364
FXUS63 KIWX 131731
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
131 PM EDT SUN SEP 13 2026
KEY MESSAGES
- CHANCES (20-30%) FOR RAIN SHOWERS AND ISOLATED THUNDERSTORMS
THIS AFTERNOON AND EVENING. SEVERE WEATHER IS NOT EXPECTED AT
THIS TIME. BREEZY WITH HIGHS IN THE 70S, LOW 80S.
- THERE IS A HIGH SWIM RISK FOR BOTH LA PORTE CO, IN AND
BERRIEN CO, MI THROUGH LATE THIS EVENING. LIFE-THREATENING
WAVES AND CURRENTS ARE EXPECTED. THOSE VISITING THE BEACHES
SHOULD STAY OUT OF THE WATER.
- COOLER AND DRY MONDAY, WITH HIGHS IN THE 70S. TURNING WARMER
AND HUMID TUESDAY AND WEDNESDAY. ADDITIONAL RAIN AND STORM
CHANCES (40-80%) TUESDAY INTO THURSDAY. THERE IS A MARGINAL
RISK FOR STRONG TO SEVERE STORMS TUESDAY AFTERNOON AND
EVENING. DAMAGING WINDS WOULD BE THE PRIMARY THREAT IN THE
STRONGEST STORMS.
DISCUSSION
ISSUED AT 557 AM EDT SUN SEP 13 2026
A COLD FRONT IS CROSSING OUR FORECAST AREA THIS MORNING, DRAPED FROM
ROUGHLY SOUTHERN ONTARIO INTO AREAS JUST SOUTHEAST OF DEFIANCE, OH,
FORT WAYNE, AND MARION, IN AS OF THIS WRITING. BEHIND THE FRONT WE
HAVE LIGHT NORTH-NORTHWEST FLOW, EXCEPT NEAR LAKE MI WHERE WINDS ARE
PICKING UP SLIGHTLY NEAR THE LAKESHORE. HAVE SOME PATCHY FOG AROUND,
MAINLY ALONG/AHEAD OF THE FRONT AT THIS TIME. VISIBILITIES AT
KGWB/KUSE/KOWX/KAOH ARE ALL LESS THAN 1 MILE (SEVERAL LESS THAN 1/2
MILE), AND EXPECT THIS TO PERSIST THROUGH AROUND SUNRISE OR UNTIL
THE FRONT MOVES THROUGH. ISSUED AN SPS FOR PATCHY DENSE FOG UNTIL
13Z FOR AREAS ROUGHLY ALONG/SOUTH OF US 24 EAST OF I 69.
OTHERWISE, NORTHWEST WINDS STRENGTHEN THROUGH THE AFTERNOON AS
SURFACE HIGH PRESSURE BUILDS IN RAPIDLY BEHIND THE EXITING COLD
FRONT. GUSTS UP TO AROUND 20-25 MPH ARE EXPECTED, ESPECIALLY NEAR
LAKE MI AND NORTH OF US 30. ACCORDINGLY, WAVES ON LAKE MICHIGAN
AROUND 2 FEET THIS MORNING SHOULD BUILD TO 3 TO 5 FEET BY EARLY
AFTERNOON, PERSISTING INTO LATE THIS EVENING. WAVES APPROACH AT A 45-
90 DEGREE ANGLE RELATIVE TO SHORE, WITH WAVE PERIODS AROUND 6
SECONDS. EXPECT A STRONG NORTH TO SOUTH FLOWING LONGSHORE CURRENT
ALONG THE BEACH, AND STRONG STRUCTURAL CURRENTS NEAR PIERS AND
BREAKWALLS (ESPECIALLY ON THE NORTH SIDE). RIP CURRENTS ARE
EXPECTED. THOSE VISITING THE BEACH SHOULD PLAN TO STAY OUT OF THE
WATER. MAINTAINED THE PREVIOUSLY ISSUED SMALL CRAFT ADVISORY/BEACH
HAZARDS STATEMENT FROM LATE THIS MORNING INTO THE LATE EVENING
HOURS.
OUTSIDE OF A LIGHT SHOWER ALONG/NEAR THE FRONT THIS MORNING, WE'LL
REMAIN DRY UNTIL THIS AFTERNOON/EVENING WHEN A SHORTWAVE MOVES
THROUGH ALOFT. SHOWERS AND MAYBE A COUPLE THUNDERSTORMS DEVELOP NEAR
AN FGEN BAND ALONG A FRONTAL ZONE IN IN THE 850-700MB RANGE OVER
IL/NW IN THAT DRIFTS SOUTHEASTWARD AND WEAKENS WITH TIME THIS
AFTERNOON/EVENING. COULD SEE A RUMBLE OF THUNDER IF WE GET STEEPER
LAPSE RATES AROUND 6-7C/KM IN MID LEVELS. OTHERWISE, MUCH OF THE
SURFACE INSTABILITY IS TO OUR SOUTHEAST (NEAR LIMA, OH AND ALONG
SOUTHERN BORDER), SO DON'T EXPECT ANY WIDESPREAD T-STORM DEVELOPMENT.
