158
FXUS63 KIWX 151511
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1111 AM EDT TUE SEP 15 2026
KEY MESSAGES
- HOT AND HUMID TODAY AND WEDNESDAY. SHOWER AND THUNDERSTORM
CHANCES RETURN THIS AFTERNOON THROUGH WEDNESDAY (40 TO 70%).
CHANCES MAY LINGER INTO THURSDAY AS WELL.
- THERE IS A MARGINAL RISK FOR ISOLATED STRONG TO SEVERE STORMS
BETWEEN 6 PM EDT THIS EVENING AND MIDNIGHT. MAIN THREAT IS
DAMAGING WINDS IF STORMS BECOME SEVERE. CONFIDENCE REMAINS LOW
AT THIS TIME.
- THERE IS A MODERATE SWIM RISK FOR LAKE MICHIGAN BEACHES ALONG
THE BERRIEN CO, MI SHORELINE TODAY. BREAKING WAVES AND
CURRENTS EXPECTED.
UPDATE
ISSUED AT 1111 AM EDT TUE SEP 15 2026
WARM FRONT IS MAKING STEADY PROGRESS FROM SW TO NE ACROSS THE
AREA. WIDELY SCATTERED SHOWERS AND STORMS CONTINUE TO DEVELOP
AND MOVE NE ACROSS OUR FAR N/NW COUNTIES, BUT STRUGGLE TO
MAINTAIN THEMSELVES WITH LIMITED INSTABILITY AND SUPPORT AS WE
AWAIT SOMEWHAT MORE FAVORABLE CONDITIONS THIS AFTERNOON AND
EVENING. MODEL TRENDS STILL SEEM TO POINT TOWARDS ANY NEW
DEVELOPMENT POSSIBLY HOLDING OFF UNTIL CLOSER TO 00Z OR
POTENTIALLY AFTER, WHICH WOULD ALSO LIKELY LIMIT OR END ANY
MARGINAL SEVERE THREAT WITH HYDRO POSSIBLY BECOMING A LARGER
CONCERN. HAVE MADE SOME CHANGES LOWERING POPS SOMEWHAT INTO
TONIGHT GIVEN LOW CONFIDENCE IN EVOLUTION. ONCE TRENDS BECOME
MORE APPARENT, THEN ADJUSTMENTS CAN BE MADE.
WITH THE CLOUD COVER IN THE NW AND N DID NUDGE TEMPS DOWN A BIT
AND ALSO LOWERED JUST A HAIR IN THE SW WITH QUESTIONS REMAINING
IF ANYONE SEES 90 DEGREES.
DISCUSSION
ISSUED AT 607 AM EDT TUE SEP 15 2026
A MORE UNSETTLED PATTERN BEGINS TODAY AS A LOW PRESSURE SYSTEM (OVER
ONTARIO) BRINGS A WARM FRONT THROUGH OUR AREA THIS AFTERNOON, AND
THEN A COLD FRONT THIS EVENING INTO THE OVERNIGHT HOURS. THIS COLD
FRONT WILL EVENTUALLY STALL OUT AS THE SURFACE LOW/UPPER FORCING
LIFT FURTHER INTO QUEBEC. AS OF THIS WRITING, BETTER MOISTURE
TRANSPORT IS JUST TAKING AIM INTO OUR AREA. THE WARM FRONT IS
CURRENTLY DRAPED FROM WI (NEARLY OCCLUDED) SOUTH INTO CENTRAL IL AND
INTO TN/KY. EXPECT THIS TO LIFT NORTHEAST THROUGH THE AFTERNOON. I
SUSPECT WITH ADDITIONAL MOISTURE MOVING IN TOWARDS THE 12-15Z TIME
FRAME THAT WE'LL SEE A FEW SHOWERS AND MAYBE AN ISOLATED T-STORM
FOCUSED UP NEAR LAKE MI INITIALLY, SPREADING EASTWARD WITH A FOCUS
NEAR THE TOLL ROAD. MOST OF THE HIGH RES SUGGEST THESE WILL
TAPER OFF WITH TIME OR EVEN STAY LIMITED TO THE LAKE MI AREA AND
NEAR CASS/BERRIEN/ST. JOSEPH CO, MI. THERE IS STILL RIDGING
ALOFT AND HIGH PRESSURE AT THE SURFACE, SO HOW MUCH MOISTURE
GETS INTO THIS AREA EARLY WILL DETERMINE HOW THE SHOWERS EVOLVE.
