550
FXUS63 KIWX 080007
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
707 PM EST FRI NOV 7 2025
KEY MESSAGES
- MORE WIDESPREAD RAIN IS EXPECTED SATURDAY NIGHT INTO EARLY
SUNDAY, ESPECIALLY NORTH OF US-24. RAIN MAY MIX WITH OR CHANGE
ENTIRELY TO SNOW SUNDAY MORNING 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.
- TEMPERATURES WILL TREND BACK TO SEASONABLE TEMPERATURES BY THE
END OF THE WEEK AND HAVE A GOOD CHANCE TO REACH 40 DEGREES ON
TUESDAY. AS A RESULT, SNOW SHOULD BE ABLE TO MELT.
DISCUSSION
ISSUED AT 257 PM EST FRI NOV 7 2025
WITHIN THIS POSITIVE PACIFIC NORTH AMERICAN (PNA) PATTERN, WAVE
BREAKS IN THE EASTERN PACIFIC ENHANCE A RIDGE ACROSS THE WESTERN
CONUS AND THIS HELPS TO SEND SHORTWAVES DOWN INTO THE TROUGH TO
CONTINUE TO DIG (ENHANCE) THE TROUGH ACROSS THE EASTERN CONUS.
ONE SUCH SHORTWAVE DEPARTED THE AREA THIS MORNING AND ITS ASSOCIATED
COLD FRONT USHERED IN DRIER AIR BEHIND THE MORNING SHOWERS, BUT A
SECONDARY COLD FRONT COMES DOWN THE LAKE AND THE MOISTURE ADVECTION
OUT IN FRONT ALONG WITH AN AREA OF INSTABILITY ALLOWS FOR A CHANCE
FOR A BRIEF PERIOD OF LAKE ENHANCED RAIN SHOWERS TONIGHT THAT END
EARLY SATURDAY AM. THAT SHORTWAVE QUICKLY LEAVES THE VICINITY OF
LAKE MI BEFORE THE NEXT WAVE ARRIVES ON THE PACIFIC JET ALONG THE
THERMAL GRADIENT LEFT BEHIND. BEHIND THE DEPARTING SHORTWAVE EARLY
SATURDAY MORNING, SURFACE WINDS TURN MORE EASTWARD AND THIS IS
EXPECTED TO PUSH THE AREA THAT RECEIVES LAKE ENHANCED RAIN FARTHER
WESTWARD AWAY FROM THE AREA BY SATURDAY MORNING. DESPITE THE FACT
THAT BY SATURDAY MORNING, TWO COLD FRONTS HAVE SWUNG THROUGH, LOW
LEVEL TEMPERATURES STAY FAIRLY SIMILAR THROUGH THE DAY SATURDAY AS
OUR NEXT LOW PRESSURE SYSTEM APPROACHES ALONG THIS GRADIENT FOR
SATURDAY AFTERNOON. THIS PROVIDES ADDITIONAL RAIN TO THE AREA INTO
SUNDAY MORNING BEFORE IT BEGINS TO MIX WITH AND POTENTIALLY
CHANGEOVER TO SNOW IN A FEW SPOTS (WITH WET BULBS DROPPING TO
FREEZING) SUNDAY MORNING INTO THE AFTERNOON. ALL TOLD, THESE SYSTEMS
PROVIDE AN ADDITIONAL 0.25 TO 0.5 INCH RAINFALL TO THE AREA BETWEEN
THIS AFTERNOON AND SUNDAY MORNING.
AN UPPER LOW IN SOUTH-CENTRAL CANADA PINWHEELS ANOTHER SHORTWAVE
DOWN LAKE MI AND THIS IS WHAT FINALLY SENDS THE COLD AIR SOUTHWARD,
BEHIND THE PRIOR SYSTEM AS IT DEPARTS. JUST TO SHOW THIS COLD, 850
MB TEMPERATURES 00Z SATURDAY EVENING START AT -1C OVER SBN AND
DECREASE TO -8.5C SUNDAY EVENING WITH A 1040 MB HIGH PRESSURE
SYSTEM CENTERED OVER THE DAKOTAS. THERE IS STILL QUITE A BIT OF
UNCERTAINTY WITH THE MODELING OF THIS LAKE EFFECT EVENT. ON
SOUTHERLY WINDS, THE LAKE EFFECT SNOW BAND BEGINS TO MOVE INTO
THE LAPORTE AREA BETWEEN 4AM AND 9AM (WIDE TIME RANGE BECAUSE OF
THE UNCERTAINTY). TRAJECTORIES BECOME MORE NORTHWESTERLY
THROUGH THE DAY SUNDAY SO EXPECT THE BANDING TO PIVOT EASTWARD.
