657
FXUS63 KLOT 062347
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
547 PM CST THU NOV 6 2025
KEY MESSAGES
- A PERIOD OF SHOWERS, POSSIBLY WITH A FEW ISOLATED
THUNDERSTORMS, EXPECTED TONIGHT INTO EARLY FRIDAY MORNING.
- TEMPERATURES WILL TREND COOLER ON SATURDAY AS RAIN ARRIVES LATER
IN THE DAY, FOLLOWED BY A SHARP COOL-DOWN SATURDAY NIGHT INTO
SUNDAY PROBABLY ACCOMPANIED BY THE FIRST SNOWFLAKES OF THE FALL.
- LAKE EFFECT/LAKE ENHANCED SNOW AND SOME ACCUMULATIONS ARE
POSSIBLE/PROBABLE SUNDAY THROUGH MONDAY EVENING, BUT
SIGNIFICANT UNCERTAINTY REGARDING EVOLUTION AND BAND PLACEMENT
CONTINUES.
DISCUSSION
ISSUED AT 247 PM CST THU NOV 6 2025
THROUGH FRIDAY NIGHT:
AN AREA OF SHOWERS (AND POSSIBLY A FEW NON-SEVERE THUNDERSTORMS)
WILL DEVELOP ACROSS EASTERN IA INTO WESTERN IL THIS EVENING AS
WARM ADVECTION INTENSIFIES IN ADVANCE OF AN APPROACHING COLD FRONT.
WHILE THE PARENT SURFACE LOW WILL TRACK WELL NORTH OF OR AREA
ACROSS THE UP OF MICHIGAN AND LAKE SUPERIOR, LARGE SCALE FORCING
LOOKS SIGNIFICANT DOWN THIS WAY AS 120 TO 150 M/12 HOUR MID-LEVEL
HEIGHT FALLS AND SIGNIFICANT DCVA OVERSPREAD THE AREA OVERNIGHT.
ACCORDINGLY, WE HAVE CONTINUED THE TREND OF BOOSTING POPS INTO
THE 90-100% RANGE FOR A FEW HOUR PERIOD OVERNIGHT. WHILE MOST
AREAS SHOULD GET SOME RAIN FROM THIS ACTIVITY TONIGHT, IT WILL BE
A QUICK HIT OF PRECIP, WHICH WILL LIMIT OVERALL TOTALS TO BE
GENERALLY A QUARTER INCH OR LESS. NEVERTHELESS, SOME LOCALIZED
AMOUNTS OVER OF A HALF INCH TO INCH WILL BE POSSIBLE WITHIN NARROW
CORRIDORS.
THE SHOWERS WILL CLEAR THE AREA BY MID MORNING ON FRIDAY, WITH
MOST AREAS LIKELY DRY BY SUNRISE. THEREAFTER, A SEVERAL HOUR
PERIOD OF DRY WEATHER IS EXPECTED INTO THE AFTERNOON, BEFORE
ANOTHER FAST MOVING MID-LEVEL IMPULSE TRACKS INTO THE AREA LATE
IN THE DAY. LOW-LEVEL MOISTURE AND FORCED ASCENT WITH THIS SECOND
IMPULSE SHOULD BE SUFFICIENT TO SUPPORT AN ADDITIONAL ROUND OF AT
LEAST ISOLATED TO WIDELY SCATTERED SHOWERS LATE FRIDAY AFTERNOON
INTO THE EARLY EVENING HOURS, PARTICULARLY ACROSS FAR NORTHERN IL
(NORTH OF I-80). A FEW LIGHT SHOWERS MAY THEN PERSIST NEAR THE
LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WITH THE FIRST REAL COLD PUSH NOT EXPECTED TO OCCUR IN OUR AREA
UNTIL FRIDAY NIGHT, WE CAN EXPECT ANOTHER DAY OF UNSEASONABLY
MILD TEMPERATURES FOR FRIDAY, ALBEIT WITH BREEZY WESTERLY WINDS.
ACCORDINGLY, HIGH TEMPERATURES ARE SLATTED TO TOP OUT IN THE
LOW 60S IN MOST LOCATIONS, THOUGH A FEW MID 60S ARE POSSIBLE
SOUTH OF I-80. TEMPERATURES WILL THEN FALL OFF INTO THE 30S FOR
OVERNIGHT LOWS LATE FRIDAY NIGHT.
