331
FXUS63 KIWX 311919
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
319 PM EDT FRI JUL 31 2026
KEY MESSAGES
- CHANCE OF SHOWERS AND STORMS INCREASE FROM WEST TO EAST
TONIGHT INTO SATURDAY MORNING (60-90%). SOME AREAS MAY
EXPERIENCE A LULL IN RAIN CHANCES SATURDAY MORNING INTO EARLY
AFTERNOON, BUT SCATTERED TO NUMEROUS SHOWERS WITH SOME
THUNDERSTORMS ARE EXPECTED SATURDAY AFTERNOON INTO AT LEAST
SUNDAY MORNING. WIDESPREAD SEVERE STORMS ARE NOT EXPECTED, BUT
AN ISOLATED STRONG TO SEVERE STORM IS POSSIBLE SATURDAY
AFTERNOON AND EARLY EVENING WITH ISOLATED WIND GUSTS OF 50 TO
60 MPH POSSIBLE, ESPECIALLY SOUTH OF US ROUTE 24.
- HEAVY RAIN IS POSSIBLE SATURDAY INTO SUNDAY MORNING.
CONFIDENCE REMAINS LOW REGRADING PLACEMENT OF HIGHEST RAINFALL
AMOUNTS WITH GREATEST CHANCES OF STORM TOTAL RAINFALL AMOUNTS
IN EXCESS OF 2 INCHES (~ 50%) ALONG AND SOUTH OF US ROUTE 30
ACROSS NORTHERN INDIANA. LOCALIZED RAINFALL AMOUNTS IN EXCESS
OF 4 INCHES ARE POSSIBLE WHERE ANY PERSISTENT THUNDERSTORM
ACTIVITY CAN DEVELOP. THE GREATEST FLOOD RISK IS EXPECTED
SATURDAY NIGHT INTO EARLY SUNDAY.
- THERE IS A MODERATE SWIM RISK FOR LAKE MICHIGAN BEACHES ALONG
THE SOUTHERN BERRIEN COUNTY, MI AND LA PORTE COUNTY, IN LATE
SATURDAY AFTERNOON AND EVENING. BREAKING WAVES AND CURRENTS
ARE EXPECTED.
- THERE IS A HIGH SWIM RISK FOR BEACHES ALONG BOTH LA PORTE
COUNTY, IN AND ALL OF BERRIEN COUNTY, MI SHORELINES ON SUNDAY.
LIFE- THREATENING WAVES AND CURRENTS ARE EXPECTED. THOSE
PLANNING TO VISIT THE BEACH SHOULD STAY OUT OF THE WATER.
DISCUSSION
ISSUED AT 309 PM EDT FRI JUL 31 2026
...POTENTIAL OF HEAVY RAINFALL WITH GREATEST CONCERN SATURDAY
NIGHT/EARLY SUNDAY....
THE PRIMARY FORECAST CONCERN FOR THIS FORECAST WILL BE POTENTIAL OF
HEAVY RAINFALL, WITH GREATEST IMPACTS POSSIBLE SATURDAY NIGHT INTO
SUNDAY AM.
SOME ELEVATED MOISTURE RETURN IS APPROACHING THE IN/IL STATELINE
THIS AFTERNOON DOWNSTREAM OF A STRONGER UPPER LEVEL SHORT WAVE
TRACKING ACROSS CENTRAL IOWA. SOME FAIRLY DRY MID LEVEL AIR
PRECEDING THIS ZONE OF MOISTURE ADVECTION SHOULD LIMIT RAINFALL
THROUGH LATE THIS AFTERNOON WITH THIS INITIAL ELEVATED FORCING. A
MORE ROBUST LOW LEVEL THETA-E RIDGE WILL BUILD IN FROM NORTHEAST
ILLINOIS AFTER 03Z THIS EVENING. SOME QUESTION AS TO HOW STRONGLY
FORCED THE SETUP WILL BE LATE THIS EVENING, WITH POTENTIAL OF
MORE WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS PASSABLY
HOLDING OFF UNTIL LATE OVERNIGHT HOURS AS UPPER JET STREAK
NOSES INTO SOUTHERN GREAT LAKES WITH DEEPER MOISTURE PROFILES IN
PLACE. SOME TRIMMING OF POPS MAY BE NEEDED THIS EVENING ACROSS
CENTRAL/EASTERN PORTIONS OF THE AREA AS INITIAL MID LEVEL
MOISTURE ADVECTION FORCING OUTRUNS BETTER UPPER SUPPORT. DID
DELAY THUNDER MENTION A BIT THIS EVENING WITH LAPSE RATES
LOOKING MEAGER AS MID LEVEL MOISTENING OCCURS, WITH GREATER
THUNDER POTENTIAL LIKELY HOLDING OFF UNTIL AFTER 06Z.