DEPENDING ON THE SPEED OF THE WAVE, PRECIPITATION/STORM CHANCES END
BY 00-3Z ALONG OUR SOUTHERNMOST BORDER IN IN/NW OH.
HIGH PRESSURE CENTERS OVER THE GREAT LAKES REGION THEN TONIGHT INTO
MONDAY NIGHT, SHIFTING EASTWARD GRADUALLY BENEATH AN AMPLIFYING
UPPER LEVEL RIDGE. THE BROAD HIGH INITIALLY IS CENTERED OVER THE SE
CONUS, AND BUILDS STRAIGHT NORTH INTO ONTARIO AT 00Z TUESDAY, THEN
BEGINS TO TILT ON THE NORTH END TOWARDS THE EASTERN SEABOARD THROUGH
WED/THU, WHICH WILL BRING US INTO A MORE ACTIVE PATTERN IN TERMS OF
SHOWERS AND STORMS. MODELS HAVE AN UPPER LEVEL LOW/SURFACE LOW
TRAVERSING THE NORTHERN PLAINS AND CANADIAN PRAIRIES, EVENTUALLY
REACHING HUDSON BAY BY TUESDAY NIGHT AND ONTO QUEBEC BY
WEDNESDAY AFTERNOON. THE UPPER LEVEL TROUGH BEGINS TO BREAKDOWN
THE NORTHWEST PERIPHERY OF THE RIDGE AS THE LOW MOVES EASTWARD,
BRINGING A SFC COLD FRONT INTO OUR FORECAST AREA BY TUESDAY
AFTERNOON/EVENING. DECENT WARM AIR ADVECTION/MOISTURE PUMPING
INTO THE AREA AHEAD OF THE FRONT BENEATH THE UPPER LEVEL RIDGE
PROVIDES US WITH AN UNSTABLE ENVIRONMENT. THE COLD FRONT HAS AN
ETA OF 18-00Z DEPENDING ON THE MODEL, WHICH WOULD BE FAVORABLE
TIMING FOR MAXIMIZING AVAILABLE INSTABILITY (NAM HAS 1500-2500
J/KG ML CAPE AROUND THIS TIME). BULK SHEAR IS ON THE ORDER OF
30-40 KNOTS, WITH THE BEST VALUES FURTHER NORTH IN MI. SPC HAS
OUR FORECAST IN A MARGINAL RISK FOR SEVERE WEATHER ACCORDINGLY.
MID LEVEL LAPSE RATES AREN'T ALL THAT GOOD (AROUND 6.5C/KM MAX),
AND IF THE FRONT ARRIVES LATER IT WON'T BE AS FAVORABLE
INSTABILITY WISE. IF WE DO HAVE SEVERE WEATHER, THE MAIN THREATS
WOULD BE DAMAGING WINDS. HIGH TEMPERATURES TUESDAY WILL BE IN
THE MID-UPPER 80S FOR MOST AREAS, WITH LOCATIONS WEST OF I 69
SOUTH OF US 30 POTENTIALLY REACHING THE LOW 90S. COOLEST IN
LOWER MI, WHERE TEMPS WILL BE IN THE LOWER 80S. HEAT INDICES
ALONG AND WEST OF I 69, SOUTH OF US 30 COULD REACH AROUND 100
DEGREES.
THE COLD FRONT WILL MOVE INTO OUR AREA AND STALL OUT, MODELS APPEAR
TO INITIALLY STALL IT OUT GENERALLY ALONG US 24 BY WEDNESDAY. AS THE
UPPER LEVEL TROUGH MOVES NORTH, THE RIDGE BUILDS BACK IN AGAIN AND
COULD FORCE THE BOUNDARY FURTHER NORTH-ORIENTING ALONG THE TOLL
ROAD. EITHER WAY, WHEREVER IT SETS UP WE'LL SEE FAVORABLE CONDITIONS
FOR SHOWER AND THUNDERSTORM ACTIVITY. FLOW BECOMES MORE ZONAL, WHICH
WILL HELP KICK OFF ANY SHOWER/T-STORMS THROUGH THURSDAY/FRIDAY. HAVE
THE BEST CHANCES (70-80%) LATE TUE AFTERNOON (FAR WEST) INTO
WEDNESDAY MORNING-BUT EXPECT VALUES AROUND 40-60% THROUGH THURSDAY.
THUNDERSTORMS ARE POSSIBLE AT TIMES IN THIS PERIOD. HIGHS WILL DROP
INTO THE MID 70S AND LOW-MID 80S WED-FRI, THEN WE'LL BE IN THE 70S
BY THE WEEKEND.
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...MCD
AVIATION...AGD
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