107
FXUS63 KIWX 131742
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
142 PM EDT SUN SEP 13 2026
KEY MESSAGES
- SCATTERED SHOWERS LIKELY MAINLY IN NORTHWEST INDIANA AND FAR SOUTHWEST
LOWER MICHIGAN LATE THIS AFTERNOON INTO THE EVENING.
- THERE IS A HIGH SWIM RISK FORECAST THROUGH LATE TONIGHT FOR SOUTHEAST
LAKE MI BEACHES. DANGEROUS SWIMMING CONDITIONS CONTINUE.
- COOLER MONDAY WITH HIGHS IN THE 70S WITH COMFORTABLE HUMIDITY
LEVELS AND SUN.
- TURNING HOT AND HUMID TUESDAY AND WEDNESDAY. RAIN AND STORMS POSSIBLE
TUESDAY AFTERNOON THROUGH WEDNESDAY WITH 30-70% CHANCES.
DISCUSSION
ISSUED AT 141 PM EDT SUN SEP 13 2026
DESPITE THE NBM HAVING NO POPS TODAY, THE HREF IS IN GOOD AGREEMENT
THAT WIDELY SCATTERED SHOWERS WILL OCCUR IN NORTHWEST INDIANA AND
SOUTHWEST LOWER MICHIGAN FROM 20Z-00Z TONIGHT AS AN UPPER LEVEL
TROUGH AND ATTENDANT 500MB SHORTWAVE THAT PASSES THROUGH THE GREAT
LAKES. RAINFALL AMOUNTS SHOULD BE LIGHT, LESS THAN 0.10" FOR MOST
LOCATIONS. SURFACE OBSERVATIONS SHOW THAT THE SURFACE COLD FRONT
ASSOCIATED WITH THIS UPPER LEVEL SYSTEM ALREADY PASSED THROUGH THE
AREA THIS MORNING. INCOMING HIGH PRESSURE BEHIND THE FRONT MEANS THE
PRESSURE GRADIENT WILL INCREASE OVER THE AREA THIS AFTERNOON AND
EVENING, WITH WIND GUSTS UP TO 20-25 MPH SUNDAY AFTERNOON AND
EVENING. STRONG NORTHWEST FLOW AND CAA BEHIND THE FRONT WILL MAKE
FOR A PLEASANT NIGHT TONIGHT WITH LOWS IN THE UPPER 40S TO LOW 50S.
A VERY FALL-LIKE DAY IS AHEAD MONDAY WITH HIGHS ONLY IN THE LOW TO
MID 70S, COMFORTABLE HUMIDITY, AND SOME FILTERED SUNSHINE AS HIGH
PRESSURE WILL BE DIRECTLY OVERHEAD.
IF YOU HAVE PLANS TO HEAD TO SE LAKE MICHIGAN BEACHES TODAY, STAY
OUT OF THE WATER! THERE IS A HIGH SWIM RISK AND A BEACH HAZARDS
STATEMENT IS IN EFFECT UNTIL 03Z MONDAY. BEHIND THE COLD FRONTAL
PASSAGE THIS MORNING, DANGEROUS SWIMMING CONDITIONS HAVE DEVELOPED
AND ARE EXPECTED TO PERSIST THROUGH TONIGHT FOR SOUTHEASTERN LAKE
MICHIGAN BEACHES IN BERRIEN AND LA PORTE COUNTIES. BUOY OBSERVATIONS
OFFSHORE OF WASHINGTON PARK BEACH AND SILVER BEACH SHOW WAVES OF 3-4
FT AS OF EARLY AFTERNOON. MODERATE TO STRONG RIP AND STRUCTURAL
CURRENTS ARE EXPECTED. HAZARDOUS SWIMMING CONDITIONS MAY OCCUR AGAIN
ON TUESDAY.
AN UPPER LEVEL RIDGE WILL BUILD ACROSS THE CENTRAL AND EASTERN CONUS
OVER THE NEXT SEVERAL DAYS. WITH WAA AND SOUTHWESTERLY MOISTURE
TRANSPORT FROM THE GULF, HEAT AND HUMIDITY WILL BUILD ON TUESDAY
UNDERNEATH THE PEAK OF THE UPPER LEVEL RIDGE OVER THE GREAT LAKES.
