142
FXUS63 KIWX 171030
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
630 AM EDT MON AUG 17 2026
KEY MESSAGES
- ISOLATED SHOWERS AND STORMS WILL SLOWLY EXIT OUR AREA THIS
MORNING.
- THE NEXT CHANCE OF RAIN ARRIVES TUESDAY NIGHT INTO WEDNESDAY.
SEVERE WEATHER IS NOT EXPECTED AND THE RISK OF HEAVY RAIN IS
CURRENTLY LOW.
- THERE IS A MODERATE SWIM RISK FOR SOUTHERN LAKE MICHIGAN
BEACHES TODAY.
DISCUSSION
ISSUED AT 346 AM EDT MON AUG 17 2026
ISOLATED SHOWERS AND STORMS CONTINUE THIS MORNING THANKS TO ONE LAST
REMNANT MCV EJECTING OUT OF IA/IL AND A WEAK SURFACE COLD FRONT
CROSSING OUR CWA VERY SLOWLY. THE BEST NEGATIVE THETA-E ADVECTION
DOESN'T START UNTIL AFTER 12Z AND DOESN'T FULLY ENCAPSULATE OUR SE
CWA UNTIL LATE AFTERNOON. HAVE THEREFORE ADDED SOME LOW CHANCE POP'S
SOUTH OF US-24 THROUGH MID-AFTERNOON. NO SUBSTANTIVE IMPACTS
ANTICIPATED WITH THESE STORMS. POOR MOISTURE/INSTABILITY AND WEAK
FORCING WILL LIMIT BOTH COVERAGE AND INTENSITY. HIGHS TODAY REMAIN
IN THE MID 70S TO AROUND 80 WITH INCREASING SUN FROM NORTH TO SOUTH.
THERE WILL BE A FAIRLY SHARP GRADIENT IN DEWPOINTS/HUMIDITY FROM
LOW/MID 60S NORTH TO LOW 70S SOUTH. LOWS TONIGHT WILL BE ON THE COOL
SIDE WITH AT LEAST PARTIAL CLEARING, LIGHT WINDS, AND LOWER
DEWPOINTS YIELDING MID/UPPER 50S.
MOST OF TUE WILL REMAIN DRY BUT THE NEXT CHANCE OF RAIN ARRIVES TUE
NIGHT AS AN UPPER LOW CROSSES NORTHERN ONTARIO AND SENDS ANOTHER
COLD FRONT THROUGH THE REGION. MOISTURE RETURN AHEAD OF THIS FRONT
IS NOT GREAT GIVEN PREDOMINATELY WESTERLY FLOW AND DIURNAL TIMING
REMAINS UNFAVORABLE FOR DEEP CONVECTION, ESPECIALLY GIVEN MIDLEVEL
LAPSE RATES BELOW 6 C/KM. THERE'S STILL A LOW CHANCE STORMS COULD
SNEAK INTO OUR FAR NW PRIOR TO SUNSET TUE EVENING AND MAY POSE AN
ISOLATED THREAT FOR GUSTY WINDS AS SUGGESTED BY SOME 00Z CAM'S BUT
REGARDLESS NOT EXPECTING SEVERE WEATHER AT THIS TIME. THIS FRONT
BECOMES INCREASINGLY ORPHANED FROM PARENT FORCING BY EARLY WED AND
MOST ENSEMBLE GUIDANCE MAINTAINS SOME PRECIP CHANCES FOR AT LEAST
OUR SOUTHERN ZONES THROUGH THE DAY WED. HERE AGAIN, BOTH FORCING AND
INSTABILITY ARE ON THE MEAGER SIDE FOR AN ORGANIZED SEVERE WEATHER
THREAT. EVEN THE POTENTIAL FOR HEAVY RAIN SEEMS ON THE LOW SIDE
GIVEN LACKLUSTER MOISTURE AND FORCING. OUR SOUTHERN CWA WILL LIKELY
STILL BE HIGHLY SUSCEPTIBLE TO ANY HEAVY RAIN THOUGH AND THERE ARE
SOME HINTS IT COULD BE POSSIBLE EARLY WED THANKS TO MEAN FLOW
LARGELY PARALLEL TO THE FRONT. WILL WATCH THIS ASPECT OF THE
FORECAST CLOSELY.
HIGH PRESSURE/DRY CONDITIONS RETURN WED NIGHT AND PERSIST THROUGH AT
LEAST FRI. THE NEXT TROUGH/COLD FRONT PASSES ON SAT WITH WHAT LOOKS
TO BE LIGHT RAIN/LOW THUNDER CHANCES. THERE IS STILL A LOT OF SPREAD
ON HOW EXACTLY THIS WEEKEND SYSTEM EVOLVES BUT STRONG NORTHERLY FLOW
BEHIND IT COULD BRING THE COOLEST AIR WE HAVE SEEN IN SOME TIME
(850MB TEMPS POTENTIALLY BELOW 10C).
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 630 AM EDT MON AUG 17 2026
SHOWERS HAVE CLEARED KFWA BUT THE TERMINAL IS RIGHT ON THE EDGE
OF SOME IFR CEILINGS AND HI-RES GUIDANCE SUGGESTS THESE LOWER
CEILINGS COULD STILL IMPACT KFWA THROUGH ROUGHLY 14Z. CONFIDENCE
IN IFR IS LOW BUT MVFR IS LIKELY FOR A TIME THIS MORNING AS
MIXING RAMPS UP AMID PLENTIFUL BOUNDARY LAYER MOISTURE. MVFR
ALSO POSSIBLE AT KSBN AS WELL THOUGH CONFIDENCE IS LOWER THERE.
VFR RETURNS BY THE AFTERNOON AND TRANQUIL AVIATION CONDITIONS
ARE EXPECTED FOR THE SECOND HALF OF THE PERIOD.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...AGD
AVIATION...AGD
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