432
FXUS63 KIWX 202357
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
757 PM EDT THU AUG 20 2026
KEY MESSAGES
- 30-80% CHANCES FOR RAIN AND STORMS ARRIVES FRIDAY NIGHT INTO SATURDAY.
HIGHEST CHANCES IN NORTHWEST OHIO. THE RISKS FOR SEVERE
WEATHER AND FLOODING ARE LOW.
- DANGEROUS SWIMMING CONDITIONS EXPECTED FOR SOUTHEAST LAKE
MICHIGAN BEACHES ON SATURDAY AND SUNDAY WITH HIGH SWIM RISKS
BOTH DAYS.
- DRY WEATHER RETURNS SUNDAY AND MONDAY WITH BELOW NORMAL
TEMPERATURES AND LOW HUMIDITY.
DISCUSSION
ISSUED AT 138 PM EDT THU AUG 20 2026
MAINLY DRY CONDITIONS CONTINUE, HOWEVER, ISOLATED SHOWERS AND STORMS
REMAIN POSSIBLE THROUGH SUNSET, ESPECIALLY EAST OF I-69 IN NORTHEAST
INDIANA AND NORTHWEST OHIO. A TROUGH COMING OFF OF LAKE MICHIGAN AND
A LOW DEPARTING OFF TO OUR SOUTHEAST IN OHIO SHOULD ALLOW FOR A ZONE
OF MOISTURE CONVERGENCE TO SET UP NEAR I-69 BETWEEN NOW AND 02Z
TONIGHT. SURFACE OBSERVATIONS ALREADY SHOW NORTHWEST FLOW COMING OFF
OF LAKE MICHIGAN IN NORTHERN INDIANA AND NORTHEAST/EAST FLOW OFF OF
LAKE ERIE IN NORTHWEST OHIO. VISIBLE SATELLITE IMAGERY ALREADY SHOWS
SCATTERED CUMULUS CLOUDS DEVELOPING IN THE GENERAL CONVERGENCE ZONE
AREA. WE HAVE HAD A FEW WIDELY ISOLATED SHOWERS ALREADY TODAY IN
NORTHWEST OHIO SO WE WILL HAVE TO MONITOR TO SEE IF SPATIAL EXTENT
AND COVERAGE INCREASES THROUGH SUNSET. AFTER SUNSET, EXPECT LIGHT
EASTERLY WINDS TO PERSIST OVERNIGHT WITH MOSTLY CLEAR SKIES AND LOWS
NEAR 60 DEGREES.
THE NEXT CHANCES FOR RAIN AND STORMS COMES WITH A COLD FRONTAL
PASSAGE ON SATURDAY. AN UPPER LEVEL TROUGH WILL DIG THROUGH THE
GREAT LAKES STARTING FRIDAY AFTERNOON, WITH AN ATTENDANT COLD FRONT
SWEEPING THROUGH THE FORECAST AREA DURING THE DAY SATURDAY.
SCATTERED RAIN AND STORMS AHEAD OF THE FRONT ARRIVE IN NORTHWEST
INDIANA AND SOUTHWEST LOWER MICHIGAN AROUND 06Z, GRADUALLY BECOMING
MORE NUMEROUS EASTWARD INTO NORTHWEST INDIANA AND NORTHWEST OHIO AS
THE UPPER LEVEL TROUGH AMPLIFIES DURING THE MORNING AND AFTERNOON.
HAVE MAINTAINED POPS BETWEEN 30-80% ON SATURDAY, WITH THE HIGHEST
CHANCES IN NORTHWEST OHIO. GIVEN A MORE DIURNALLY FAVORABLE
TIMEFRAME EAST OF I-69, A CORRIDOR OF UP TO 1500 MUCAPE AND 25-30
KTS OF 0-6 KM SHEAR WILL SUPPORT STORMS CAPABLE OF GUSTY WINDS AND
SMALL HAIL, ALTHOUGH SEVERE WEATHER IS NOT EXPECTED AT THIS TIME.
ISOLATED TO SCATTERED LAKE EFFECT SHOWERS MAY PERSIST DOWNWIND OF
LAKE MICHIGAN WITH NORTHWEST FLOW BEHIND THE FRONT LATE SATURDAY
NIGHT INTO EARLY SUNDAY.