KJB
SATURDAY THROUGH THURSDAY:
THE MAIN FOCUS IS ON THE FIRST SHOT OF WINTRY WEATHER FOR OUR AREA
IN WHAT HAS BEEN A MILD AUTUMN TO DATE FROM SATURDAY NIGHT THROUGH
MONDAY.
SATURDAY THROUGH SATURDAY NIGHT:
ENSEMBLE GUIDANCE (WITH A GRADUALLY NARROWING ENVELOP OF SOLUTIONS
AND TIMING OF KEY ELEMENTS) CONTINUES TO SHOW STRONG SUPPORT FOR A
SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW BRINGING PRECIPITATION
TO OUR AREA LATER SATURDAY AFTERNOON THROUGH SATURDAY NIGHT.
MOST AREAS CAN EXPECT A DRY SATURDAY MORNING, ALBEIT WITH SKIES
BECOMING MOSTLY CLOUDY AND COOLER TEMPERATURES THAN FRIDAY'S MILD
READINGS (MID 40S NORTH TO LOWER 50S SOUTH BY EARLY AFTERNOON
SATURDAY). WITH MODERATE NORTH-NORTHEASTERLY FLOW DOWN THE LAKE
SATURDAY MORNING, SOME SPOTTY (~20% POPS) LAKE EFFECT RAIN SHOWERS
ARE POSSIBLE NEAR THE LAKE IN ILLINOIS AND INDIANA.
MID TO LATE SATURDAY AFTERNOON AND ESPECIALLY THE EVENING IS WHEN
THE BRUNT OF THE WIDESPREAD STRATIFORM PRECIP FOR OUR AREA WILL
OCCUR, NEAR AND NORTH OF THE ~1004-1007 MB SURFACE LOW TRACKING
NEAR THE I-70 CORRIDOR. WHILE MUCH COOLER AIR WILL BE MOVING IN
ALOFT, THERE'S BEEN A NOTED TREND TOWARD THE TRUE ARCTIC AIR MASS
ARRIVING SUNDAY. FOR THIS REASON, THE CHANCE FOR SUFFICIENTLY
COLD SURFACE WET BULB TEMPS FOR SNOW AND HIGHER PRECIP RATES
(IMPORTANT TO OVERCOME THE ANTECEDENT WELL ABOVE FREEZING GROUND
TEMPS) TO OVERLAP HAS TRENDED DOWNWARD. THUS, THE CHANCE FOR
ANYTHING MORE THAN A CHANGE TO SLUSHY, PRIMARILY NON-ACCUMULATING
SNOW FOR PARTS OF NORTHERN ILLINOIS PRIOR TO DAYBREAK SUNDAY HAS
ALSO DIMINISHED.
SUNDAY THROUGH MONDAY:
ON THE OTHER HAND, THE SUNDAY THROUGH EARLY MONDAY TIMEFRAME STILL
HOLDS THE POTENTIAL FOR MORE "INTERESTING", AND EVEN LOCALLY
IMPACTFUL WINTRY WEATHER. AS THE SATURDAY NIGHT SYSTEM EXITS INTO
THE EASTERN LAKES SUNDAY MORNING, A PIECE OF AN ANOMALOUSLY
DEEP/COLD PV LOBE OVER HUDSON BAY WILL DIVE SOUTHWARD INTO THE
WESTERN GREAT LAKES. THIS WILL BE CHARACTERIZED BY PROGGED 500 MB
TEMPERATURES OF AROUND -40C AND 850 MB TEMPERATURES BETWEEN -10
AND -15C AS IT SPILLS INTO THE GREAT LAKES, WHICH WOULD BE AT OR
NEAR RECORD LEVELS FOR THIS TIME OF YEAR IN SOUNDING CLIMATOLOGY
AT GRB.
