNIGHT LOWS WILL BE POISED TO BE THE COLDEST
OF THE AUTUMN SEASON SO FAR WITH WIDESPREAD READINGS IN THE LOW
TO MID 30S. THE EXCEPTION WILL BE NEAR LAKE MICHIGAN AND ALONG
THE I-65 CORRIDOR WHERE LOWS WILL BOTTOM OUT IN THE LOWER 40S
THANKS TO TO THE CONTINUED INFLUENCE OF LAKE MICHIGAN AND
LINGERING LAKE EFFECT STRATUS. ASSUMING NO MAJOR CHANGES TO THE
FORECAST, WILL HAVE TO CONSIDER FREEZE WATCHES FOR PORTIONS OF
THE AREA BEFORE TOO LONG.
THEREAFTER, ENSEMBLE GUIDANCE ADVERTISES THE SURFACE HIGH
STALLING OVER THE ATLANTIC SEABOARD AND THE NORTHWARD RETREAT
OF THE DOMINANT UPPER-LEVEL JET INTO CANADA SUPPORTING GRADUALLY
RISING TEMPERATURES AND GENERALLY DRY WEATHER INTO NEXT WEEK.
ENSEMBLE METEOGRAMS OF QPF FROM ALL ENSEMBLE SUITES DEPICT A
TRANSITION TOWARD A SOMEWHAT SHOWERY PATTERN WITH SEASONABLE
TEMPERATURES DURING THE THE THE LAST 5 TO 10 DAYS OF THE MONTH.
BORCHARDT
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 107 PM CDT WED OCT 14 2026
KEY MESSAGES:
- MVFR CEILINGS WILL CONTINUE THIS AFTERNOON.
- RAIN IS EXPECTED TOMORROW WITH ASSOCIATED LOWERED CEILINGS AND
VISIBILITIES.
MVFR CEILINGS ARE BEING OBSERVED AT ALL OF OUR TAF SITES AT
PRESS TIME EARLY THIS AFTERNOON. SOME LIFTING AND/OR SCATTERING
OF THIS MVFR STRATOCUMULUS WITH TIME SHOULD ALLOW FOR VFR
CONDITIONS TO RETURN TO AT LEAST A FEW OF OUR TAF SITES BY THIS
EVENING, BUT CONFIDENCE IN PRECISE CEILING TRENDS THROUGH
TONIGHT IS NOT VERY HIGH.
REGARDLESS, CEILINGS WILL DETERIORATE TOMORROW AS A SLUG OF RAIN
ASSOCIATED WITH AN INCOMING LOW PRESSURE SYSTEM PUSHES INTO THE
AREA FROM THE SOUTHWEST. A PERIOD OF IFR CEILINGS IS LIKELY
TOMORROW AFTERNOON, AND THERE IS A SIGNAL IN FORECAST GUIDANCE
FOR LIFR CEILINGS TO BE OBSERVED AS WELL. MVFR OR LOWER
VISIBILITIES ARE ALSO LIKELY TO BE OBSERVED AT TIMES TOMORROW
DURING THE STEADIER RAINFALL. COULDN'T RULE OUT SOME ISOLATED
LIGHTNING STRIKES OCCURRING TOMORROW AFTERNOON, PARTICULARLY
NEAR GYY AND MDW, THOUGH THE BETTER THUNDERSTORM POTENTIAL
SHOULD REMAIN SOUTH OF THE TERMINALS.
WINDS THROUGH THE TAF PERIOD ARE EXPECTED TO RETAIN AN EASTERLY
COMPONENT WITH MAGNITUDES AVERAGING OUT NEAR OR JUST UNDER 10
KTS.
OGOREK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 1 PM CDT
THURSDAY FOR WINTHROP HARBOR TO WILMETTE HARBOR IL.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM CDT
THURSDAY FOR WILMETTE HARBOR TO NORTHERLY IS. IL.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM CDT
THURSDAY FOR NORTHERLY IS. IL TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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