HIGH PRESSURE BUILDS INTO THE GREAT LAKES AND MIDWEST REGIONS AGAIN
BY SUNDAY. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL ON SUNDAY AND
MONDAY WITH HIGHS IN THE LOW TO MID 70S WITH NORTHWEST FLOW BEHIND
THE COLD FRONTAL PASSAGE. A FEW CRISP NIGHTS ARE AHEAD SUNDAY NIGHT
AND MONDAY NIGHT WITH LOWS IN THE LOW TO MID 50S. WITH MUCH DRIER
AIR BUILDING IN, DEWPOINTS ONLY IN THE 50S WILL MAKE FOR SEVERAL
NICE DAYS! ANOTHER COLD FRONT MOVES IN WEDNESDAY WITH LOW CHANCES
(20-30%) FOR RAIN/STORMS MAINTAINED.
DESPITE PLEASANT WEATHER CONDITIONS EXPECTED ON SUNDAY, IT WILL BE A
DANGEROUS DAY TO HEAD TO THE BEACH. THE AFOREMENTIONED FRONTAL
PASSAGE IS EXPECTED TO STIR UP SOUTHERN LAKE MICHIGAN, GENERATING
LARGE WAVES AND DANGEROUS CURRENTS THROUGHOUT THE WEEKEND.
NORTHWEST, ONSHORE FLOW WILL ALLOW FOR WAVES TO BUILD TO 3 TO 5 FEET
WITH STRONG CURRENTS EXPECTED. HIGH SWIM RISKS WILL BE IN PLACE BOTH
DAYS THIS WEEKEND. HEED BEACH FLAGS/LIFEGUARDS AND STAY OUT OF THE
WATER! A BEACH HAZARDS STATEMENT WILL LIKELY BE NEEDED AS WE GET
CLOSER TO THE WEEKEND AND CONFIDENCE INCREASES IN THE WIND/WAVE
FORECAST.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 754 PM EDT THU AUG 20 2026
AN INVERTED LOW LEVEL TROUGH FEATURE HAS BEEN A FOCAL POINT FOR
ISOLATED SHOWERS ACROSS NORTHEAST INDIANA THIS EVENING.
ADDITIONAL DEVELOPMENT HAS LARGELY BEEN GUIDED BY OUTFLOW
BOUNDARIES FROM THESE SHOWERS ALONG A WEAK SURFACE BASED
INSTABILITY AXIS ACROSS NORTHEAST INDIANA. PROGRESSION OF THIS
OUTFLOW REINFORCED BOUNDARY HAS TAKEN FAVORED AREAS FOR SHOWER
DEVELOPMENT SOUTH OF KFWA, AND NO ADDITIONAL SHOWERS ARE
EXPECTED IN KFWA VICINITY THIS EVENING. MOSTLY CLEAR SKIES,
LINGERING LOW LEVEL MOISTURE, AND WET GROUND FROM RECENT
RAINFALL MAY LEAD TO SOME PATCHY SHALLOW FOG FORMATION ONCE
AGAIN EARLY FRIDAY MORNING WITH PREFERRED AREA AT THIS TIME
APPEARING TO BE GENERALLY ALONG AND SOUTH OF THE US ROUTE 24
CORRIDOR. NO CHANGES HAVE BEEN MADE TO PREVIOUS TAF INCLUSION OF
MVFR VSBYS AT KFWA EARLY FRIDAY MORNING. SOME PATCHY IFR/MVFR
LOW CLOUDS ARE ALSO POSSIBLE BEFORE DAYBREAK, BUT CONFIDENCE IN
CIGS WAS TOO LOW TO INCLUDE AT THIS TIME. A MID LEVEL TROUGH
WILL TRACK ACROSS THE AREA ON FRIDAY WITH SOME INCREASE IN MID
LEVEL CLOUDS EXPECTED. CANNOT COMPLETELY RULE OUT AN ISOLATED PM
SHOWER (< 10 PERCENT COVERAGE) ACROSS NE INDIANA GIVEN
POSSIBILITY OF WEAK SFC BASED INSTABILITY, BUT WE WILL NOT
LIKELY HAVE A FOCUSING MECHANISM QUITE AS DISTINCT AS TODAY'S
INVERTED TROUGH FEATURE. THUS, DRY TAFS HAVE BEEN MAINTAINED
THIS CYCLE. WINDS WILL REMAIN ON THE LIGHT SIDE THROUGH THE
PERIOD AS A SFC RIDGE AXIS BUILDS ACROSS THE AREA.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...JOHNSON
AVIATION...MARSILI
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