543
FXUS63 KIWX 190608
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
208 AM EDT SAT JUL 19 2025
KEY MESSAGES
- STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED SATURDAY
AFTERNOON AND EVENING, WITH DAMAGING WINDS AS THE PRIMARY
THREAT.
- LOCALLY HEAVY RAINFALL FROM SATURDAY'S STORMS COULD LEAD TO
ISOLATED INSTANCES OF FLOODING, THOUGH THE PROGRESSIVE NATURE
OF THE STORMS MAY LIMIT A MORE WIDESPREAD THREAT.
- 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 115 PM EDT FRI JUL 18 2025
A QUIET AND PLEASANT DAY IS ON TAP FOR THE CWA TODAY AS HIGH
PRESSURE PROVIDES US WITH DRY CONDITIONS AND A TOUCH LOWER
HUMIDITY. THIS WILL BE SHORT-LIVED, HOWEVER, AS SOUTHERLY FLOW
DEVELOPS TONIGHT, ADVECTING MUCH WARMER/HUMID AIRMASS THAT WILL
SET THE STAGE FOR AN ACTIVE SATURDAY.
THE PRIMARY CHALLENGE IN THE NEAR TERM IS A MULTI-HAZARD EVENT
ON SATURDAY, AS THE AREA WILL RESIDE UNDER A VERY UNSTABLE AND
MOISTURE- RICH ENVIRONMENT OUT AHEAD OF AN APPROACHING COLD
FRONT. SPC HAS PLACED THE ENTIRE AREA UNDER A SLIGHT RISK (LEVEL
2 OF 5) FOR SEVERE THUNDERSTORMS. THE MAIN TIME TO WATCH IS
FROM 12 TO 6PM, BUT STORMS MAY OCCUR AN HOUR OR TWO ON EITHER
SIDE OF THAT. AMPLE INSTABILITY IS FORECAST, WITH HREF
SUGGESTING CAPE VALUES AROUND 2,000 J/KG. THIS WILL COMBINE
WITH MARGINALLY SUFFICIENT WIND SHEAR TO SUPPORT AN ORGANIZED
LINE OF STRONG TO SEVERE STORMS MOVING THROUGH THE AREA DURING
THE PM HOURS. THE MAIN THREAT WILL BE DAMAGING WINDS, BUT
SECONDARY THREATS INCLUDE SMALL HAIL AND A LOW-END CHANCE FOR
LINE- EMBEDDED TORNADOES.
IN ADDITION TO THE SEVERE THREAT, VERY HIGH MOISTURE CONTENT
CHARACTERIZED BY PWATS APPROACHING 2IN WILL LEAD TO A THREAT OF
HEAVY RAINFALL. CONSEQUENTLY, WE HAVE ALSO BEEN PLACED UNDER A
SLIGHT RISK FOR EXCESSIVE RAINFALL BY WPC. STORMS WILL BE
CAPABLE OF PRODUCING TORRENTIAL DOWNPOURS THAT COULD LEAD TO
ISOLATED FLOODING. HOWEVER, THE EXPECTED PROGRESSIVE STORM MODE
SHOULD HELP LIMIT A MORE WIDESPREAD FLOODING THREAT.
SIGNIFICANT UNCERTAINTY REMAINS REGARDING THE IMPACT OF ANY
POTENTIAL MORNING CONVECTION. IF WIDESPREAD SHOWERS AND STORMS
FORM IN THE MORNING, THEY COULD STABILIZE THE ATMOSPHERE AND
LIMIT THE AFTERNOON STORM POTENTIAL, A COMMON FORECAST PROBLEM
IN THE MIDWEST.
COOLER AND DRIER AIR WILL FILTER IN BEHIND THE FRONT FOR
SUN/MON, PROVIDING A BRIEF BREAK FROM THE ACTIVE WEATHER. DURING
THIS SUNDAY THROUGH TUESDAY TIMEFRAME, TRENDS SUGGEST THAT ANY
ORGANIZED COMPLEXES OF STORMS WILL REMAIN JUST TO THE SOUTH AND
WEST OF OUR REGION, ALTHOUGH THIS WILL NEED TO BE MONITORED -
ESPECIALLY FOR SUNDAY WHERE CONFIDENCE IN NORTHERN EXTENT OF
PRECIPITATION IS STILL A BIT UNCERTAIN.
THE FOCUS THEN SHIFTS TO A MAJOR PATTERN CHANGE FOR THE MIDDLE
AND END OF NEXT WEEK. THERE IS HIGH CONFIDENCE THAT A STRONG
UPPER-LEVEL RIDGE WILL BUILD ACROSS THE CENTRAL US AND TAKE HOLD
OVER OUR REGION. THIS WILL BRING A PROLONGED PERIOD OF
DANGEROUS HEAT AND HUMIDITY, LIKELY FROM WEDNESDAY THROUGH NEXT
WEEKEND. HIGH TEMPERATURES ARE EXPECTED TO BE NEAR OR ABOVE 90
DEGREES WITH DEWPOINTS IN THE 70S, LEADING TO POTENTIALLY
DANGEROUS HEAT INDICES IN EXCESS OF 100 DEGREES. THIS HEAT DOME
PATTERN WILL ESTABLISH A RING OF FIRE CONVECTIVE REGIME WITH
STORM COMPLEXES RIDING ALONG THE NORTHERN EDGE OF THE RIDGE,
BRINGING PERIODIC RAIN CHANCES BACK INTO THE FORECAST FOR THE
LATTER PART OF THE WEEK.
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...NORMAN
AVIATION...MCD
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