574
FXUS63 KIWX 171040
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
640 AM EDT WED JUN 17 2026
KEY MESSAGES
- TWO ROUNDS OF STORMS ARE EXPECTED TODAY (1-5PM EDT AND
5PM-12AM EDT). THERE IS A LOW CHANCE OF SEVERE WEATHER WITH
THE FIRST ROUND AND A MUCH HIGHER CHANCE WITH THE SECOND
ROUND.
- ALL HAZARDS WILL BE POSSIBLE ACROSS THE ENTIRE AREA WITH ROUND
2 INCLUDING STRONG TORNADOES, LARGE HAIL, DAMAGING WINDS AND
FLOODING. A FLOOD WATCH IS IN EFFECT FOR AREAS ALONG AND NORTH
OF US-24.
- QUIET WEATHER IS EXPECTED THURSDAY THROUGH SATURDAY.
DISCUSSION
ISSUED AT 308 AM EDT WED JUN 17 2026
ALL FOCUS IS ON POTENTIAL SEVERE WEATHER/FLOODING THREAT LATER
TODAY. THE STAGE IS SET FOR WIDESPREAD AND/OR SIGNIFICANT SEVERE
WEATHER BUT UNFORTUNATELY THERE ARE A FEW POSSIBLE FAILURE POINTS
THAT REDUCE CONFIDENCE. A SEASONABLY STRONG 130+ KT UPPER JET WILL
MOVE INTO THE SOUTHERN GREAT LAKES LATER TODAY, CARVING OUT AN
IMPRESSIVE PV ANOMALY (BY JUNE STANDARDS) OVER MICHIGAN.
CORRESPONDING TIGHTENING OF THE LOW-MID LEVEL GRADIENT OCCURS AS
WELL WITH WINDS SPEEDS ALL THE WAY FROM 850 TO 500MB SOLIDLY AT OR
ABOVE 75 KTS. A STRONG SURGE OF WARM/MOIST AIR ADVECTION ARRIVES BY
MIDDAY AND THIS WILL BRING THE FIRST ROUND OF STORMS ROUGHLY 16-21Z.
THERE WILL BE A SEVERE RISK FOR THIS FIRST ROUND BUT IT WILL DEPEND
ON EXACT TIMING. SOME CAM'S SHOW AN EARLIER ARRIVAL (16-18Z) WITH
CONVECTION OUTPACING THE BETTER FORCING FOR ASCENT AND LIMITING
DIURNAL INSTABILITY BUT SOME CAM'S SUGGEST AN ARRIVAL CLOSER TO 19-
21Z WHICH WOULD FEATURE BETTER MOISTURE CONVERGENCE/INSTABILITY AND
MID/UPPER LEVEL SUPPORT. DAMAGING WINDS WOULD BE THE MAIN CONCERN
BUT ISOLATED HAIL AND TORNADOES CAN'T BE RULED OUT WITH THIS ROUND
EITHER.
MAIN SEVERE WEATHER FOCUS REMAINS ON ROUND 2 THIS EVENING AS SURFACE
LOW/COLD FRONT CROSS THE AREA. HARD TO REMEMBER A TIME WITH A MORE
FAVORABLE HODOGRAPH FOR SIGNIFICANT TORNADOES IN THIS AREA WITH
BACKED SURFACE WIND AND NEARLY 70 KT FLOW A MERE 1 KM UP. 0-1KM
HELICITY VALUES COULD EASILY EXCEED 500 M2/S2. FURTHER, LCL'S MAY BE
AS LOW AS 500M PER MOST FORECAST SOUNDINGS. INSTABILITY,
PARTICULARLY IN THE LOW LEVELS, WILL BE THE KEY FEATURE TO MONITOR
AND WILL DICTATE THE LOCATION AND SEVERITY OF STORMS. THIS ASPECT OF
THE FORECAST IS LOWER CONFIDENCE, ESPECIALLY IN LIGHT OF 00Z
GUIDANCE. THE BETTER MIDLEVEL LAPSE RATES NOW LOOK TO BYPASS US TO
THE SOUTH (AND STILL ONLY 7 C/KM AT BEST). IMPRESSIVE LOW LEVEL
MOISTURE SURGE COMPENSATES FOR LACKLUSTER MIDLEVEL LAPSE RATES BUT
SOME FORECAST SOUNDINGS ARE LOOKING AWFULLY STABLE, PARTICULARLY IN
THE LOWEST 1-3KM, WHICH WOULD LIMIT THE SEVERE THREAT. HOWEVER, AS
WE KNOW AROUND HERE, IT DOESN'T TAKE MUCH INSTABILITY AT ALL TO
GENERATE TORNADOES GIVEN IMPRESSIVE KINEMATICS, LOW LCL'S, STRONG
SYNOPTIC SUPPORT, AND A BOUNDARY IN THE VICINITY. THIS WILL BE A DAY
OF CLOSELY MONITORING THE MESOSCALE ENVIRONMENT AND MUCH WILL DEPEND
