736
FXUS63 KIWX 190756
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
356 AM EDT SAT JUL 19 2025
KEY MESSAGES
- SHOWERS AND THUNDERSTORM CHANCES WILL INCREASE THIS AFTERNOON
AND EVENING (MAINLY BETWEEN 1 AND 7 PM EDT). SOME STORMS COULD
BE SEVERE ESPECIALLY SOUTH OF US-30 WITH DAMAGING WINDS BEING
THE MAIN CONCERN. PROGRESSIVE NATURE SHOULD LIMIT OVERALL
FLOODING THREAT TO LOCALIZED INSTANCES OF FLOODING.
- ADDITIONAL SHOWER AND THUNDERSTORM CHANCES EXIST LATER TONIGHT
INTO SUNDAY EVENING, BUT CONFIDENCE IN AREAS MOST LIKELY TO BE
IMPACTED IS LOW AS INFLUENCE OF TODAY'S STORMS AND FINAL
FRONTAL POSITION WILL BE KEY.
- A SIGNIFICANT PERIOD OF DANGEROUS HEAT AND HUMIDITY IS
EXPECTED TO BUILD IN FROM THE MIDDLE TO THE END OF NEXT WEEK,
WITH HEAT INDICES IN EXCESS OF 100 DEGREES ANTICIPATED.
DISCUSSION
ISSUED AT 355 AM EDT SAT JUL 19 2025
SHOWERS AND STORMS HAVE BEEN IMPACTING SOUTHERN MN INTO N WI THE
PAST SEVERAL HOURS. THE MOST ORGANIZED AREA HAS REMAINED FOCUSED
IN SOUTHERN MN WHERE LOW 70 DEWPOINTS ARE FEEDING INTO THE
CLUSTER OF STORMS. MODELS HAVE STRUGGLED TO HANDLE THE OVERALL
EVOLUTION OF THE UPSTREAM CONVECTION, WITH HRRR FINALLY SEEMING
TO HAVE CAUGHT ON TO THE OVERALL SCENARIO. THIS AREA OF STORMS
IS LIKELY TO DRIFT ESE ALONG THE CAPE/THETA-E GRADIENT. THUS
FAR THESE HAVE BEEN SUB-SEVERE, WITH SOME POTENTIAL FOR UPSCALE
GROWTH WITH TIME AS IT MOVES ACROSS NE IOWA THROUGH 12Z AS NOTED
IN THE MOST RECENT SWOMCD. HAVE TRIMMED POPS CONSIDERABLY
THROUGH 15Z. CURRENT ALIGNMENT OF LIKELY POPS IS ORIENTED MORE
SW TO NE AND PROGRESSIVE ACROSS THE CWA, BUT ANTICIPATED
LOCATION OF THE INSTABILITY GRADIENT AND TRENDS IN HRRR SUGGEST
SW THIRD TO HALF OF THE AREA (ROUGHLY US-30 SOUTH AND EAST) MAY
HAVE THE BEST CHANCE FOR A LINE OF STRONG TO SEVERE STORMS AS IT
ARRIVES DURING PEAK HEATING. SLIGHT RISK WAS MAINTAINED BY SPC
FOR THE ENTIRE AREA, BUT COULD SEE SOME CHANGES IN LATER
OUTLOOKS TO FOCUS THE GREATEST THREAT TO THE AREA NOTED ABOVE.
LOCALLY HEAVY RAIN WILL REMAIN A CONCERN, BUT PROGRESSIVE NATURE
SHOULD LIMIT OVERALL FLOODING POTENTIAL. A WEAK FRONT WILL
DROP SOUTH INTO THE AREA TONIGHT INTO SUNDAY WITH YET ANOTHER
GRADIENT IN MOISTURE SETTING UP. INHERITED LIKELY POPS IN THE
SOUTH HAVE BEEN CAPPED AT UPPER CHANCE GIVEN AN INCREASING
LIKIHOOD THAT THE FURTHER SW TRACK OF STORMS THIS AFTERNOON WILL
EFFECTIVELY LIMIT CHANCES OVERNIGHT.
