765
FXUS63 KIWX 061915
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
215 PM EST THU NOV 6 2025
KEY MESSAGES
- A BAND OF MODERATE RAIN SHOWERS (ALONG WITH POSSIBLY A RUMBLE
OF THUNDER) WILL TRACK ACROSS THE REGION LATE TONIGHT THROUGH
FRIDAY MORNING. THERE IS A HIGH PROBABILITY (GREATER THAN 90
PERCENT) THAT MOST LOCATIONS WILL SEE AT LEAST ONE TENTH OF AN
INCH OF RAINFALL.
- MORE WIDESPREAD RAIN IS EXPECTED SATURDAY NIGHT INTO EARLY
SUNDAY, ESPECIALLY NORTH OF US-24. RAIN MAY MIX WITH OR CHANGE
ENTIRELY TO SNOW WITH SOME ACCUMULATIONS POSSIBLE.
- TURNING SHARPLY COLDER SUNDAY NIGHT WITH LAKE EFFECT SNOW
DEVELOPING SUNDAY NIGHT THROUGH MONDAY. WHILE DETAILS REMAIN
UNCERTAIN ON THE TIMING, PLACEMENT, AND INTENSITY OF THESE
LAKE EFFECT BANDS, THE POTENTIAL EXISTS FOR SEVERAL INCHES OF
ACCUMULATION IN FAVORED CORRIDORS FROM SUNDAY NIGHT THROUGH
MONDAY.
DISCUSSION
ISSUED AT 209 PM EST THU NOV 6 2025
AN ACTIVE MID & UPPER-LEVEL PATTERN PERSISTS W/ NUMEROUS
DISTURBANCES EXPECTED TO IMPACT THE REGION OVER THE NEXT SEVERAL
DAYS. BROAD SHORT-WAVE RIDGING ALOFT THROUGH LATE THIS EVENING WILL
GIVE WAY TO A FAST MOVING, POSITIVELY TILTED SHORT WAVE TROUGH AND
ASSOCIATED WEAK SURFACE FRONTAL ZONE TRACKING ACROSS THE CWA LATE
TONIGHT THROUGH EARLY FRIDAY. ENHANCED LOW-LEVEL CONVERGENCE ALONG
THIS BOUNDARY COUPLED WITH AMPLE (100-110 KNOT) JET ENERGY ALOFT
SUGGESTS A BAND OF MODERATE SHOWERS (AND PERHAPS A RUMBLE OF THUNDER
GIVEN SUCH STEEP LAPSE RATES ALOFT) WILL TRAVERSE THE AREA W/ THE
MOST LIKELY TIME FRAME RANGING FROM AROUND 09Z IN THE NORTHWEST TO
15Z IN THE SOUTHEAST, VERY LITTLE CHANGE FROM PREVIOUS FORECAST
THINKING. LATEST HREF DATA SUGGESTS AROUND A 95 PERCENT PROBABILITY
OF AT LEAST ONE TENTH OF AN INCH OF RAINFALL W/ THIS BRIEF SHOT OF
MOISTURE, AND PROBABILITIES RANGING FROM 50 TO 70 PERCENT FOR THE
0.25 INCH THRESHOLD. CONFIDENCE IS VERY HIGH THAT MOST OF THE AREA
WILL SEE MEASURABLE RAINFALL BETWEEN TONIGHT AND LATE FRIDAY
MORNING. DO NOT EXPECT THIS WEAK COLD FRONTAL PASSAGE TO HAVE MUCH
OF AN IMPACT ON DAYTIME HIGHS FRIDAY GIVEN THAT THERE WILL BE PLENTY
OF TIME FOR THE AIR MASS TO RECOVER. WIDESPREAD LOWER 60S CAN
STILL BE EXPECTED FOR HIGHS, BUT ENJOY IT WHILE IT LASTS.
OUR FOCUS WILL QUICKLY SHIFT TO A MAJOR PATTERN CHANGE AS DEEP
TROUGHING TAKES SHAPE OVER THE UPPER MIDWEST COURTESY OF A VERY
STRONG (130-140 KNOT) H25 JET DIGGING ALONG THE FRONT RANGE OF THE
ROCKIES ON SATURDAY. THIS JET ENERGY ROUNDS THE BASE OF THE TROUGH
AND BECOMES FOCUSED ACROSS SOUTHERN IL/IN ON SATURDAY NIGHT WITH AN
ATTENDANT SURFACE LOW EXPECTED TO TRACK ROUGHLY ALONG US-24. COULD
SEE A DECENT BAND OF SYNOPTIC / FRONTOGENETICALLY FORCED
PRECIPITATION JUST TO THE NORTH OF THE AFOREMENTIONED LOW TRACK
(MAINLY NORTH OF US-24) LATE SATURDAY NIGHT INTO EARLY SUNDAY
MORNING. GEFS MEMBERS SHOW H85 TEMPERATURES FALLING RAPIDLY BETWEEN
00Z AND 12Z SUNDAY W/ POTENTIAL FOR < 0 DEG C WHILE THE HEAVIEST
PRECIPITATION WOULD BE ONGOING. WILL NEED TO MONITOR CLOSELY FOR THE
POTENTIAL FOR SEVERAL INCHES OF ACCUMULATION IF ALL INGREDIENTS COME
TOGETHER AT THE RIGHT TIME AND SURFACE WET BULBS CAN COOL FAST
ENOUGH. AT A MINIMUM, A RAIN/SNOW MIX IS LIKELY WITH AT LEAST A 50
PERCENT PROBABILITY OF AT LEAST 0.5 INCH OF LIQUID EQUIVALENT QPF
PER THE LATEST NBM MEMBERSHIP SUITE.