THE NAM IS THE MOST AGGRESSIVE WITH THIS LINE OF SHOWERS/STORMS
EXTENDING FROM NORTHERN IL/SOUTHERN WI INTO THE THUMB AREA OF
MI, HAVING IT CONTINUE SOUTHEASTWARD THROUGH THE MORNING AND
EARLY AFTERNOON, GRADUALLY SHIFTING IT SOUTHWARD AS IT RUNS INTO
THE RIDGE. OTHER MODELS KEEP IT MORE LIMITED AND FOCUSED
FURTHER NORTH. FOR NOW, HAVE POPS OF 20-50% FOR AREAS
ALONG/NORTH OF US 24, INCREASING WITH NORTHWESTWARD EXTENT. HAVE
AROUND 55-65% FOR BERRIEN COUNTY, MI. DON'T EXPECT ANY SEVERE
WEATHER WITH THIS EARLIER ACTIVITY IF IT SURVIVES. RIGHT NOW
FROM RADAR IT LOOKS AS IF THE OUTFLOW IS MOVING SOUTHEASTWARD
AHEAD OF THE STORMS, SO THAT WILL CERTAINLY KEEP THINGS LIMITED
(IN ADDITION TO UNFAVORABLE TIMING GIVEN NO
INSTABILITY/CAPPING). SPC HAS OUR CWA IN A MARGINAL RISK FOR
STRONG- SEVERE STORMS FOR THE TODAY/TONIGHT PERIOD. THIS IS A
HIGHLY CONDITIONAL THREAT AS IT WILL DEPEND ON HOW THE EARLIER
PART OF THE DAY EVOLVES. MORE SHOWERS AND CLOUD COVER IN THE
WEST/NORTH COULD LIMIT OUR INSTABILITY. FURTHERMORE, THE TIMING
OF THE MAIN COLD FRONT IS SLOWER THAN PREVIOUS FORECASTS (AROUND
00Z ITS JUST SOUTHEAST OF LAKE MI). WE COULD SEE SOME STORMS
POPPING AROUND 6-8 PM ET IN THE WEST (PERHAPS LINGERING
BOUNDARIES AS WELL AS ANY LAKE BREEZE COULD TRIGGER THINGS), AND
IF THEY ARE ABLE TO TAP INTO DECENT INSTABILITY WE COULD SEE A
SEVERE THREAT. HOWEVER, THE BETTER POTENTIAL REALLY FOCUSES
BETWEEN 8 PM ET TO MIDNIGHT AS THE COLD FRONT MOVES IN WHILE WE
HAVE SOME INSTABILITY AND THE BEST FORCING. THE MAIN THREAT
WOULD BE DAMAGING WINDS (SPC HAS 5%), WITH HEAVY RAIN AND
FREQUENT LIGHTNING. ML CAPE LOOKS TO BE AROUND 1000-1500 J/KG IN
THE EVENING (BEST WEST) AND AROUND 25-40 KNOTS OF 0-6 KM BULK
SHEAR. CONFIDENCE IS LOW (ESPECIALLY EAST OF I 69), AS WE HAVE
POTENTIAL FOR EARLIER SHOWERS/STORMS/CLOUD DEBRIS, PALTRY MID
LEVEL LAPSE RATES (5-6C/KM) AND THE FRONT IS DIMINISHING WITH
TIME AS IT RUNS INTO THE RIDGE. HAVE CHANCES FOR SHOWERS AND
STORMS TONIGHT IN THE 50-80% RANGE. HIGH TEMPERATURES WILL
LARGELY BE IN THE LOW-MID 80S, WITH POTENTIAL FOR HIGH 80S,
LOWER 90S FURTHER SOUTH AND WEST. HEAT INDICES LOOK TO BE 95-99
DEGREES FOR THESE AREAS AS HUMIDITY INCREASES THIS
AFTERNOON...BUT CONFIDENCE FOR ANY KIND OF ADVISORY WAS TOO LOW
GIVEN LIMITED DURATION AND ALSO BECAUSE IF THE MORE AGGRESSIVE
NAM IS CORRECT, WE COULD HAVE SOME SHOWERS/STORMS/CLOUD COVER
THAT LIMITS DAYTIME HEATING.