OUR FAR SOUTHWEST WILL BE THE WARMEST WITH TEMPERATURES IN THE LOW
90S FOR HIGHS TUESDAY AND PEAK HEAT INDICES APPROACHING HEAT
ADVISORY CRITERIA AT AROUND 97-98 DEGREES. CONFIDENCE IS LOW
FOR PEAK HEAT INDICES DUE TO CHANCES FOR RAIN/STORMS (SEE BELOW)
AND CLOUDS, SO WILL HOLD OFF ON ANY HEAT HEADLINES FOR NOW.
ANOTHER COLD FRONT APPROACHES LATE TUESDAY AND WEDNESDAY WITH ZONAL
FLOW ALOFT AS THE RIDGE GETS SUPPRESSED. HAVE MAINTAINED LIKELY
POPS OF 40-70% TUESDAY AFTERNOON THROUGH WEDNESDAY. THERE IS A
MARGINAL RISK FOR SEVERE WEATHER ON TUESDAY; ISOLATED DAMAGING
WIND GUSTS WILL BE POSSIBLE DUE TO UP TO 2000 J/KG OF SBCAPE AND
STEEPENING LOW LEVEL LAPSE RATES. WITH FORCING EXPECTED TO BE
WEAK, THIS COULD BE A LIMITING FACTOR FOR STRONG TO SEVERE
STORMS. THERE ARE STILL SOME UNCERTAINTIES WITH THIS SYSTEM IN
REGARDS TO EXACT TIMING AND PLACEMENT OF THE COLD FRONT.
RAIN/STORM CHANCES MIDWEEK WILL BE HIGHLY DEPENDENT ON WHERE THE
PERIPHERY OF THE RIDGE ENDS UP (WHICH MODEL GUIDANCE HAS
ROUTINELY STRUGGLED WITH THIS SAME SETUP IN RECENT MONTHS). THE
BOUNDARY WILL LIKELY STALL SOMEWHERE ACROSS THE GREAT LAKES OR
OHIO RIVER VALLEY AS THE UPPER LEVEL RIDGE SHIFTS EASTWARD, SO
HAVE MAINTAINED BROAD POPS MIDWEEK OF 30-50%.
GIVEN THAT THE OVERALL SYNOPTIC PATTERN THIS FALL WILL BE INFLUENCED
BY A STRONG TO POTENTIALLY HISTORIC EL NINO, GUIDANCE IS SLOWLY
TRENDING TOWARDS NEAR TO SLIGHTLY WARMER THAN NORMAL TEMPERATURES
WITH DRIER THAN NORMAL CONDITIONS FOR MID TO LATE SEPTEMBER.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 130 PM EDT SUN SEP 13 2026
A SECONDARY SHORTWAVE SWINGS THROUGH THE GREAT LAKES LATE THIS
AFTERNOON BUT LOW LEVEL MOISTURE IS VERY LIMITED AND BETTER
FORCING FOR ASCENT PASSES TO THE NORTH. A FEW SHOWERS POSSIBLE
AT KSBN (EVEN LOWER CHANCE AT KFWA) BUT CONDITIONS WILL LIKELY
REMAIN VFR. GUSTY NORTHWEST WINDS RELAX OVERNIGHT AND MAINLY
CLEAR SKIES ARE EXPECTED THROUGH THE SECOND HALF OF THE PERIOD.
FOG APPEARS UNLIKELY GIVEN DEGREE OF DRY AIR ADVECTION.
IWX WATCHES/WARNINGS/ADVISORIES
IN...BEACH HAZARDS STATEMENT UNTIL 10 PM CDT THIS EVENING FOR
INZ103.
OH...NONE.
MI...BEACH HAZARDS STATEMENT UNTIL 11 PM EDT THIS EVENING FOR
MIZ177-277.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR LMZ043-
046.
DISCUSSION...JOHNSON
AVIATION...AGD
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