THE MAIN VERY VIGOROUS VORT MAX AND ASSOCIATED UPPER LOW ARRIVES
SUNDAY NIGHT, BUT THERE'S STILL QUITE A BIT OF UNCERTAINTY IN
THE TRACK THAT THAT VORT MAX TAKES. THE 00Z ECMWF/GEM KEPT THE
UPPER LOW WEST WHEREAS THE 6Z GFS/NAM WERE FARTHER EAST. IT IS
INTERESTING TO SEE THE 12Z NAM/GFS COME IN FARTHER WEST WITH THE
UPPER LOW ENERGY IN BETWEEN THESE TWO CAMPS. LAKE INDUCED
INSTABILITY INCREASES FROM 250 J/KG OF CAPE TO 850 J/KG OF CAPE
WITH DELTA TS REACHING 25 TO 35 DEGREES AND THIS INCREASES THE
CHANCES FOR HEAVIER RATES DOWNSTREAM AND A POSSIBLE MESOLOW (AT
LEAST ECMWF/GEM) FORMATION. HEAVIER SNOW RATES MAKING IT INLAND
WILL DEPEND ON WHETHER OR NOT THERE'S BREAKS IN THE BANDING TO
MAKE IT MORE CELLULAR AND ALLOW DRIER AIR TO ENTRAIN IN. THIS
TIME OF YEAR, GIVEN THE WARMER ROADWAYS, IT PROBABLY IS GOING TO
TAKE HEAVIER SNOW RATES TO OVERCOME MELTING DESPITE
TEMPERATURES FALLING BELOW FREEZING SUNDAY NIGHT. IT'LL BE
INTERESTING TO SEE HOW CLOUD COVER PLAYS A ROLE IN WARMING OF
HIGH TEMPERATURES ON MONDAY, IF CAA CAN KEEP THE AREA BELOW
FREEZING OR NOT, AND WHETHER OR NOT MELTING CAN OCCUR MONDAY
DURING THE DAYTIME. ONE INTERESTING THING IS THAT SBN HAS HAD
LOW TEMPS WITHIN 5 DEGREES OF FREEZING AS FAR BACK AS 10/30 SO
PERHAPS THAT COULD PLAY A ROLE IN IF SNOW COULD STICK OR NOT.
THOSE FREEZING AND ABOVE TEMPERATURES ON MONDAY POTENTIALLY CAUSING
MELTING AND STANDING WATER COULD ALLOW FOR SOME REFREEZING AS
TEMPERATURES DROP BACK DOWN INTO THE 20S, BUT WE'LL HAVE TO SEE HOW
MUCH MOISTURE/SNOW IS LEFT OVER ON ROADWAYS. AS THE TROUGH PIVOTS
EASTWARD, IT IS EXPECTED THAT WIND GUSTS PICK UP AND THIS SHOULD
HELP AUGMENT DRYING SO IT IS POSSIBLE THAT REFREEZING IS A NON-
HAZARD. WITHIN THE UPPER NORTHWEST FLOW, A SHORTWAVE DOES TRAVERSE
THE SOUTHERN PART OF LAKE MI TUESDAY MORNING AND SO MODELS APPEAR TO
PUMP OUT SOME LIGHT PRECIPITATION ON LOW LEVEL SOUTHWEST WINDS.
TEMPERATURES ARE EXPECTED TO WARM BACK UP ABOVE FREEZING, WITH UPPER
30S TO LOW 40S FORECAST FOR HIGHS ON TUESDAY AS WAA ENSUES.
HEIGHT RISES TAKE OVER AS SOON AS MONDAY NIGHT, WHICH COULD AFFECT
THE CHANCES FOR TUESDAY'S PRECIP. BUT SFC HIGH PRESSURE TO THE SOUTH
NOSES IN PROVIDING DRY WEATHER THROUGH THE END OF THE WEEK. HIGHS
TREND BACK TOWARD SEASONABLE TEMPS AS WELL.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 622 PM EST FRI NOV 7 2025
A SHORT WAVE WITH ASSOCIATED COLD FRONTAL BOUNDARY WILL PUSH
INTO THE REGION OVERNIGHT TONIGHT. WE WILL SEE A REDUCTION IN
CIGS IN THE FORM OF SOME STRATOCUMULUS FOR BOTH TAF SITES AFTER
05Z SAT FOR KSBN AND AFTER 12Z SAT FOR KFWA HOWEVER FOR THE MOST
PART VFR CATS ARE EXPECTED BUT MAY SEE PERIODS WITH SLIGHTLY
FURTHER DROPS INTO MVFR LEVELS WITH CIGS OF 2KFT TO 3KFT HEIGHTS.
WINDS EXPECTED TO VEER TO MORE NORTHEASTERLY DIRECTION BY
SATURDAY AFTERNOON AHEAD OF THE STRONGER SYSTEM MOVING INTO THE
REGION LATE SATURDAY. AFTER 01Z DID PUT SOME MENTION OF VCSH FOR
KSBN WITH SOME LAKE EFFECT RAIN SHOWERS POSSIBLE WITH THE
FRONTAL PASSAGE. OTHERWISE, AFTER 18Z SAT FOR KSBN ADDED SOME
LIGHT RAIN SHOWERS WITH THE APPROACH OF THE NEXT SYSTEM. WINDS
WILL REMAIN FAIRLY LIGHT THROUGH THIS TAF PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST SATURDAY FOR LMZ043-046.
DISCUSSION...ROLLER
AVIATION...ANDERSEN
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