SHOWER AND STORM CHANCES WILL PERSIST THROUGH THE WEEKEND, WITH OUR
LINGERING STALLED FRONT BECOMING MORE E-W ORIENTED AND FLOW ALOFT
ZONAL TO SLIGHTLY TROUGHED. THIS LOWERS OVERALL FORECAST CONFIDENCE
AS WE ARE SUSCEPTIBLE TO ANY SHORTWAVES THAT RIPPLE THROUGH THE
FLOW, SO TIMING IS DIFFICULT TO PIN DOWN. HOWEVER, FOR WED-THU,
HAVE 50-70% CHANCES THAT DIMINISH TO 20-40% FRIDAY-FRI NIGHT.
ADDITIONAL POTENTIAL RETURNS AS ANOTHER COLD FRONT DROPS INTO
THE AREA SAT/SAT PM INTO EARLY SUN, SO HAVE POPS OF 30-60
PERCENT FOR THE MOST PART. HIGHS WILL BE IN THE 70S, LOW-MID 80S
FOR THE MAJORITY OF THE PERIOD, WITH A COUPLE DAYS SEEING UPPER
80S FURTHER SOUTH. BY SUNDAY, HIGHS ARE IN THE 70S.
MODERATE SWIM RISK FOR LAKE MI BEACHES IN BERRIEN CO, MI TODAY.
BREAKING WAVES AND CURRENTS ARE EXPECTED. WAVES OF 2-3 FT WILL
SUBSIDE TO 1-2 FT LATER THIS AFTERNOON. THERE WILL LIKELY BE
A MODERATE LONGSHORE CURRENT MOVING SOUTH TO NORTH ALONG THE
SHORE (AS WINDS SHIFT SOUTHWEST), WITH MODERATE-STRONG
STRUCTURAL CURRENTS ON THE SOUTH SIDES OF PIERS AND BREAKWALLS.
RIP CURRENTS ARE POSSIBLE, BUT LESS LIKELY GIVEN FAIRLY SHORE
PARALLEL FLOW.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 720 AM EDT TUE SEP 15 2026
PREDOMINANTLY VFR TO MVFR CONDITIONS AT THE TERMINALS THIS
PERIOD. SHOWERS AND ISOLATED T-STORMS IMPACT KSBN THIS
MORNING ASSOCIATED WITH WARM AIR ADVECTION/SURFACE OUTFLOW
BOUNDARY FROM STORMS OVER LAKE MI (SHOULD ARRIVE AROUND
11:45Z-12Z). OTHERWISE, MOSTLY DRY UNTIL LATER THIS
AFTERNOON/EVENING (KSBN) AND TONIGHT (KFWA) AS A COLD FRONT
MOVES THROUGH. S-SE WINDS WILL SHIFT MORE S-SW THROUGH THE DAY,
THEN BECOME LIGHT AND VARIABLE OVERNIGHT. MVFR CEILINGS/POSSIBLY
IFR ARE MORE LIKELY AT KSBN LATE TONIGHT BEHIND THE COLD FRONT,
WITH BR SETTLING IN ONCE RAIN DIMINISHES. MUCH OF THE GUIDANCE
HAS CEILINGS AROUND 1500-2500FT, BUT THERE ARE A COUPLE THAT
SUGGEST A PERIOD OF 700FT CEILINGS. KEPT AROUND 1500FT FOR NOW
GIVEN LOW CONFIDENCE. HAVE CHANCES FOR SHOWERS AND STORMS LATE
TONIGHT AT KFWA, WITH CEILINGS NOT DROPPING UNTIL LATER IN THE
PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR LMZ043-
046.
UPDATE...FISHER
DISCUSSION...MCD
AVIATION...MCD
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