THE INCOMING MID-LEVEL TROUGH AXIS PUSHING IN TOWARDS MIDDAY
SUNDAY LOOKS MORE LIKELY TO HAVE SUFFICIENT MOISTURE IN THE DGZ TO
WRING OUT TRUE SNOW SHOWERS OVER AT LEAST THE EASTERN HALF OR 1/3
OF THE CWA SUNDAY MORNING (PERHAPS LINGERING INTO THE EARLY
AFTERNOON). IN ADDITION, INCREASINGLY FAVORABLE LAKE INDUCED
THERMODYNAMICS OVER LAKE MICHIGAN WILL LIKELY ENHANCE PRECIP RATES
INTO NORTHWEST INDIANA, THOUGH STRONG ONSHORE FLOW FROM THE MILD
LAKE WOULD PROBABLY CONFINE ANY ACCUMULATIONS TO INLAND OF THE
LAKESHORE IN NORTHWEST INDIANA. ALL IN ALL, THE POTENTIAL FOR ANY
MEANINGFUL SLUSHY ACCUMULATIONS AND PAVEMENT IMPACTS DURING THE
DAY ON SUNDAY STILL LOOKS PRETTY LIMITED GIVEN MARGINAL AIR TEMPS
AND ANTECEDENT MILD PAVEMENT TEMPS.
HARSHLY COLDER TEMPS (ESPECIALLY RELATIVE TO HOW MILD IT HAS BEEN
MUCH OF THIS FALL) WILL BE THE BIGGEST STORY ON SUNDAY AFTERNOON,
WITH DECEMBER-LIKE TEMPS IN THE 30S AND BLUSTERY NORTHWEST WINDS
GUSTING TO 30-35 MPH KEEP WIND CHILLS IN THE TEENS AND 20S.
TURNING TO SUNDAY NIGHT INTO MONDAY, THE LIKELIHOOD OF IMPRESSIVE
LAKE INDUCED THERMODYNAMICS PAIRED WITH SUB-FREEZING SURFACE TEMPS
MAKES THIS THE MOST CONCERNING TIMEFRAME FROM AN IMPACTS PERSPECTIVE.
THE HUGE LOOMING QUESTION MARK IN THE GUIDANCE ENVELOPE IS THE
OVERALL MID-UPPER LEVEL TROUGH SHAPE AND EVOLUTION, WHICH WILL
AFFECT THE SURFACE PATTERN, NAMELY WITH A POTENTIAL SURFACE
TROUGH AXIS THAT COULD FORCE LAKE EFFECT/LAKE ENHANCED SNOW
FARTHER WESTWARD THAN WOULD OTHERWISE BE TYPICALLY EXPECTED.
THE NON-GFS/GEFS SUITES OF OPERATIONAL/PHYSICS-BASED GUIDANCE
CONTINUE TO BE MOST EXCITED IN THE SUNDAY NIGHT ACCUMULATING SNOW
POTENTIAL FOR PARTS OF OUR AREA (INCLUDING THE CITY OF CHICAGO
AND MUCH OF THE CHICAGO METRO IN THE MOST AGGRESSIVE DEPICTIONS).
INTERESTINGLY, THE ECMWF AIFS AND AI EPS DEPICT A MORE CLASSICAL
NORTH-NORTHWEST/NW FLOW LAKE EFFECT SETUP INTO NORTHWEST INDIANA
AND SOUTHWEST MICHIGAN. SO FOR NOW, WITH IT BEING ONLY
THURSDAY, AND THE MORE AGGRESSIVE SNOW SOLUTIONS REPRESENTING A
FAIRLY UNUSUAL/ATYPICAL OUTCOME, WILL CONTINUE TO LABEL THIS AS
A PERIOD TO WATCH IN OUR GRAPHICAL MESSAGING.
ONCE INTO THE DAYTIME HOURS OF MONDAY, REGARDLESS OF HOW SUNDAY
NIGHT-EARLY MONDAY PLAYS OUT, THERE'S BETTER AGREEMENT IN A MORE
CLASSIC NW FLOW LAKE EFFECT SETUP INTO PARTS OF LAKE AND
ESPECIALLY PORTER COUNTIES OR JUST EAST (DEPENDING ON THE EXACT BL
FLOW). FOLLOWING A HARD FREEZE FOR MOST LOCALES SUNDAY NIGHT, THE
MID NOVEMBER SUN WILL ONLY HELP TEMPS RECOVER INTO THE UPPER 30S
AWAY FROM LAKE EFFECT CLOUDS AND POSSIBLE SNOW IN PARTS OF NW IN.
MONDAY NIGHT THROUGH THURSDAY:
THE MID-UPPER PATTERN WILL QUICKLY RETURN TO DRIER, MILDER WNW
FLOW ALOFT THE REST OF NEXT WEEK AS THE PV LOBE RE-ESTABLISHES
OVER NORTHERN HUDSON BAY. THIS WILL RESULT IN TEMPS RETURNING TO
NEAR TO A BIT BELOW NORMAL BY MID TO LATE NEXT WEEK AFTER THE
ARCTIC AIR MASS GETS SHUNTED EAST TUESDAY MORNING.