EFFECTIVE BOUNDARY WILL LIKELY REMAIN ACROSS PORTIONS OF CENTRAL
IL AND IN SUNDAY, WITH THE BULK OF NEW STORM DEVELOPMENT LIKELY
TO RESIDE IN THESE AREAS. FAR SOUTHERN COUNTIES REMAIN CLIPPED
BY A MARGINAL RISK FOR SEVERE ON DY2 WITH AXIS OF EXCESSIVE
RAINFALL ALSO SOUTH OF THE AREA. WHILE SKEPTICAL ON INHERITED
LIKELY POPS THROUGH THE DAY, WILL LEAVE THEM ALONE TO SEE WHAT
TRANSPIRES OVER THE NEXT 24 HOURS WRT TO THE BEST AXIS FOR
STORMS.
UPPER LEVEL FLOW BEGINS TO FLATTEN, BRIEFLY FOR MONDAY AND
TUESDAY WITH SEASONABLE TEMPERATURES AND MOST LIKELY DRY
CONDITIONS. EXPANSIVE UPPER LEVEL RIDGE WILL THEN BEGIN ITS PUSH
NORTH, INTRODUCING A PERIOD OF INCREASINGLY HOT AND HUMID
CONDITIONS FOR MAINLY WED AND THUR WITH HIGHS NEAR OR ABOVE 90
AND HEAT INDICES OF 100 DEGREES OR HIGHER. CAN'T RULE OUT A
STRAY STORM OR 2 IN WHAT WILL BE A VERY UNSTABLE, BUT LIKELY
CAPPED ENVIRONMENT. MODELS DISAGREE ON HOW SOON THE RIDGE WILL
FLATTEN IN THE FRI TO SAT TIME FRAME.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 157 AM EDT SAT JUL 19 2025
PREDOMINANTLY VFR CONDITIONS TO START THE TAF PERIOD, OUTSIDE OF
IFR VISIBILITIES POSSIBLE WITH ANY BR DEVELOPMENT AT KFWA
TONIGHT. IT'S POSSIBLE KSBN GOES MVFR LATE, BUT MOST OF THE
GUIDANCE KEEPS THE VISIBILITY HIGH-END MVFR OR DON'T DEVELOP ANY
BR AT ALL. WILL MONITOR TRENDS AND AMEND AS NEEDED. WINDS WILL
BE LIGHT AND SOMEWHAT VARIABLE THROUGH THE OVERNIGHT PERIOD.
SHOWERS AND THUNDERSTORMS MAY IMPACT BOTH TERMINALS FOR THE
AFTERNOON AND EVENING, FIRST AT KSBN (17-18Z ISH) AND THEN AT
KFWA (BEST POTENTIAL AROUND 21Z). SOME OF THE MODELS BRING IN A
LINE OF STORMS THAT CROSS FROM WEST TO EAST WITH POTENTIAL FOR
SEVERE WIND GUSTS, BUT OTHERS SUGGEST THE STORMS WILL BE MORE
SCATTERED AND IT COULD BE HIT AN MISS FOR THE TERMINALS (STILL
POTENTIAL FOR SEVERE GUSTS). FOR NOW, USED TEMPOS AND PROB30
GROUPS TO IDENTIFY THE MOST LIKELY TIMES, WITH IFR/MVFR
VISIBILITIES LIKELY IN ANY STORMS, AND A WIND SHIFT TO THE WNW-
ESPECIALLY IF IT'S MORE OF A LINE OF STORMS. HAVE GUSTS TO 30
KNOTS NOW IN THE TEMPO GROUPS GIVEN UNCERTAINTIES WITH THE
NATURE OF THE STORM TYPE/COVERAGE, WITH MVFR CEILINGS.
WINDS LIGHTEN UP AND BECOME SOMEWHAT VARIABLE BEHIND THE STORMS,
WITH POTENTIAL FOR SHOWERS TO LINGER INTO THE EVENING. SOME OF
THE GUIDANCE CLEARS ALL SHOWER/STORM ACTIVITY FROM THE TERMINALS
BY 00Z, BUT OTHERS LINGER WITH CHANCES (ESPECIALLY AT KFWA)
UNTIL AROUND 3Z. WILL ADD FURTHER DETAIL ON THAT WITH THE 12Z
TAF CYCLE.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...FISHER
AVIATION...MCD
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