SATURDAY THROUGH EARLY SUNDAY AFTERNOON STILL APPEARS TO BE MOST
POTENTIALLY IMPACTFUL PERIOD OF THIS FORECAST WITH HEAVY RAINFALL
POTENTIAL THE FIRST ORDER CONCERN FOLLOWED BY SOME MARGINAL SEVERE
THREAT SOUTH OF US 24. GUIDANCE HAS EXHIBITED SOME DRAMATIC SHIFTS
OVER PAST FEW DAYS IN THE HANDLING OF MASS FIELDS WITH THIS SYSTEM
WHICH APPEARS TO BE IN LARGE PART IN DIFFICULTY HANDLING THE
LOCATION AND STRENGTH OF THE ASSOCIATED DIABATIC PV ANOMALY ACROSS
THE MID MS VALLEY. OVERALL TREND IN 12Z GUIDANCE (ALTHOUGH STILL
WITH LARGE VARIANCE) HAS BEEN TOWARD AN INITIALLY WEAKER LOW/MID
LEVEL DIABATIC PV ANOMALY AND PREFERENCE TO MORE OF A SOUTHWARD
SUPPRESSION OF LOW LEVEL REFLECTION INTO WEST CENTRAL INDIANA BY
MIDDAY SATURDAY. SOME INDICATIONS OF A WEAK MID LEVEL DRY SLOT
FEATURE PUNCHING INTO THE AREA SATURDAY MORNING COULD PROVIDE A
LULL IN GREATER SHOWER COVERAGE, BUT STRONGER UPPER SUPPORT/DPVA
AND NORTHWARD MIGRATION OF 500-1200 J/KG MLCAPE AXIS SHOULD
ALLOW FOR CONVECTIVE REDEVELOPMENT IN THE AFTERNOON. THE
DOWNSTREAM LOW LEVEL JET INTO EAST CENTRAL INDIANA MAY BE A BIT
MORE SUBDUED AS A RESULT OF THE INITIALLY MORE SUPPRESSED
EVOLUTION TONIGHT WHICH COULD YIELD A BIT LOWER OF A SEVERE
THREAT FROM EARLIER INDICATIONS SATURDAY AFTERNOON. NO
SIGNIFICANT CHANGES NOTED IN SPC DAY 2 OUTLOOK WITH MARGINAL
RISK (MAINLY WIND) ACROSS FAR SOUTHEAST AREAS. SOME LOCALLY
HEAVY RAINFALL IS POSSIBLE SATURDAY AFTERNOON WITH GREATEST
POTENTIAL ACROSS THE SOUTH/SOUTHEAST WHERE GREATER INSTABILITY
SHOULD RESIDE AND WHERE SOME ENHANCED LOW LEVEL CONVERGENCE
FROM LOW LEVEL JET COULD BE SITUATED.
THE BIGGEST POTENTIAL IMPACT WITH THE SYSTEM FOR THIS WEEKEND IS
BEGINNING TO FOCUS MORE ON HYDROLOGY. PWAT'S OF 1.75 TO 2.00 INCHES
ARE EXPECTED TO WRAP AROUND MID LEVEL HEIGHT MINIMUM INTO THE LOCAL
AREA SATURDAY INTO SATURDAY NIGHT. THE TRACK OF THE MID/UPPER HEIGHT
MINIMUM ACROSS CENTRAL INDIANA AND SHARPENING OF LOW LEVEL TROUGH
AXIS SHOULD ALLOW A DEFORMATION-FORCED REGION TO FORM SATURDAY
NIGHT INTO EARLY SUNDAY AM. VERY STRONG LOW LEVEL MOISTURE
CONVERGENCE IS POSSIBLE FROM THE COMBINATION OF THE WEAK
SOUTHERLY FLOW ACROSS THE SOUTH AND MORE ROBUST EASTERLY FLOW
ACROSS THE SOUTHERN GREAT LAKES TO MAXIMIZE PRECIP EFFICIENCY.