CASTRO
AVIATION /00Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 547 PM CST THU NOV 6 2025
KEY MESSAGES FOR THE 00Z TAF PERIOD:
* GUSTY SSW WINDS THIS EVENING AND AND TONIGHT
* A PUSH OF SHOWERS LATE TONIGHT AND COINCIDENT MVFR CONDITIONS
POSSIBLE. A COUPLE OF THUNDERSTORMS WILL BE POSSIBLE AS WELL
* A PERIOD OF MVFR CIGS FRIDAY MORNING
SSE WINDS AROUND 10 TO 15 KT WILL VEER TO SSW LATER THIS
EVENING AND GUSTS WILL BUILD TO 20 TO 25 KT FOR THE NIGHT. GUSTS
MAY START TO BUILD OUT OF A 170-180 DIRECTION BEFORE PUSHING
WEST OF SOUTH. OCCASIONAL GUSTS AS HIGH AS AROUND 35 KT WILL BE
POSSIBLE TONIGHT. SW WINDS WILL GET AS HIGH AS 45 TO 50 KT AT 2
KFT AGL. GIVEN THE GUSTS EXPECTED AT THE SURFACE, OPTED TO OMIT
A LLWS MENTION IN THE ORD, MDW, AND GYY TAFS, WHILE LLWS WAS
MAINTAINED FOR DPA AND RFD WHERE THE SETUP LOOKS SLIGHTLY MORE
SUPPORTIVE. ANTICIPATE WESTERLY WINDS WITH GUSTS TO 20 TO 25 KT
DURING THE DAY ON FRIDAY BEFORE SUBSIDING AND GOING NNW FOR THE
EVENING.
SHOWERS WILL PUSH ACROSS THE AREA OVERNIGHT TONIGHT. PRECIP
COULD REACH RFD AS EARLY AS 04Z AND THE CHICAGO SITES AS EARLY
AS 06Z. IT'S POSSIBLE THAT A COUPLE OF EMBEDDED THUNDERSTORMS
DEVELOP. THE BEST CHANCE FOR EMBEDDED THUNDER WOULD BE 05-07Z AT
RFD AND 07-09Z AT THE CHICAGO SITES. IT'S ALSO POSSIBLE THAT
MVFR CIGS AND VSBYS ACCOMPANY THE SHOWERS, WITH A PERIOD OF MVFR
CIGS ANTICIPATED FOLLOWING THE RAIN THROUGH AROUND MID-MORNING
BEFORE SCATTERING TO VFR.
DOOM
MARINE
ISSUED AT 250 PM CST THU NOV 6 2025
THE FORECAST THINKING FOR POTENTIAL GALE FORCE GUSTS TONIGHT
HAS NOT CHANGED.
AN AREA OF LOW PRESSURE NEAR 29.5 INCHES WILL GRADUALLY DEEPEN
TONIGHT AS IT MOVES EAST ACROSS THE UPPER GREAT LAKES. SOUTHERLY
WINDS WILL INCREASE QUICKLY IN RESPONSE ACROSS THE ILLINOIS AND
INDIANA NEARSHORE WATERS THIS EVENING, WITH FREQUENT GUSTS
OVER 30 KNOTS EXPECTED. THERE IS A BRIEF WINDOW TONIGHT BETWEEN
ROUGHLY 9 PM AND 3 AM WHERE OCCASIONAL GALES TO 35 TO 40 KTS
WILL BE POSSIBLE, PARTICULARLY A FEW MILES OFFSHORE. IF
CONFIDENCE IN THE FREQUENCY OF GALE GUSTS INCREASES, A BRIEF GALE
WARNING MAY BE NEEDED DURING THIS PERIOD.
A SMALL CRAFT ADVISORY IS IN EFFECT FROM 6 PM THIS EVENING TO 6
AM FRIDAY. AN EXTENSION IN TIME TO THE ILLINOIS NEARSHORE
PORTION OF THE ADVISORY INTO FRIDAY AFTERNOON MAY ALSO BE NEEDED
IN FUTURE FORECAST UPDATES.
CARLAW/KJB
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 AM CST FRIDAY FOR THE IL AND IN
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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