ON THE EXACT TIMING AND EVOLUTION OF ROUND 1. WHILE SOME FAILURE
POINTS EXIST, IT IS IMPORTANT TO REMAIN VIGILANT GIVEN THE POTENTIAL
FOR STRONG TORNADOES. ALSO, WHILE THE HIGHEST TORNADO PROBABILITIES
REMAIN SOUTH OF US-30 AND WEST OF I-69 WHERE BETTER INSTABILITY
RESIDES, THE WARM FRONT LOCATION NEAR THE MICHIGAN BORDER (AND
PERHAPS EVEN FURTHER NORTH) WILL NEED TO BE WATCHED VERY CLOSELY AS
BETTER HELICITY EXISTS THERE AND THE TORNADO THREAT COULD BE JUST AS
HIGH OR HIGHER IF ANY MINOR INSTABILITY DEVELOPS THERE. TIMING
APPEARS TO BE ROUGHLY 21-04Z. IN ADDITION TO THE TORNADO THREAT,
WILL ALSO HAVE TO WATCH POTENTIAL FOR WAKE LOW DEVELOPMENT
WHICH COULD BRING DAMAGING WINDS BEHIND THE LINE OF STORMS INTO
THE LATE EVENING. REGARDLESS OF WAKE LOW DEVELOPMENT, IT WILL BE
BREEZY INTO THE OVERNIGHT AND ON THURSDAY. HAIL THREAT IS A BIT
LOWER GIVEN POOR LAPSE RATES BUT ANY ORGANIZED SUPERCELL WILL
STILL BE CAPABLE OF GENERATING SOME LARGE HAIL.
ALSO OF CONCERN IS THE POSSIBILITY OF HEAVY RAIN/FLOODING GIVEN THE
POTENTIAL FOR MULTIPLE ROUNDS OF CONVECTION TRAINING EAST-WEST
ACROSS THE AREA TODAY. PW VALUES REACH OR EXCEED 2 INCHES WITH A
VERY MOIST PROFILE THROUGHOUT THE COLUMN. WARM CLOUD LAYERS AND MBE
VELOCITIES ARE ON THE MARGINAL SIDE FOR A SIGNIFICANT FLOODING
THREAT AND STORM MOTIONS WILL BE FAST. HOWEVER, STILL SEE POTENTIAL
FOR A QUICK 2-3 INCHES IN SOME LOCATIONS (PARTICULARLY IN OUR NW)
AND THIS WILL BE CAPABLE OF AT LEAST ISOLATED POCKETS OF FLOODING
AND IMPACTS. HAVE THEREFORE ISSUED A FLOOD WATCH FOR AREAS ALONG AND
NORTH OF US-24. (FLOOD RISK APPEARS A BIT LOWER SOUTH OF 24).
OUTSIDE OF SOME GUSTY WINDS TOMORROW, NO WEATHER CONCERNS FOR
THURSDAY-SATURDAY. ANOTHER SYSTEM APPEARS POSSIBLE ON SUNDAY BUT
FOCUS REMAINED ON TODAY'S HAZARDS.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 640 AM EDT WED JUN 17 2026
STRONG WARM/MOIST AIR ADVECTION AHEAD OF APPROACHING TROUGH WILL
BRING WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS THIS
AFTERNOON AND EVENING. THE BEST CHANCES STILL APPEAR WITH THE
COLD FRONT DURING THE EVENING HOURS BUT THUNDER CHANCES ARE
INCREASING FOR THE FIRST ROUND AND A TEMPO MAY BE NECESSARY
(HOLDING PROB30 FOR NOW). STRONG WINDS AND BRIEF IFR CONDITIONS
ARE LIKELY WITH THESE STORMS. RETURN TO VFR EXPECTED OVERNIGHT
BUT BREEZY CONDITIONS WILL PERSIST.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FLOOD WATCH FROM 2 PM EDT /1 PM CDT/ THIS AFTERNOON THROUGH
LATE TONIGHT FOR INZ005>009-012>015-017-018-020-022>025-
103-104-116-203-204-216.
OH...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT
FOR OHZ001-002-004-005-015.
MI...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT
FOR MIZ078>081-177-277.
MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 4 PM EDT
THURSDAY FOR LMZ043-046.
DISCUSSION...AGD
AVIATION...AGD
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