WARM CLOUD DEPTHS ARE ALSO EXPECTED TO BE IN EXCESS OF 12K FEET.
SOME HIGHER RES GUIDANCE DEPICTS AN AXES OF VERY HEAVY RAINFALL
SATURDAY NIGHT AN STORM TOTAL RAINFALL AMOUNTS IN EXCESS OF 5
INCHES IN AREA OF STRONGEST DEFORMATION FORCING. SOME
CONSIDERATION WAS GIVEN THIS AFTERNOON TO ISSUING A FLOOD WATCH
FOR SATURDAY NIGHT INTO SUNDAY AM. UPON COLLABORATION, HAVE
OPTED TO HOLD OFF ON FLOOD WATCH WITH THIS ISSUANCE GIVEN
RELATIVELY DRY ANTECEDENT CONDITIONS AND VERY HIGH RUN TO RUN
VOLATILITY IN RECENT GUIDANCE WITH KEY LOW LEVEL MASS FEATURES
WHICH WILL AFFECT STRENGTH/POSITION OF DEFORMATION FORCING.
SATURDAY NIGHT/SUNDAY AM DOES INCREASINGLY LOOK LIKE A PERIOD TO
WATCH FOR HYDRO CONCERNS HOWEVER.
FORECAST CONFIDENCE IS BELOW NORMAL FOR EARLY NEXT WEEK WITH
GUIDANCE STRUGGLING IN HOW TO HANDLE RESIDUALS OF THE MID/UPPER
LEVEL SYSTEM ACROSS OHIO VALLEY IN WEAK STEERING FLOW/BLOCKING
PATTERN. DID ACCEPT BLENDED GUIDANCE TREND OF MAINTAINING POPS INTO
MIDDLE OF THE WEEK BUT THIS WILL BE SUBJECT TO CHANGE GIVEN TO LOW
PREDICTABILITY OF THIS PATTERN. A DAMPENED UPSTREAM RIDGE BY THE
MIDDLE OF NEXT WEEK VIA A SERIES OF PACIFIC WAVES WILL ALLOW
POTENTIAL OF SOME RENEWED THETA-E ADVECTION IN WAKE OF
DECAYING/DEPARTING UPPER LOW WITH ADDITIONAL CHANCES OF STORMS
WED/THU AND TREND BACK TO SEASONABLE TEMPERATURES.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 228 PM EDT FRI JUL 31 2026
OUR DRY AIR TODAY IS OVERTAKEN BY MOISTURE AS A LOW PRESSURE SYSTEM
APPROACHES CAUSING CIGS TO DROP INTO MVFR TERRITORY AND
POTENTIALLY EVEN IFR LATER TONIGHT INTO EARLY SATURDAY ALONG
WITH RAIN CHANCES. THE EASTWARD EXTENT OF MVFR COMES WITH SOME
MORE UNCERTAINTY FOR FWA AS THERE'S A CHANCE THEY DON'T END UP
WITH MVFR AT ALL DURING THIS PERIOD. HAVE HEDGED TOWARDS SOME
WITH THIS ISSUANCE, BUT IT POSSIBLE THEY GET REMOVED FOR THE
NEXT ISSUANCE. SOUTHERLY WINDS BECOME MORE EASTERLY OVERNIGHT
WITH 10 KT SUSTAINED WINDS BECOMING MORE COMMON FOR SATURDAY.
THERE COULD BE SOME SEVERE WEATHER IN THE VICINITY OF FWA
SATURDAY AFTERNOON, BUT THE EXTENT OF INSTABILITY APPEARS IN
QUESTION. GIVEN THE EXTENT OF THE MOISTURE COLUMN AND THE LOW
LEVEL TURNING OF WINDS, A BRIEF SPINUP MAY BE POSSIBLE, BUT THIS
ENVIRONMENT WOULD SEEM MORE DIFFICULT TO CREATE OTHER TYPES OF
SEVERE WEATHER HAZARDS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 PM SATURDAY TO 5 AM EDT MONDAY FOR
LMZ043-046.
DISCUSSION...MARSILI
AVIATION...ROLLER
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