MORE PERSISTENT LAKE-EFFECT SNOW APPEARS MOST LIKELY DURING THE
SUNDAY NIGHT THROUGH MONDAY EVENING TIME FRAME AS VERY COLD NORTH-
NORTHWESTERLY LOW LEVEL FLOW SETS UP ALONG LAKE MICHIGAN WITH H85
TEMPERATURES PLUNGING TO NEAR -10 DEG C ABOVE A STILL VERY WARM LAKE
SURFACE (LAKE-H85 DIFFERENCE AROUND 20 C), COURTESY OF YET
ANOTHER (THIS TIME RATHER VIGOROUS) SHORT WAVE DIVING ACROSS THE
WESTERN GREAT LAKES DURING THE DAY ON SUNDAY. WHILE IT IS
DIFFICULT TO IRON OUT ANY SPECIFICS AT THIS TIME RANGE, THIS
DOES APPEAR TO BE SOMETHING TO WATCH OVER THE NEXT SEVERAL DAYS.
THE LATEST NBM SHOWS ROUGHLY 60 PERCENT PROBABILITIES OF 4+
INCHES OF 24-HOUR SNOWFALL ACCUMULATION ACROSS BERRIEN, LA
PORTE, AND ST. JOSEPH (IN) COUNTIES. FURTHER, LATEST ECMWF EFI
SHOWS VALUES OF AROUND 0.9 DOWNWIND OF LM WITH SHIFT OF TAILS
(SOT) VALUES OF 2 TO 5. THIS WOULD GENERALLY INDICATE GREATER
CONFIDENCE IN POTENTIAL FOR A MORE SIGNIFICANT EVENT RELATIVE TO
CLIMATOLOGY. STAY TUNED.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1225 PM EST THU NOV 6 2025
A LOW LEVEL RIDGE AXIS WILL DEPART TO THE EAST TODAY, ALLOWING
FOR SOUTHERLY FLOW THROUGH THE REMAINDER OF THE DAY. AS
BOUNDARY LAYER WINDS STRENGTHEN A BIT LATE THIS AFTERNOON, SOME
GUSTS TO AROUND 15 KNOTS ARE POSSIBLE BEFORE THESE GUSTS EASE
EARLY EVENING. LOW LEVEL FLOW WILL THEN STRENGTHEN THIS EVENING
IN ADVANCE OF THE NEXT SHORT WAVE TROUGH ACROSS THE MID MS
VALLEY. LOW LEVEL HEIGHT GRADIENT SHOULD STRENGTHEN THIS EVENING
AND THERE COULD BE JUST ENOUGH LOW LEVEL MIXING TO SUPPORT GUSTS
TO 20 TO 25 KNOTS DURING THE OVERNIGHT HOURS. DEVELOPMENT OF A
LOW LEVEL JET SHOULD SUPPORT LLWS CONDITIONS IN THE 05Z-12Z
TIMEFRAME AND WILL MAINTAIN THIS MENTION FROM THE PREVIOUS TAF
ISSUANCE. PRE-FRONTAL MOISTURE AND STEEPENING MID LEVEL LAPSE
RATES WILL SUPPORT SHOWER DEVELOPMENT TO THE WEST OF THE
TERMINALS LATER THIS AFTERNOON, AND THESE RAIN SHOWERS SHOULD
SHIFT ACROSS THE TERMINALS LATE TONIGHT INTO FRIDAY MORNING.
ISOLATED THUNDER IS POSSIBLE, BUT CONFIDENCE REMAINS TOO LOW
FOR TAF INCLUSION AT THIS TIME. CIGS MAY DETERIORATE BRIEFLY TO
BELOW 2K FEET EARLY FRIDAY IN ASSOCIATION WITH THE BEST PRE-
FRONTAL MOISTURE AND IN VICINITY OF THE COLD FRONT, BUT WILL
CARRY CIGS JUST ABOVE FUEL ALTERNATE CRITERIA WITH THE 18Z TAFS.
GUSTY WESTERLY POST-FRONTAL WINDS ARE EXPECTED ON FRIDAY
(GUSTING TO AROUND 25 KNOTS) WITH CONDITIONS IMPROVING TO VFR
FROM WEST TO EAST AS DRIER LOW LEVEL AIR BUILDS IN.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 AM EST
SATURDAY FOR LMZ043-046.
DISCUSSION...HAMMER
AVIATION...MARSILI
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page